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van den Busch, J. L., H. Hildebrandt, A. H. Wright, C. B. Morrison, C. Blake, B. Joachimi, T. Erben, C. Heymans, K. Kuijken, and E. N. Taylor. "Testing KiDS cross-correlation redshifts with simulations." Astronomy & Astrophysics 642 (October 2020): A200. http://dx.doi.org/10.1051/0004-6361/202038835.
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Measuring cosmic shear in wide-field imaging surveys requires accurate knowledge of the redshift distribution of all sources. The clustering-redshift technique exploits the angular cross-correlation of a target galaxy sample with unknown redshifts and a reference sample with known redshifts. It represents an attractive alternative to colour-based methods of redshift calibration. Here we test the performance of such clustering redshift measurements using mock catalogues that resemble the Kilo-Degree Survey (KiDS). These mocks are created from the MICE simulation and closely mimic the properties of the KiDS source sample and the overlapping spectroscopic reference samples. We quantify the performance of the clustering redshifts by comparing the cross-correlation results with the true redshift distributions in each of the five KiDS photometric redshift bins. Such a comparison to an informative model is necessary due to the incompleteness of the reference samples at high redshifts. Clustering mean redshifts are unbiased at |Δz|< 0.006 under these conditions. The redshift evolution of the galaxy bias of the reference and target samples represents one of the most important systematic errors when estimating clustering redshifts. It can be reliably mitigated at this level of precision using auto-correlation measurements and self-consistency relations, and will not become a dominant source of systematic error until the arrival of Stage-IV cosmic shear surveys. Using redshift distributions from a direct colour-based estimate instead of the true redshift distributions as a model for comparison with the clustering redshifts increases the biases in the mean to up to |Δz|∼0.04. This indicates that the interpretation of clustering redshifts in real-world applications will require more sophisticated (parameterised) models of the redshift distribution in the future. If such better models are available, the clustering-redshift technique promises to be a highly complementary alternative to other methods of redshift calibration.
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Percival, Will J., Lado Samushia, Ashley J. Ross, Charles Shapiro, and Alvise Raccanelli. "Redshift-space distortions." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 369, no. 1957 (December 28, 2011): 5058–67. http://dx.doi.org/10.1098/rsta.2011.0370.
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Comparing measurements of redshift-space distortions (RSDs) with geometrical observations of the expansion of the Universe offers tremendous potential for testing general relativity on very large scales. The basic linear theory of RSDs in the distant-observer limit has been known for 25 years and the effect has been conclusively observed in numerous galaxy surveys. The next generation of galaxy survey will observe many millions of galaxies over volumes of many tens of Gpc 3 . They will provide RSD measurements of such exquisite precision that we will have to carefully analyse and correct for many systematic deviations from this simple picture in order to fully exploit the statistical precision obtained. We review RSD theory and show how ubiquitous RSDs actually are, and then consider a number of potential systematic effects, shamelessly highlighting recent work in which we have been involved. This review ends by looking ahead to the future surveys that will make the next generation of RSD measurements.
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Ruggeri, Rossana, Will J. Percival, Héctor Gil-Marín, Fangzhou Zhu, Gong-Bo Zhao, and Yuting Wang. "Optimal redshift weighting for redshift-space distortions." Monthly Notices of the Royal Astronomical Society 464, no. 3 (September 23, 2016): 2698–707. http://dx.doi.org/10.1093/mnras/stw2422.
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Turner, Ross J., Guillaume Drouart, Nick Seymour, and Stanislav S. Shabala. "RAiSERed: radio continuum redshifts for lobed active galactic nuclei." Monthly Notices of the Royal Astronomical Society 499, no. 3 (October 6, 2020): 3660–72. http://dx.doi.org/10.1093/mnras/staa3067.
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ABSTRACT Next-generation radio surveys are expected to detect tens of millions of active galactic nuclei (AGNs) with a median redshift of $z$ ≥ 1. Beyond targeted surveys, the vast majority of these objects will not have spectroscopic redshifts, while photometric redshifts for high-redshift AGNs are of limited quality, and even then require optical and infrared photometry. We propose a new approach to measure the redshifts of lobed radio galaxies based exclusively on radio-frequency imaging and broad-band radio photometry. Specifically, our algorithm uses the lobe flux density, angular size and width, and spectral shape to derive probability density functions for the most likely source redshift based on the Radio AGN in Semi-analytic Environments dynamical model. The full physically based model explains 70 per cent of the variation in the spectroscopic redshifts of a high-redshift (2 < $z$ < 4) sample of radio AGNs, compared to at most 27 per cent for any one of the observed attributes in isolation. We find that upper bounds on the angular size, as expected for unresolved sources, are sufficient to yield accurate redshift measurements at $z$ ≥ 2. The error in the model upon calibration using at least nine sources with known spectroscopic redshifts is <14 per cent in redshift (as 1 + $z$) across all redshifts. We provide the python code for the calculation and calibration of our radio continuum redshifts in an online library.
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Shepherd, C. W., R. G. Carlberg, H. K. C. Yee, and E. Ellingson. "The Real Space and Redshift Space Correlation Functions at Redshiftz= 1/3." Astrophysical Journal 479, no. 1 (April 10, 1997): 82–89. http://dx.doi.org/10.1086/303846.
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García-Farieta, Jorge Enrique, Federico Marulli, Alfonso Veropalumbo, Lauro Moscardini, Rigoberto A. Casas-Miranda, Carlo Giocoli, and Marco Baldi. "Clustering and redshift-space distortions in modified gravity models with massive neutrinos." Monthly Notices of the Royal Astronomical Society 488, no. 2 (July 8, 2019): 1987–2000. http://dx.doi.org/10.1093/mnras/stz1850.
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Abstract Modified gravity and massive neutrino cosmologies are two of the most interesting scenarios that have been recently explored to account for possible observational deviations from the concordance Λ cold dark matter (ΛCDM) model. In this context, we investigated the large-scale structure of the Universe by exploiting the dustgrain-pathfinder simulations that implement, simultaneously, the effects of f(R) gravity and massive neutrinos. To study the possibility of breaking the degeneracy between these two effects, we analysed the redshift-space distortions in the clustering of dark matter haloes at different redshifts. Specifically, we focused on the monopole and quadrupole of the two-point correlation function, both in real and redshift space. The deviations with respect to ΛCDM model have been quantified in terms of the linear growth rate parameter. We found that redshift-space distortions provide a powerful probe to discriminate between ΛCDM and modified gravity models, especially at high redshifts (z ≳ 1), even in the presence of massive neutrinos.
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Brisbin, Drew, Oskari Miettinen, Manuel Aravena, Vernesa Smolčić, Ivan Delvecchio, Chunyan Jiang, Benjamin Magnelli, et al. "An ALMA survey of submillimeter galaxies in the COSMOS field: Multiwavelength counterparts and redshift distribution." Astronomy & Astrophysics 608 (November 29, 2017): A15. http://dx.doi.org/10.1051/0004-6361/201730558.
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We carried out targeted ALMA observations of 129 fields in the COSMOS region at 1.25 mm, detecting 152 galaxies at S/N ≥ 5 with an average continuum RMS of 150 μJy. These fields represent a S/N-limited sample of AzTEC/ASTE sources with 1.1 mm S/N ≥ 4 over an area of 0.72 square degrees. Given ALMA’s fine resolution and the exceptional spectroscopic and multiwavelength photometric data available in COSMOS, this survey allows us unprecedented power in identifying submillimeter galaxy counterparts and determining their redshifts through spectroscopic or photometric means. In addition to 30 sources with prior spectroscopic redshifts, we identified redshifts for 113 galaxies through photometric methods and an additional nine sources with lower limits, which allowed a statistically robust determination of the redshift distribution. We have resolved 33 AzTEC sources into multi-component systems and our redshifts suggest that nine are likely to be physically associated. Our overall redshift distribution peaks at z ~ 2.0 with a high-redshift tail skewing the median redshift to \hbox{$\tilde{z}=2$}.48 ± 0.05. We find that brighter millimeter sources are preferentially found at higher redshifts. Our faintestsources, with S1.25 mm < 1.25 mJy, have a median redshift of \hbox{$\tilde{z}=2$}.18 ± 0.09, while the brightest sources, S1.25 mm > 1.8 mJy, have a median redshift of \hbox{$\tilde{z}=3$}.08 ± 0.17. After accounting for spectral energy distribution shape and selection effects, these results are consistent with several previous submillimeter galaxy surveys, and moreover, support the conclusion that the submillimeter galaxy redshift distribution is sensitive to survey depth.
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Sandhu, Gurcharn S. "Distinct Doppler Effects for Spontaneously Emitted Photons and Continuously Emitted Waves." Applied Physics Research 9, no. 4 (July 26, 2017): 44. http://dx.doi.org/10.5539/apr.v9n4p44.
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In this paper, we distinguish between the Doppler effects for spontaneously emitted photons and continuously emitted waves. Under certain plausible assumptions, electron orbits can be modeled for simple atomic systems and such studies show that all permissible electron trajectories correspond to elliptical orbits. From the conservation of energy, momentum and angular momentum, in conjunction with the geometrical model of electron orbits, we derive the Doppler effect for spontaneously emitted photons that is quite different from the one used for continuously generated waves. All astronomical redshifts are currently interpreted by assuming the incoming radiation to be continuously emitted waves. Therefore, widely-observed redshift in radiation from most astronomical sources is interpreted to imply the expanding universe, along with cosmological expansion of space. However, for the spontaneously emitted photons, we show that the photons emitted in forward direction parallel to the emitter velocity get redshifted. That means, the astronomical redshift implies that the emission sources are moving towards the observer and our universe is not expanding. All high redshift astronomical objects are likely to be physically disrupted through dynamic instabilities or explosions and their high redshifts are associated with relativistic shock waves propagating towards the observer. Hence the proposed Doppler effect for the spontaneously emitted photons dismisses the cosmological expansion of space and supports a steady state universe.
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Sicilian, Dominic, Francesca Civano, Nico Cappelluti, Johannes Buchner, and Alessandro Peca. "X-Ray Redshifts of Obscured Chandra Source Catalog Active Galactic Nuclei." Astrophysical Journal 936, no. 1 (August 29, 2022): 39. http://dx.doi.org/10.3847/1538-4357/ac82f4.
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Abstract We have computed obscured active galactic nuclei (AGN) redshifts using the XZ method, adopting a broad treatment in which we employed a wide-ranging data set and worked primarily at the XZ counts sensitivity threshold, culminating with a redshift catalog containing 121 sources that lack documented redshifts. We considered 363 obscured AGN from the Chandra Source Catalog Release 2.0, 59 of which were selected using multiwavelength criteria while 304 were X-ray selected. One third of the data set had crossmatched spectroscopic or photometric redshifts. These sources, dominated by low-z and low-N H AGN, were supplemented by 1000 simulations to form a data set for testing the XZ method. We used a multilayer perceptron neural network to examine and predict cases in which XZ fails to reproduce the known redshift, yielding a classifier that can identify and discard poor redshift estimates. This classifier demonstrated a statistically significant ∼3σ improvement over the existing XZ redshift information gain filter. We applied the machine-learning model to sources with no documented redshifts, resulting in the 121 source new redshift catalog, all of which were X-ray selected. Our neural network’s performance suggests that nearly 90% of these redshift estimates are consistent with hypothetical spectroscopic or photometric measurements, strengthening the notion that redshifts can be reliably estimated using only X-rays, which is valuable to current and future missions such as Athena. We have also identified a possible Compton-thick candidate that warrants further investigation.
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Fauber, Leah, Ming-Feng Ho, Simeon Bird, Christian R. Shelton, Roman Garnett, and Ishita Korde. "Automated measurement of quasar redshift with a Gaussian process." Monthly Notices of the Royal Astronomical Society 498, no. 4 (September 18, 2020): 5227–39. http://dx.doi.org/10.1093/mnras/staa2826.
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ABSTRACT We develop an automated technique to measure quasar redshifts in the Baryon Oscillation Spectroscopic Survey of the Sloan Digital Sky Survey (SDSS). Our technique is an extension of an earlier Gaussian process method for detecting damped Lyman α absorbers (DLAs) in quasar spectra with known redshifts. We apply this technique to a subsample of SDSS DR12 with BAL quasars removed and redshift larger than 2.15. We show that we are broadly competitive to existing quasar redshift estimators, disagreeing with the PCA redshift by more than 0.5 in only $0.38{{\ \rm per\ cent}}$ of spectra. Our method produces a probabilistic density function for the quasar redshift, allowing quasar redshift uncertainty to be propagated to downstream users. We apply this method to detecting DLAs, accounting in a Bayesian fashion for redshift uncertainty. Compared to our earlier method with a known quasar redshift, we have a moderate decrease in our ability to detect DLAs, predominantly in the noisiest spectra. The area under curve drops from 0.96 to 0.91. Our code is publicly available.
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Shuntov, M., J. Pasquet, S. Arnouts, O. Ilbert, M. Treyer, E. Bertin, S. de la Torre, et al. "PhotoWeb redshift: boosting photometric redshift accuracy with large spectroscopic surveys." Astronomy & Astrophysics 636 (April 2020): A90. http://dx.doi.org/10.1051/0004-6361/201937382.
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Improving distance measurements in large imaging surveys is a major challenge to better reveal the distribution of galaxies on a large scale and to link galaxy properties with their environments. As recently shown, photometric redshifts can be efficiently combined with the cosmic web extracted from overlapping spectroscopic surveys to improve their accuracy. In this paper we apply a similar method using a new generation of photometric redshifts based on a convolution neural network (CNN). The CNN is trained on the SDSS images with the main galaxy sample (SDSS-MGS, r ≤ 17.8) and the GAMA spectroscopic redshifts up to r ∼ 19.8. The mapping of the cosmic web is obtained with 680 000 spectroscopic redshifts from the MGS and BOSS surveys. The redshift probability distribution functions (PDF), which are well calibrated (unbiased and narrow, ≤120 Mpc), intercept a few cosmic web structures along the line of sight. Combining these PDFs with the density field distribution provides new photometric redshifts, zweb, whose accuracy is improved by a factor of two (i.e., σ ∼ 0.004(1 + z)) for galaxies with r ≤ 17.8. For half of them, the distance accuracy is better than 10 cMpc. The narrower the original PDF, the larger the boost in accuracy. No gain is observed for original PDFs wider than 0.03. The final zweb PDFs also appear well calibrated. The method performs slightly better for passive galaxies than star-forming ones, and for galaxies in massive groups since these populations better trace the underlying large-scale structure. Reducing the spectroscopic sampling by a factor of 8 still improves the photometric redshift accuracy by 25%. Finally, extending the method to galaxies fainter than the MGS limit still improves the redshift estimates for 70% of the galaxies, with a gain in accuracy of 20% at low z where the resolution of the cosmic web is the highest. As two competing factors contribute to the performance of the method, the photometric redshift accuracy and the resolution of the cosmic web, the benefit of combining cosmological imaging surveys with spectroscopic surveys at higher redshift remains to be evaluated.
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Bharadwaj, Somnath. "Radial Redshift Space Distortions." Astrophysical Journal 516, no. 2 (May 10, 1999): 507–18. http://dx.doi.org/10.1086/307118.
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Maitra, Soumak, Raghunathan Srianand, and Prakash Gaikwad. "Measurement of redshift-space two- and three-point correlation of Lyα absorbers at 1.7 < z < 3.5: implications on evolution of the physical properties of IGM." Monthly Notices of the Royal Astronomical Society 509, no. 1 (October 22, 2021): 1536–56. http://dx.doi.org/10.1093/mnras/stab3053.
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ABSTRACT We present redshift-space two-point (ξ), three-point (ζ), and reduced three-point (Q) correlation of Lyα absorbers (Voigt profile components having H i column density, NH i > 1013.5 cm−2) over three redshift bins spanning 1.7 < z < 3.5 using high-resolution spectra of 292 quasars. We detect positive ξ up to 8 h−1 cMpc in all three redshift bins. The strongest detection of ζ = 1.81 ± 0.59 (with Q = 0.68 ± 0.23) is in $z$ = 1.7–2.3 bin at 1–2 h−1 cMpc. The measured ξ and ζ values show an increasing trend with NH i, while Q remains relatively independent of NH i. We find ξ and ζ to evolve strongly with redshift. Using simulations, we find that ξ and ζ seen in real space may be strongly amplified by peculiar velocities in redshift space. Simulations suggest that while feedback, thermal and pressure smoothing effects influence the clustering of Lyα absorbers at small scales, i.e. <0.5 h−1 cMpc, the H i photoionization rate (ΓH i) has a strong influence at all scales. The strong redshift evolution of ξ and ζ (for a fixed NH i cut-off) is driven by the redshift evolution of the relationship between NH i and baryon overdensity. Our simulation using best-fitting ΓH i($z$) measurements produces consistent clustering signals with observations at $z$ ∼ 2 but underpredicts the clustering at higher redshifts. One possible remedy is to have higher values of ΓH i at higher redshifts. Alternatively the discrepancy could be related to non-equilibrium and inhomogeneous conditions prevailing during He ii reionization not captured by our simulations.
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Dai, Yan, Xiao-Gang Zheng, Zheng-Xiang Li, He Gao, and Zong-Hong Zhu. "Redshift evolution of the Amati relation: Calibrated results from the Hubble diagram of quasars at high redshifts." Astronomy & Astrophysics 651 (July 2021): L8. http://dx.doi.org/10.1051/0004-6361/202140895.
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Gamma-ray bursts (GRBs) have long been proposed as a complementary probe to type Ia supernovae (SNe Ia) and the cosmic microwave background to explore the expansion history of the high-redshift universe, mainly because they are bright enough to be detected at greater distances. Although they lack definite physical explanations, many empirical correlations between GRB isotropic energy or luminosity and some directly detectable spectral or temporal properties have been proposed to make GRBs standard candles. Since the observed GRB rate falls off rapidly at low redshifts, this thus prevents a cosmology independent calibration of these correlations. In order to avoid the circularity problem, SN Ia data are usually used to calibrate the luminosity relations of GRBs in the low redshift region (limited by the redshift range for SN Ia sample), and then they are extrapolate the luminosity relations to the high redshift region. This approach is based on the assumption of no redshift evolution for GRB luminosity relations. In this work, we suggest the use of a complete quasar sample in the redshift range of 0.5 < z < 5.5 to test such an assumption. We divided the quasar sample into several subsamples with different redshift bins, and used each subsample to calibrate the isotropic γ-ray equivalent energy of GRBs in relevant redshift bins. By fitting the newly calibrated data, we find strong evidence that the most commonly used Amati relation between spectral peak energy and isotropic-equivalent radiated energy shows no, or marginal, evolution with redshift. Indeed, at different redshifts, the coefficients in the Amati relation could have a maximum variation of 0.93% at different redshifts, and there could be no coincidence in the range of 1σ.
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Crampton, D., A. P. Cowley, and F. D. A. Hartwick. "The Space Distribution of Faint CFHT Quasars." Symposium - International Astronomical Union 124 (1987): 655. http://dx.doi.org/10.1017/s0074180900159698.
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The space distribution of quasars discovered in our CFHT blue grens survey is discussed in detail. Redshifts for about 200 of the quasar candidates show that the sample is relatively complete for 0.2 < z < 3.4 and m < 20.5. Two-thirds of the quasars have z < 1.8 and only 5% have z > 2.5, indicating that high redshift quasars are rare. The surface density of quasars brighter than m = 20.5 is 30 deg−2. Seven quasars with z = 1.165 ± 0.007 discovered in one of the fields have typical separations of ≈20 Mpc and may belong to a very large structure. Statistical tests on our data indicate that clustering among quasars is not common, however. The luminosity dependent density evolution models proposed by Schmidt and Green (1983) combined with a redshift cutoff at high redshift are consistent with our data and that of Schmidt and Green (1983), Marshall et al. (1984), Koo, Kron and Cudworth (1986), and Schmidt, Schneider and Gunn (1986). The model indicates that there was a broad maximum in the comoving density of quasars near z = 1.7. The results will be reported in detail in the March 1987 issue of The Astrophysical Journal.
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Abraham, R. G. "A Review of High-Redshift Merger Observations." Symposium - International Astronomical Union 186 (1999): 11–22. http://dx.doi.org/10.1017/s0074180900112148.
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Evolution in the merger rate as a function of redshift isin principlethe key observable testing hierarchical models for the formation and evolution of galaxies. However,in practice, direct measurement of this quantity has proven difficult. In this opening review I outline the current best estimates for the merger rate as a function of cosmic epoch, focusing mostly upon recent advances made possible by deep ground-based redshift surveys and morphological studies undertaken withHST.I argue that a marriage of these techniques, in an attempt to determine the space density of mergers amongst the abundant morphologically peculiar population at high redshifts, is probably the most promising currently-available avenue for determining the prevalence of mergers at high redshifts. However, resolved kinematical studies, which seem set to become available in the next few years, are probably the best hope for a definitive determination of the space density of mergers at high redshifts.
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Simmonds, C., J. Buchner, M. Salvato, L. T. Hsu, and F. E. Bauer. "XZ: Deriving redshifts from X-ray spectra of obscured AGN." Astronomy & Astrophysics 618 (October 2018): A66. http://dx.doi.org/10.1051/0004-6361/201833412.
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Context. Redshifts are fundamental for our understanding of extragalactic X-ray sources. Ambiguous counterpart associations, expensive optical spectroscopy, and/or multimission multiwavelength coverage to resolve degeneracies often make estimation difficult in practice. Aims. We attempt to constrain redshifts of obscured active galactic nuclei (AGN) using only low-resolution X-ray spectra. Methods. Our method for determining redshifts from the X-ray spectrum (XZ) fits AGN X-ray spectra with a moderately complex spectral model incorporating a corona, a torus obscurer, and a warm mirror. Using the Bayesian X-ray Astronomy (BXA) package, we constrain redshift, column density, photon index, and luminosity simultaneously. The redshift information primarily comes from absorption edges in Compton-thin AGN, and from the Fe Kα fluorescent line in heavily obscured AGN. A new generic background fitting method allows us to extract more information from limited numbers of source counts. Results. We derive redshift constraints for 74/321 hard-band detected sources in the Chandra deep field South. Comparing with spectroscopic redshifts, we find an outlier fraction of 8%, indicating that our model assumptions are valid. For three Chandra deep fields, we release our XZ redshift estimates. Conclusions. The independent XZ estimate is easy to apply and effective for a large fraction of obscured AGN in today’s deep surveys without the need for any additional data. Compared to different redshift estimation methods, XZ can resolve degeneracies in photometric redshifts, help detect potential association problems, and confirm uncertain single-line spectroscopic redshifts. With high spectral resolution and a large collecting area, this technique will be highly effective for Athena/WFI observations.
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Davis, Tamara M., Samuel R. Hinton, Cullan Howlett, and Josh Calcino. "Can redshift errors bias measurements of the Hubble Constant?" Monthly Notices of the Royal Astronomical Society 490, no. 2 (September 21, 2019): 2948–57. http://dx.doi.org/10.1093/mnras/stz2652.
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ABSTRACT Redshifts have been so easy to measure for so long that we tend to neglect the fact that they too have uncertainties and are susceptible to systematic error. As we strive to measure cosmological parameters to better than 1 per cent it is worth reviewing the accuracy of our redshift measurements. Surprisingly small systematic redshift errors, as low as 10−4, can have a significant impact on the cosmological parameters we infer, such as H0. Here, we investigate an extensive (but not exhaustive) list of ways in which redshift estimation can go systematically astray. We review common theoretical errors, such as adding redshifts instead of multiplying by (1 + z); using v = cz; and using only cosmological redshift in the estimates of luminosity and angular diameter distances. We consider potential observational errors, such as rest wavelength precision, air to vacuum conversion, and spectrograph wavelength calibration. Finally, we explore physical effects, such as peculiar velocity corrections, galaxy internal velocities, gravitational redshifts, and overcorrecting within a bulk flow. We conclude that it would be quite easy for small systematic redshift errors to have infiltrated our data and be impacting our cosmological results. While it is unlikely that these errors are large enough to resolve the current H0 tension, it remains possible, and redshift accuracy may become a limiting factor in near future experiments. With the enormous efforts going into calibrating the vertical axis of our plots (standard candles, rulers, clocks, and sirens) we argue that it is now worth paying a little more attention to the horizontal axis (redshifts).
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Walker, Charles R. H., Yin-Zhe Ma, and René P. Breton. "Constraining the redshifts of unlocalised fast radio bursts." Astronomy & Astrophysics 638 (June 2020): A37. http://dx.doi.org/10.1051/0004-6361/201833157.
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Context. The relationship between the dispersion measures (DMs) and redshifts of fast radio bursts (FRBs) is of scientific interest. Upcoming commensal surveys may detect and localise many FRBs to the sub-arcsecond angular resolutions required for accurate redshift determination. Meanwhile, it is important to exploit sources accumulated with more limited localisation to their maximum scientific potential. Aims. We present techniques for the DM-redshift analysis of large numbers of unlocalised FRBs, accounting for uncertainties due to their extragalactic DM components, redshift dependences, and progenitor scenarios. Methods. We reviewed the components comprising observed FRB DMs. We built redshift-scalable probability distribution functions for these components, which we combined in cases of multiple progenitor scenarios. Accounting for prior FRB redshift distributions we inverted these models, enabling FRB redshifts to be constrained. Results. We illustrate the influence of FRB progenitors on their observed DMs, which may remain significant to redshift z ~ 3. We identify the FRB sample sizes required to distinguish between multiple progenitor scenarios. We place new, physically motivated redshift constraints on all catalogued FRBs to date and use these to reject potential host galaxies in the localisation area of an FRB according to various models. We identify further uses for DM-redshift analysis using many FRBs. We provide our code so that these techniques may be employed using increasingly realistic models as our understanding of FRBs evolves.
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Wen, Z. L., and J. L. Han. "Photometric redshifts for galaxies in the Subaru Hyper Suprime-Cam and unWISE and a catalogue of identified clusters of galaxies." Monthly Notices of the Royal Astronomical Society 500, no. 1 (October 27, 2020): 1003–17. http://dx.doi.org/10.1093/mnras/staa3308.
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ABSTRACT We first present a catalogue of photometric redshifts for 14.68 million galaxies derived from the 7-band photometric data of Hyper Suprime-Cam Subaru Strategic Program and the Wide-field Infrared Survey Explorer using the nearest-neighbour algorithm. The redshift uncertainty is about 0.024 for galaxies of z ≤ 0.7, and steadily increases with redshift to about 0.11 at z ∼ 2. From such a large data set, we identify 21 661 clusters of galaxies, among which 5537 clusters have redshifts z > 1 and 642 clusters have z > 1.5, significantly enlarging the high redshift sample of galaxy clusters. Cluster richness and mass are estimated, and these clusters have an equivalent mass of M500 ≥ 0.7 × 1014 M⊙. We find that the stellar mass of the brightest cluster galaxies (BCGs) in each richness bin does not significantly evolve with redshift. The fraction of star-forming BCGs increases with redshift, but does not depend on cluster mass.
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Hildebrandt, H., J. L. van den Busch, A. H. Wright, C. Blake, B. Joachimi, K. Kuijken, T. Tröster, et al. "KiDS-1000 catalogue: Redshift distributions and their calibration." Astronomy & Astrophysics 647 (March 2021): A124. http://dx.doi.org/10.1051/0004-6361/202039018.
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We present redshift distribution estimates of galaxies selected from the fourth data release of the Kilo-Degree Survey over an area of ∼1000 deg2 (KiDS-1000). These redshift distributions represent one of the crucial ingredients for weak gravitational lensing measurements with the KiDS-1000 data. The primary estimate is based on deep spectroscopic reference catalogues that are re-weighted with the help of a self-organising map (SOM) to closely resemble the KiDS-1000 sources, split into five tomographic redshift bins in the photometric redshift range 0.1 < zB ≤ 1.2. Sources are selected such that they only occupy that volume of nine-dimensional magnitude-space that is also covered by the reference samples (‘gold’ selection). Residual biases in the mean redshifts determined from this calibration are estimated from mock catalogues to be ≲0.01 for all five bins with uncertainties of ∼0.01. This primary SOM estimate of the KiDS-1000 redshift distributions is complemented with an independent clustering redshift approach. After validation of the clustering-z on the same mock catalogues and a careful assessment of systematic errors, we find no significant bias of the SOM redshift distributions with respect to the clustering-z measurements. The SOM redshift distributions re-calibrated by the clustering-z represent an alternative calibration of the redshift distributions with only slightly larger uncertainties in the mean redshifts of ∼0.01 − 0.02 to be used in KiDS-1000 cosmological weak lensing analyses. As this includes the SOM uncertainty, clustering-z are shown to be fully competitive on KiDS-1000 data.
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Pharo, John, Yicheng Guo, Guillermo Barro Calvo, Timothy Carleton, S. M. Faber, Puragra Guhathakurta, Susan A. Kassin, et al. "The Dwarf Galaxy Population at z ∼ 0.7: A Catalog of Emission Lines and Redshifts from Deep Keck Observations." Astrophysical Journal Supplement Series 261, no. 2 (July 20, 2022): 12. http://dx.doi.org/10.3847/1538-4365/ac6cdf.
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Abstract We present a catalog of spectroscopically measured redshifts over 0 < z < 2 and emission-line fluxes for 1440 galaxies. The majority (∼65%) of the galaxies come from the HALO7D survey, with the remainder from the DEEPwinds program. This catalog includes redshifts for 646 dwarf galaxies with log ( M ⋆ / M ⊙ ) < 9.5 . Eight-hundred and ten catalog galaxies did not have previously published spectroscopic redshifts, including 454 dwarf galaxies. HALO7D used the DEIMOS spectrograph on the Keck II telescope to take very deep (up to 32 hr exposure, with a median of ∼7 hr) optical spectroscopy in the COSMOS, EGS, GOODS-North, and GOODS-South CANDELS fields, and in some areas outside CANDELS. We compare our redshift results to existing spectroscopic and photometric redshifts in these fields, finding only a 1% rate of discrepancy with other spectroscopic redshifts. We measure a small increase in median photometric redshift error (from 1.0% to 1.3%) and catastrophic outlier rate (from 3.5% to 8%) with decreasing stellar mass. We obtained successful redshift fits for 75% of massive galaxies, and demonstrate a similar 70%–75% successful redshift measurement rate in 8.5 < log ( M ⋆ / M ⊙ ) < 9.5 galaxies, suggesting similar survey sensitivity in this low-mass range. We describe the redshift, mass, and color–magnitude distributions of the catalog galaxies, finding HALO7D galaxies representative of CANDELS galaxies up to i-band magnitudes of 25. The catalogs presented will enable studies of star formation, the mass–metallicity relation, star formation–morphology relations, and other properties of the z ∼ 0.7 dwarf galaxy population.
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Lloyd-Ronning, Nicole M., Aycin Aykutalp, and Jarrett L. Johnson. "On the cosmological evolution of long gamma-ray burst properties." Monthly Notices of the Royal Astronomical Society 488, no. 4 (August 6, 2019): 5823–32. http://dx.doi.org/10.1093/mnras/stz2155.
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ABSTRACT We examine the relationship between a number of long gamma-ray burst (lGRB) properties (isotropic emitted energy, luminosity, intrinsic duration, jet opening angle) and redshift. We find that even when accounting for conservative detector flux limits, there appears to be a significant correlation between isotropic equivalent energy and redshift, suggesting cosmological evolution of the lGRB progenitor. Analysing a sub-sample of lGRBs with jet opening angle estimates, we find the beaming-corrected lGRB emitted energy does not correlate with redshift, but jet opening angle does. Additionally, we find a statistically significant anticorrelation between the intrinsic prompt duration and redshift, even when accounting for potential selection effects. We also find that, for a given redshift, isotropic energy is positively correlated with intrinsic prompt duration. None of these GRB properties appear to be correlated with galactic offset. From our selection-effect-corrected redshift distribution, we estimate a co-moving rate density for lGRBs, and compare this to the global cosmic star formation rate (SFR). We find the lGRB rate mildly exceeds the global star formation rate between a redshift of 3 and 5, and declines rapidly at redshifts above this (although we cannot constrain the lGRB rate above a redshift of about 6 due to sample incompleteness). We find the lGRB rate diverges significantly from the SFR at lower redshifts. We discuss both the correlations and lGRB rate density in terms of various lGRB progenitor models and their apparent preference for low-metallicity environments.
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Malz, Alex I., and David W. Hogg. "How to Obtain the Redshift Distribution from Probabilistic Redshift Estimates." Astrophysical Journal 928, no. 2 (March 31, 2022): 127. http://dx.doi.org/10.3847/1538-4357/ac062f.
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Abstract A reliable estimate of the redshift distribution n(z) is crucial for using weak gravitational lensing and large-scale structures of galaxy catalogs to study cosmology. Spectroscopic redshifts for the dim and numerous galaxies of next-generation weak-lensing surveys are expected to be unavailable, making photometric redshift (photo-z) probability density functions (PDFs) the next best alternative for comprehensively encapsulating the nontrivial systematics affecting photo-z point estimation. The established stacked estimator of n(z) avoids reducing photo-z PDFs to point estimates but yields a systematically biased estimate of n(z) that worsens with a decreasing signal-to-noise ratio, the very regime where photo-z PDFs are most necessary. We introduce Cosmological Hierarchical Inference with Probabilistic Photometric Redshifts (CHIPPR), a statistically rigorous probabilistic graphical model of redshift-dependent photometry that correctly propagates the redshift uncertainty information beyond the best-fit estimator of n(z) produced by traditional procedures and is provably the only self-consistent way to recover n(z) from photo-z PDFs. We present the chippr prototype code, noting that the mathematically justifiable approach incurs computational cost. The CHIPPR approach is applicable to any one-point statistic of any random variable, provided the prior probability density used to produce the posteriors is explicitly known; if the prior is implicit, as may be the case for popular photo-z techniques, then the resulting posterior PDFs cannot be used for scientific inference. We therefore recommend that the photo-z community focus on developing methodologies that enable the recovery of photo-z likelihoods with support over all redshifts, either directly or via a known prior probability density.
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Lloyd-Ronning, Nicole, Valeria U. Hurtado, Aycin Aykutalp, Jarrett Johnson, and Chiara Ceccobello. "The evolution of gamma-ray burst jet opening angle through cosmic time." Monthly Notices of the Royal Astronomical Society 494, no. 3 (April 21, 2020): 4371–81. http://dx.doi.org/10.1093/mnras/staa1057.
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ABSTRACT Jet opening angles of long gamma-ray bursts (lGRBs) appear to evolve in cosmic time, with lGRBs at higher redshifts being on average more narrowly beamed than those at lower redshifts. We examine the nature of this anticorrelation in the context of collimation by the progenitor stellar envelope. First, we show that the data indicate a strong correlation between gamma-ray luminosity and jet opening angle, and suggest this is a natural selection effect – only the most luminous GRBs are able to successfully launch jets with large opening angles. Then, by considering progenitor properties expected to evolve through cosmic time, we show that denser stars lead to more collimated jets; we argue that the apparent anticorrelation between opening angle and redshift can be accounted for if lGRB massive star progenitors at high redshifts have higher average density compared to those at lower redshifts. This may be viable for an evolving initial mass function (IMF) – under the assumption that average density scales directly with mass, this relationship is consistent with the form of the IMF mass evolution suggested in the literature. The jet angle–redshift anticorrelation may also be explained if the lGRB progenitor population is dominated by massive stars at high redshift, while lower redshift lGRBs allow for a greater diversity of progenitor systems (that may fail to collimate the jet as acutely). Overall, however, we find both the jet angle–redshift anticorrelation and jet angle–luminosity correlation are consistent with the conditions of jet launch through, and collimation by, the envelope of a massive star progenitor.
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Garilli, B. "The VVDS: a journey through space and time." Proceedings of the International Astronomical Union 2, S235 (August 2006): 404. http://dx.doi.org/10.1017/s1743921306010362.
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The VVDS Surveys aim at understanding the combined evolution of galaxies and large scale structure and have by now collected more than 35000 redshifts in four sky areas covering a total of 4.3 square degrees. They are the only surveys of this kind using a purely apparent magnitude selection, thus avoiding the intrinsic biases present in most of the high redshift color based surveys.
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Li, I. H., H. K. C. Yee, B. C. Hsieh, D. G. Gilbank, and M. D. Gladders. "The Evolution of Galaxies and Groups in Cluster Environments at 0.3 < z < 0.6." Proceedings of the International Astronomical Union 2, S235 (August 2006): 220. http://dx.doi.org/10.1017/s1743921306006260.
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We investigate the dependence of galaxy populations on environment. Our samples are selected from the follow-up of Red-Sequence Cluster Survey (RCS) catalogs using wide-field BVRz' imaging for 60 intermediate redshift (0.3 < z < 0.6) clusters. Galaxy redshifts are estimated using an empirical photometric redshift technique with a training set of 3996 galaxies to z 1.4. To obtain photometric redshift probability density for each galaxy, we bootstrap the training set galaxies to estimate the fitting uncertainties and apply Monte-Carlo method to simulate galaxy magnitudes errors. In order to find galaxy groups using photometric redshift, we develop a modified friends-of-friends algorithm, ‘Probability Friends-of-Friends Algorithm (pFOF)’, where photometric redshift redshift probability densities of individual galaxies are used to determine member galaxies of a group. We calculate the red galaxy fraction to infer the evolutionary status of cluster galaxies and also for galaxies in groups selected in the same redshift space as the clusters.
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Sonnenfeld, Alessandro. "Statistical strong lensing." Astronomy & Astrophysics 659 (March 2022): A133. http://dx.doi.org/10.1051/0004-6361/202142467.
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Context. Strong lensing mass measurements require the knowledge of the redshift of both the lens and the source galaxy. Traditionally, spectroscopic redshifts are used for this purpose. Upcoming surveys, however, will lead to the discovery of ∼105 strong lenses, and it will be very difficult to obtain spectroscopic redshifts for most of them. Photometric redshift measurements will also be very challenging due to the blending between lens and source light. Aims. The goal of this work is to demonstrate how to carry out an inference of the structural properties of the galaxy population from the analysis of a set of strong lenses with no individual source redshift measurements, and to assess the loss in precision compared to the case in which spectroscopic redshifts are available. Methods. Building on the formalism introduced in Paper III, I developed a method that allows a statistical strong lensing inference to be carried out while marginalising over the source redshifts. This method, which relies on the knowledge of the properties of the unlensed background source population and of the selection function of the survey, generalises an approach known as photogeometric redshift, originally introduced by the Strong Lensing Legacy Survey collaboration. I tested the method on simulated data consisting of a subset of 137 strong lenses that is complete above a cut in observational space. Results. The method recovers the properties of the galaxy population with a precision that is comparable to that attainable in the case in which individual source redshifts are known. Conclusions. The photogeometric redshift method is a viable approach for the analysis of large sets of strong lenses provided that the background source population properties and lens selection function are well known.
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Roychowdhury, Sambit, Clive Dickinson, and Ian W. A. Browne. "A first quantification of the effects of absorption for H I intensity mapping experiments." Astronomy & Astrophysics 631 (November 2019): A115. http://dx.doi.org/10.1051/0004-6361/201936139.
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Context. HI intensity mapping (IM) will be used to do precision cosmology, using many existing and upcoming radio observatories. It will measure the integrated HI 21 cm emission signal from “voxels” of the sky at different redshifts. The signal will be contaminated due to absorption, the largest component of which will be the flux absorbed by the HI emitting sources themselves from the potentially bright flux incident on them from background radio continuum sources. Aims. We, for the first time, provide a quantitative estimate of the magnitude of the absorbed flux compared to the emitted HI flux. The ratio of the two fluxes was calculated for various voxels placed at redshifts between 0.1 and 2.5. Methods. We used a cosmological sky simulation of the atomic HI emission line, and summed over the emitted and absorbed fluxes for all sources within voxels at different redshifts. In order to determine the absorbed flux, for each HI source the flux incident from background radio continuum sources was estimated by determining the numbers, sizes, and redshift distribution of radio continuum sources that lie behind it, based on existing observations and simulations. The amount of this incident flux that is absorbed by each HI source was calculated using a relation between integrated optical depth with HI column density determined using observations of damped Lyman-α systems (DLAs) and sub-DLAs. Results. We find that for the same co-moving volume of sky, the HI emission decreases quickly with increasing redshift, while the absorption varies much less with redshift and follows the redshift distribution of faint sources that dominate the number counts of radio continuum sources. This results in the fraction of absorption compared to emission to be negligible in the nearby Universe (up to a redshift of ∼0.5), increases to about 10% at a redshift of one, and continues to increase to about 30% up to a redshift of 2.5. These numbers can vary significantly due to the uncertainty on the exact form of the following relations: firstly, the number counts of radio continuum sources at sub-mJy flux densities; secondly, the relation between integrated optical depth and HI column density of HI sources; and thirdly, the redshift distribution of radio continuum sources up to the highest redshifts. Conclusions. Absorption of the flux incident from background radio continuum sources might become an important contaminant to HI IM signals beyond redshifts of 0.5. The impact of absorption needs to be quantified more accurately using inputs from upcoming deep surveys of radio continuum sources, H I absorption, and HI emission with the Square Kilometre Array and its precursors.
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Hemler, Z. S., Paul Torrey, Jia Qi, Lars Hernquist, Mark Vogelsberger, Xiangcheng Ma, Lisa J. Kewley, et al. "Gas-phase metallicity gradients of TNG50 star-forming galaxies." Monthly Notices of the Royal Astronomical Society 506, no. 2 (June 29, 2021): 3024–48. http://dx.doi.org/10.1093/mnras/stab1803.
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ABSTRACT We present the radial gas-phase, mass-weighted metallicity profiles and gradients of the TNG50 star-forming galaxy population measured at redshifts z = 0–3. We investigate the redshift evolution of gradients and examine relations between gradient (negative) steepness and galaxy properties. We find that TNG50 gradients are predominantly negative at all redshifts, although we observe significant diversity among these negative gradients. We determine that the gradients of all galaxies grow more negative with redshift at a roughly constant rate of approximately $-0.02\ \mathrm{dex\, kpc^{-1}}/\Delta z$. This rate does not vary significantly with galaxy mass. We observe a weak negative correlation between gradient (negative) steepness and galaxy stellar mass at z < 2. However, when we normalize gradients by a characteristic radius defined by the galactic star formation distribution, we find that these normalized gradients do not vary significantly with either stellar mass or redshift. We place our results in the context of previous simulations and show that TNG50 high-redshift gradients are more negative than those of models featuring burstier feedback, which may further highlight high-redshift gradients as important discriminators of galaxy formation models. We also find that z = 0 and z = 0.5 TNG50 gradients are consistent with the gradients observed in galaxies at these redshifts, although the preference for flat gradients observed in redshift z ≳ 1 galaxies is not present in TNG50. If future JWST (James Webb Space Telescope) and ELT (Extremely Large Telescope) observations validate these flat gradients, it may indicate a need for simulation models to implement more powerful radial gas mixing within the ISM (interstellar medium), possibly via turbulence and/or stronger winds.
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Deng, Xin-Fa. "THE ENVIRONMENTAL DEPENDENCE OF GALAXY AGE AND STELLAR MASS IN THE REDSHIFT REGION 0.6 ≤ z ≤ 0.75." Revista Mexicana de Astronomía y Astrofísica 55, no. 2 (September 13, 2019): 185–91. http://dx.doi.org/10.22201/ia.01851101p.2019.55.02.06.
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In this work, I construct a LRG (Luminous Red Galaxy) sample with redshifts 0.6 ≤ z ≤ 0.75 from the Sloan Digital Sky Survey Data Release 15 (SDSS DR15), which contains 184172 CMASS LRGs and 27158 eBOSS LRGs, and examine the environmental dependence of galaxy age and stellar mass in this galaxy sample. I divide this LRG sample into subsamples with a redshift binning size of ∆z = 0.01, and analyze the environmental dependence of galaxy age and stellar mass for these subsamples in each redshift bin. Overall, galaxy age and stellar mass in the LRG sample with redshift 0.6 ≤ z ≤ 0.75 are very weakly correlated with the local environment, which shows that minimal environmental dependence of galaxy parameters can continue to larger redshifts.
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Glowacki, M., E. Elson, and R. Davé. "The redshift evolution of the baryonic Tully–Fisher relation in SIMBA." Monthly Notices of the Royal Astronomical Society 507, no. 3 (August 6, 2021): 3267–84. http://dx.doi.org/10.1093/mnras/stab2279.
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ABSTRACT The baryonic Tully–Fisher relation (BTFR) is an important tool for constraining galaxy evolution models. As 21-cm H i emission studies have been largely restricted to low redshifts, the redshift evolution of the BTFR is less studied. The upcoming LADUMA survey (Looking At the Distant Universe with the MeerKAT Array) will address this. As preparation for LADUMA, we use the SIMBA hydrodynamical galaxy formation simulation from the SIMBA-hires $(25\, h^{-1}{\rm Mpc})^3$ run to generate rotational velocity measures from galaxy rotation curves (Vflat) and H i spectral line profile widths (W50 and W20) at three different redshifts (z = 0, 0.5, and 1). Using these measures, together with the dark matter velocity dispersion and halo mass, we consider the redshift evolution of the BTFR of SIMBA galaxies. We find that LADUMA will be successful in detecting weak redshift evolution of the BTFR, provided that auxiliary data are used to distinguish galaxies with discy morphologies. W20 spectral line widths give lower scatter and more pronounced redshift evolution compared to W50. We also compare these rotational velocity measures to the dark matter velocity dispersion across redshift and galaxy morphology. We find weak redshift evolution between rotational velocity and the dark matter halo mass, and provide fits for estimating a galaxy’s dark matter halo mass from H i spectral line widths. This study with SIMBA showcases the importance of upcoming, deep Square Kilometre Array pathfinder surveys such as LADUMA, and provides predictions to compare with the redshift evolution of the BTFR and galaxy dark matter content from H i rotational velocity measures.
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Padilla, N. D., and C. M. Baugh. "Cluster correlations in redshift space." Monthly Notices of the Royal Astronomical Society 329, no. 2 (January 2002): 431–44. http://dx.doi.org/10.1046/j.1365-8711.2002.04992.x.
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Cai, Yan-Chuan, Andy Taylor, John A. Peacock, and Nelson Padilla. "Redshift-space distortions around voids." Monthly Notices of the Royal Astronomical Society 462, no. 3 (July 28, 2016): 2465–77. http://dx.doi.org/10.1093/mnras/stw1809.
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Zhou, Rongpu, Michael C. Cooper, Jeffrey A. Newman, Matthew L. N. Ashby, James Aird, Christopher J. Conselice, Marc Davis, et al. "Deep ugrizY imaging and DEEP2/3 spectroscopy: a photometric redshift testbed for LSST and public release of data from the DEEP3 Galaxy Redshift Survey." Monthly Notices of the Royal Astronomical Society 488, no. 4 (July 25, 2019): 4565–84. http://dx.doi.org/10.1093/mnras/stz1866.
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ABSTRACT We present catalogues of calibrated photometry and spectroscopic redshifts in the Extended Groth Strip, intended for studies of photometric redshifts (photo-z’s). The data includes ugriz photometry from Canada–France–Hawaii Telescope Legacy Survey (CFHTLS) and Y-band photometry from the Subaru Suprime camera, as well as spectroscopic redshifts from the DEEP2, DEEP3, and 3D-HST surveys. These catalogues incorporate corrections to produce effectively matched-aperture photometry across all bands, based upon object size information available in the catalogue and Moffat profile point spread function fits. We test this catalogue with a simple machine learning-based photometric redshift algorithm based upon Random Forest regression, and find that the corrected aperture photometry leads to significant improvement in photo-z accuracy compared to the original SExtractor catalogues from CFHTLS and Subaru. The deep ugrizY photometry and spectroscopic redshifts are well suited for empirical tests of photometric redshift algorithms for LSST. The resulting catalogues are publicly available at http://d-scholarship.pitt.edu/36064/. We include a basic summary of the strategy of the DEEP3 Galaxy Redshift Survey to accompany the recent public release of DEEP3 data.
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García-Farieta, Jorge Enrique, Federico Marulli, Lauro Moscardini, Alfonso Veropalumbo, and Rigoberto A. Casas-Miranda. "Validating the methodology for constraining the linear growth rate from clustering anisotropies." Monthly Notices of the Royal Astronomical Society 494, no. 2 (March 20, 2020): 1658–74. http://dx.doi.org/10.1093/mnras/staa791.
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ABSTRACT Redshift-space clustering distortions provide one of the most powerful probes to test the gravity theory on the largest cosmological scales. We perform a systematic validation study of the state-of-the-art statistical methods currently used to constrain the linear growth rate from redshift-space distortions in the galaxy two-point correlation function. The numerical pipelines are tested on mock halo catalogues extracted from large N-body simulations of the standard cosmological framework. We consider both the monopole and quadrupole multipole moments of the redshift-space two-point correlation function, as well as the radial and transverse clustering wedges, in the comoving scale range 10 < r[$h^{-1}\, \mbox{Mpc}$] < 55. Moreover, we investigate the impact of redshift measurement errors on the growth rate and linear bias measurements due to the assumptions in the redshift-space distortion model. Considering both the dispersion model and two widely used models based on perturbation theory, we find that the linear growth rate is underestimated by about $5\!-\! 10\, {\rm {per\ cent}}$ at $z$ < 1, while limiting the analysis at larger scales, r > 30 $h^{-1}\, \mbox{Mpc}$, the discrepancy is reduced below $5\, {\rm {per\ cent}}$. At higher redshifts, we find instead an overall good agreement between measurements and model predictions. Though this accuracy is good enough for clustering analyses in current redshift surveys, the models have to be further improved not to introduce significant systematics in RSD constraints from next-generation galaxy surveys. The effect of redshift errors is degenerate with the one of small-scale random motions, and can be marginalized over in the statistical analysis, not introducing any statistically significant bias in the linear growth constraints, especially at $z$ ≥ 1.
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Pandya, Viraj, Joel Primack, Peter Behroozi, Avishai Dekel, Haowen Zhang, Elliot Eckholm, Sandra M. Faber, et al. "Can intrinsic alignments of elongated low-mass galaxies be used to map the cosmic web at high redshift?" Monthly Notices of the Royal Astronomical Society 488, no. 4 (August 2, 2019): 5580–93. http://dx.doi.org/10.1093/mnras/stz2129.
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ABSTRACT Hubble Space Telescope observations show that low-mass ($M_*=10^9\!-\!10^{10}\, \mathrm{M}_{\odot }$) galaxies at high redshift (z = 1.0–2.5) tend to be elongated (prolate) rather than disky (oblate) or spheroidal. This is explained in zoom-in cosmological hydrodynamical simulations by the fact that these galaxies are forming in cosmic web filaments where accretion happens preferentially along the direction of elongation. We ask whether the elongated morphology of these galaxies allows them to be used as effective tracers of cosmic web filaments at high redshift via their intrinsic alignments. Using mock light cones and spectroscopically confirmed galaxy pairs from the Cosmic Assembly Near-infared Deep Extragalactic Legacy Survey (CANDELS), we test two types of alignments: (1) between the galaxy major axis and the direction to nearby galaxies of any mass and (2) between the major axes of nearby pairs of low-mass, likely prolate, galaxies. The mock light cones predict strong signals in 3D real space, 3D redshift space, and 2D projected redshift space for both types of alignments (assuming prolate galaxy orientations are the same as those of their host prolate haloes), but we do not detect significant alignment signals in CANDELS observations. However, we show that spectroscopic redshifts have been obtained for only a small fraction of highly elongated galaxies, and accounting for spectroscopic incompleteness and redshift errors significantly degrades the 2D mock signal. This may partly explain the alignment discrepancy and highlights one of several avenues for future work.
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Koo, D. C. "A Glimpse of Field Galaxies at Redshifts z ∼ 1 using HST and the Keck Telescope." Symposium - International Astronomical Union 171 (1996): 217–20. http://dx.doi.org/10.1017/s0074180900232385.
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Data from the Keck and Hubble Space Telescopes have been combined to explore the nature of very faint I > 22 field galaxies. At a redshift z ∼ 1, such galaxies have luminosities similar to that of typical galaxies today. Though small, our sample of 33 redshifts already suggest that the median redshift for I > 22 galaxies is higher than the z = 0.6 expected for the “maximum merger model” of Carlberg (1995). At redshifts z > 0.8, mergers, interactions, and infall of minor galaxies into larger hosts appear to be common events; a wide diversity of morphological types existed; and some stellar populations were already so red that their major formation epoch occurred at redshifts z > 2.
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Myles, J., A. Alarcon, A. Amon, C. Sánchez, S. Everett, J. DeRose, J. McCullough, et al. "Dark Energy Survey Year 3 results: redshift calibration of the weak lensing source galaxies." Monthly Notices of the Royal Astronomical Society 505, no. 3 (May 27, 2021): 4249–77. http://dx.doi.org/10.1093/mnras/stab1515.
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ABSTRACT Determining the distribution of redshifts of galaxies observed by wide-field photometric experiments like the Dark Energy Survey (DES) is an essential component to mapping the matter density field with gravitational lensing. In this work we describe the methods used to assign individual weak lensing source galaxies from the DES Year 3 Weak Lensing Source Catalogue to four tomographic bins and to estimate the redshift distributions in these bins. As the first application of these methods to data, we validate that the assumptions made apply to the DES Y3 weak lensing source galaxies and develop a full treatment of systematic uncertainties. Our method consists of combining information from three independent likelihood functions: self-organizing map p(z) (sompz), a method for constraining redshifts from galaxy photometry; clustering redshifts (WZ), constraints on redshifts from cross-correlations of galaxy density functions; and shear ratios (SRs), which provide constraints on redshifts from the ratios of the galaxy-shear correlation functions at small scales. Finally, we describe how these independent probes are combined to yield an ensemble of redshift distributions encapsulating our full uncertainty. We calibrate redshifts with combined effective uncertainties of σ〈z〉 ∼ 0.01 on the mean redshift in each tomographic bin.
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Fisher, K. B., and A. Nusser. "The non-linear redshift-space power spectrum: from redshift surveys." Monthly Notices of the Royal Astronomical Society 279, no. 1 (March 1, 1996): L1—L5. http://dx.doi.org/10.1093/mnras/279.1.l1.
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Cai, Yan-Chuan, Nick Kaiser, Shaun Cole, and Carlos Frenk. "Gravitational redshift and asymmetric redshift-space distortions for stacked clusters." Monthly Notices of the Royal Astronomical Society 468, no. 2 (February 23, 2017): 1981–93. http://dx.doi.org/10.1093/mnras/stx469.
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Saxena, A., R. S. Ellis, P. U. Förster, A. Calabrò, L. Pentericci, A. C. Carnall, M. Castellano, et al. "The VANDELS Survey: new constraints on the high-mass X-ray binary populations in normal star-forming galaxies at 3 < z < 5.5." Monthly Notices of the Royal Astronomical Society 505, no. 4 (May 31, 2021): 4798–812. http://dx.doi.org/10.1093/mnras/stab1575.
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ABSTRACT We use VANDELS spectroscopic data overlapping with the ≃7 Ms Chandra Deep Field South survey to extend studies of high-mass X-ray binary systems (HMXBs) in 301 normal star-forming galaxies in the redshift range 3 < z < 5.5. Our analysis evaluates correlations between X-ray luminosities (LX), star formation rates (SFRs), and stellar metallicities (Z⋆) to higher redshifts and over a wider range in galaxy properties than hitherto. Using a stacking analysis performed in bins of both redshift and SFR for sources with robust spectroscopic redshifts without AGN signatures, we find convincing evolutionary trends in the ratio LX/SFR to the highest redshifts probed, with a stronger trend for galaxies with lower SFRs. Combining our data with published samples at lower redshift, the evolution of LX/SFR to z ≃ 5 proceeds as (1 + z)1.03 ± 0.02. Using stellar metallicities derived from photospheric absorption features in our spectroscopic data, we confirm indications at lower redshifts that LX/SFR is stronger for metal-poor galaxies. We use semi-analytic models to show that metallicity dependence of LX/SFR alone may not be sufficient to fully explain the observed redshift evolution of X-ray emission from HMXBs, particularly for galaxies with SFR < 30 M⊙ yr−1. We speculate that reduced overall stellar ages and ‘burstier’ star formation histories in the early Universe may lead to higher LX/SFR for the same metallicity. We then define the redshift-dependent contribution of HMXBs to the integrated X-ray luminosity density and, in comparison with models, find that the contribution of HMXBs to the cosmic X-ray background at z > 6 may be ≳0.25 dex higher than previously estimated.
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Gogarten, Stephanie M., Julianne J. Dalcanton, Luc Simard, Gregory Rudnick, and Vandana Desai. "The Size-Luminosity Relation of Disk Galaxies in EDisCS Clusters." Proceedings of the International Astronomical Union 2, S235 (August 2006): 201. http://dx.doi.org/10.1017/s1743921306006077.
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AbstractWe present the size-luminosity relation (SLR) for disk galaxies observed in eight clusters from the ESO Distant Cluster Survey (EDisCS). These clusters, at redshifts 0.4 < z < 0.8, were observed with the Hubble Space Telescope's Advanced Camera for Surveys. While we observe a change in the SLR with redshift, namely that there is an absence of low surface brightness galaxies at high redshift, we demonstrate that this could be a product of selection effects and thus is not a confirmation of evolution. We also compare the SLR for cluster and field galaxies in each redshift bin and see no significant effects of environment on the SLR.
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Stylianou, Natalia, Alex I. Malz, Peter Hatfield, John Franklin Crenshaw, and Julia Gschwend. "The Sensitivity of GPz Estimates of Photo-z Posterior PDFs to Realistically Complex Training Set Imperfections." Publications of the Astronomical Society of the Pacific 134, no. 1034 (April 1, 2022): 044501. http://dx.doi.org/10.1088/1538-3873/ac59bf.
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Abstract The accurate estimation of photometric redshifts is crucial to many upcoming galaxy surveys, for example, the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST). Almost all Rubin extragalactic and cosmological science requires accurate and precise calculation of photometric redshifts; many diverse approaches to this problem are currently in the process of being developed, validated, and tested. In this work, we use the photometric redshift code GPz to examine two realistically complex training set imperfections scenarios for machine learning based photometric redshift calculation: (i) where the spectroscopic training set has a very different distribution in color–magnitude space to the test set, and (ii) where the effect of emission line confusion causes a fraction of the training spectroscopic sample to not have the true redshift. By evaluating the sensitivity of GPz to a range of increasingly severe imperfections, with a range of metrics (both of photo-z point estimates as well as posterior probability distribution functions, PDFs), we quantify the degree to which predictions get worse with higher degrees of degradation. In particular, we find that there is a substantial drop-off in photo-z quality when line-confusion goes above ∼1%, and sample incompleteness below a redshift of 1.5, for an experimental setup using data from the Buzzard Flock synthetic sky catalogs.
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Stylianou, Natalia, Alex I. Malz, Peter Hatfield, John Franklin Crenshaw, and Julia Gschwend. "The Sensitivity of GPz Estimates of Photo-z Posterior PDFs to Realistically Complex Training Set Imperfections." Publications of the Astronomical Society of the Pacific 134, no. 1034 (April 1, 2022): 044501. http://dx.doi.org/10.1088/1538-3873/ac59bf.
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Abstract The accurate estimation of photometric redshifts is crucial to many upcoming galaxy surveys, for example, the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST). Almost all Rubin extragalactic and cosmological science requires accurate and precise calculation of photometric redshifts; many diverse approaches to this problem are currently in the process of being developed, validated, and tested. In this work, we use the photometric redshift code GPz to examine two realistically complex training set imperfections scenarios for machine learning based photometric redshift calculation: (i) where the spectroscopic training set has a very different distribution in color–magnitude space to the test set, and (ii) where the effect of emission line confusion causes a fraction of the training spectroscopic sample to not have the true redshift. By evaluating the sensitivity of GPz to a range of increasingly severe imperfections, with a range of metrics (both of photo-z point estimates as well as posterior probability distribution functions, PDFs), we quantify the degree to which predictions get worse with higher degrees of degradation. In particular, we find that there is a substantial drop-off in photo-z quality when line-confusion goes above ∼1%, and sample incompleteness below a redshift of 1.5, for an experimental setup using data from the Buzzard Flock synthetic sky catalogs.
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Hasan, Imran S., Samuel J. Schmidt, Michael D. Schneider, and J. Anthony Tyson. "The impact of tomographic redshift bin width errors on cosmological probes." Monthly Notices of the Royal Astronomical Society 511, no. 1 (January 3, 2022): 1029–42. http://dx.doi.org/10.1093/mnras/stab3798.
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ABSTRACT Systematic errors in the galaxy redshift distribution n(z) can propagate to systematic errors in the derived cosmology. We characterize how the degenerate effects in tomographic bin widths and galaxy bias impart systematic errors on cosmology inference using observational data from the Deep Lens Survey. For this we use a combination of galaxy clustering and galaxy–galaxy lensing. We present two end-to-end analyses from the catalogue level to parameter estimation. We produce an initial cosmological inference using fiducial tomographic redshift bins derived from photometric redshifts, then compare this with a result where the redshift bins are empirically corrected using a set of spectroscopic redshifts. We find that the derived parameter S8 ≡ σ8(Ωm/.3)1/2 decreases from $0.841^{+0.062}_{-0.061}$ to $0.781^{0.061}_{0.054}$ upon correcting the n(z) errors in the second method.
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Weaver, J. R., O. B. Kauffmann, O. Ilbert, H. J. McCracken, A. Moneti, S. Toft, G. Brammer, et al. "COSMOS2020: A Panchromatic View of the Universe to z ∼ 10 from Two Complementary Catalogs." Astrophysical Journal Supplement Series 258, no. 1 (January 1, 2022): 11. http://dx.doi.org/10.3847/1538-4365/ac3078.
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Abstract The Cosmic Evolution Survey (COSMOS) has become a cornerstone of extragalactic astronomy. Since the last public catalog in 2015, a wealth of new imaging and spectroscopic data have been collected in the COSMOS field. This paper describes the collection, processing, and analysis of these new imaging data to produce a new reference photometric redshift catalog. Source detection and multiwavelength photometry are performed for 1.7 million sources across the 2 deg2 of the COSMOS field, ∼966,000 of which are measured with all available broadband data using both traditional aperture photometric methods and a new profile-fitting photometric extraction tool, The Farmer, which we have developed. A detailed comparison of the two resulting photometric catalogs is presented. Photometric redshifts are computed for all sources in each catalog utilizing two independent photometric redshift codes. Finally, a comparison is made between the performance of the photometric methodologies and of the redshift codes to demonstrate an exceptional degree of self-consistency in the resulting photometric redshifts. The i < 21 sources have subpercent photometric redshift accuracy and even the faintest sources at 25 < i < 27 reach a precision of 5%. Finally, these results are discussed in the context of previous, current, and future surveys in the COSMOS field. Compared to COSMOS2015, it reaches the same photometric redshift precision at almost one magnitude deeper. Both photometric catalogs and their photometric redshift solutions and physical parameters will be made available through the usual astronomical archive systems (ESO Phase 3, IPAC-IRSA, and CDS).
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Curran, S. J., and J. P. Moss. "Quasi-stellar object redshift estimates from optical, near-infrared, and ultraviolet colours." Astronomy & Astrophysics 629 (September 2019): A56. http://dx.doi.org/10.1051/0004-6361/201936179.
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A simple estimate of the photometric redshift would prove invaluable to forthcoming continuum surveys on the next generation of large radio telescopes, as well as mitigating the existing bias towards the most optically bright sources. While there is a well-known correlation between the near-infrared K-band magnitude and redshift for galaxies, we find the K − z relation to break down for samples dominated by quasi-stellar objects. We hypothesise that this is due to the additional contribution to the near-infrared flux by the active galactic nucleus, and, as such, the K-band magnitude can only provide a lower limit to the redshift in the case of active galactic nuclei, which will dominate the radio surveys. From a large optical dataset, we find a tight relationship between the rest-frame (U − K)/(W2 − FUV) colour ratio and spectroscopic redshift over a sample of 17 000 sources, spanning z ≈ 0.1−5. Using the observed-frame ratios of (U − K)/(W2 − FUV) for redshifts of z ≲ 1, (I − W2)/(W3 − U) for 1 ≲ z ≲ 3, and (I − W2.5)/(W4 − R) for z ≳ 3, where W2.5 is the λ = 8.0 μm magnitude and the appropriate redshift ranges are estimated from the W2 (4.5 μm) magnitude, we find this to be a robust photometric redshift estimator for quasars. We suggest that the rest-frame U − K colour traces the excess flux from the AGN over this wide range of redshifts, although the W2 − FUV colour is required to break the degeneracy.
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Hwang, Ho Seong, Jihye Shin, and Hyunmi Song. "Evolution of star formation rate–density relation over cosmic time in a simulated universe: the observed reversal reproduced." Monthly Notices of the Royal Astronomical Society 489, no. 1 (August 5, 2019): 339–48. http://dx.doi.org/10.1093/mnras/stz2136.
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ABSTRACT We use the IllustrisTNG cosmological hydrodynamical simulation to study the evolution of star formation rate (SFR)–density relation over cosmic time. We construct several samples of galaxies at different redshifts from z = 2.0 to z = 0.0, which have the same comoving number density. The SFR of galaxies decreases with local density at z = 0.0, but its dependence on local density becomes weaker with redshift. At z ≳ 1.0, the SFR of galaxies increases with local density (reversal of the SFR–density relation), and its dependence becomes stronger with redshift. This change of SFR–density relation with redshift still remains even when fixing the stellar masses of galaxies. The dependence of SFR on the distance to a galaxy cluster also shows a change with redshift in a way similar to the case based on local density, but the reversal happens at a higher redshift, z ∼ 1.5, in clusters. On the other hand, the molecular gas fraction always decreases with local density regardless of redshift at z = 0.0–2.0 even though the dependence becomes weaker when we fix the stellar mass. Our study demonstrates that the observed reversal of the SFR–density relation at z ≳ 1.0 can be successfully reproduced in cosmological simulations. Our results are consistent with the idea that massive, star-forming galaxies are strongly clustered at high redshifts, forming larger structures. These galaxies then consume their gas faster than those in low-density regions through frequent interactions with other galaxies, ending up being quiescent in the local universe.
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Saito, Shun, Sylvain de la Torre, Olivier Ilbert, Cédric Dubois, Kiyoto Yabe, and Jean Coupon. "The synthetic Emission Line COSMOS catalogue: Hα and [O ii] galaxy luminosity functions and counts at 0.3 < z < 2.5." Monthly Notices of the Royal Astronomical Society 494, no. 1 (March 14, 2020): 199–217. http://dx.doi.org/10.1093/mnras/staa727.
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ABSTRACT Star-forming galaxies with strong nebular and collisional emission lines are privileged target galaxies in forthcoming cosmological large galaxy redshift surveys. We use the COSMOS2015 photometric catalogue to model galaxy spectral energy distributions and emission-line fluxes. We adopt an empirical but physically motivated model that uses information from the best-fitting spectral energy distribution of stellar continuum to each galaxy. The emission-line flux model is calibrated and validated against direct flux measurements in subsets of galaxies that have 3D-HST or zCOSMOS-Bright spectra. We take a particular care in modelling dust attenuation such that our model can explain both Hα and [O ii] observed fluxes at different redshifts. We find that a simple solution to this is to introduce a redshift evolution in the dust attenuation fraction parameter, f = Estar(B − V)/Egas(B − V), as f(z) = 0.44 + 0.2z. From this catalogue, we derive the Hα and [O ii] luminosity functions up to redshifts of about 2.5 after carefully accounting for emission line flux and redshift errors. This allows us to make predictions for Hα and [O ii] galaxy number counts in next-generation cosmological redshift surveys. Our modelled emission lines and spectra in the COSMOS2015 catalogue shall be useful to study the target selection for planned next-generation galaxy redshift surveys and we make them publicly available as ‘EL-COSMOS’ on the ASPIC data base.