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1
Skillman, Evan D. "Dwarf Galaxies as Low Surface Brightness Galaxies." International Astronomical Union Colloquium 171 (1999): 169–76. http://dx.doi.org/10.1017/s0252921100054270.
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AbstractBecause of the weak correlation between surface brightness and luminosity, as galaxy surveys reach to lower surface brightnesses, increasing numbers of dwarf galaxies are found. Thus, studies of dwarf galaxies are relevant to our understanding of the low surface brightness universe. In particular, studies of nearby LSB dwarfs may help to answer questions concerning: (1) star formation in low abundance and low mass surface density envrionments, (2) star formation histories of galaxies and the relative youth of LSB galaxies, and (3) the chemical evolution of LSB galaxies. HST WFPC2 photometry of the resolved stars in nearby dwarf galaxies is particularly useful for all three questions.H II region abundances remain the best probe of current ISM abundances. Current evidence favors total mass (or luminosity) as the primary factor for determining the present day chemical abundance in both LSB and HSB galaxies. It remains possible that mass surface density (or surface brightness) may be a second controlling parameter.
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Dutil, Yvan, and Jean-René Roy. "Evidence for a Morphological Evolution of Spiral Galaxies." Symposium - International Astronomical Union 204 (2001): 387. http://dx.doi.org/10.1017/s0074180900226302.
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A detailed analysis of the oxygen abundance profile has been carried out on a sample of spiral galaxies from which very good data was available. The early-type galaxies of our sample display gradients that are flatter, and overall levels of O/H abundances that are higher, than those of normal late-type galaxies. Early-type galaxies show an identical trend in the behavior of extrapolated central abundance versus morphological type to that shown by late-type galaxies with strong bars, even in the absence of a bar. On a diagram showing extrapolated central abundances versus morphological types, two clearly separated sequences appear: late-type barred galaxies and early-type (barred or unbarred) galaxies clearly fall on a sequence 0.5 dex in abundance below that of normal late-type galaxies. This behavior is consistent with theoretical models of morphological evolution of disk galaxies by the formation and dissolution of a bar over a period of a few 109 yr, where later type galaxies (Sd, Sc, SBc) evolve into earlier-type disk galaxies (Sb, Sa) through transitory SBc and SBb phases.
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Klypin, Anatoly, Igor Karachentsev, Dmitry Makarov, and Olga Nasonova. "Abundance of field galaxies." Monthly Notices of the Royal Astronomical Society 454, no. 2 (October 7, 2015): 1798–810. http://dx.doi.org/10.1093/mnras/stv2040.
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Boardman, N. F., G. Zasowski, J. A. Newman, S. F. Sanchez, A. Schaefer, J. Lian, D. Bizyaev, and N. Drory. "SDSS-IV MaNGA: galaxy gas-phase metallicity gradients vary across the mass–size plane." Monthly Notices of the Royal Astronomical Society 501, no. 1 (December 8, 2020): 948–53. http://dx.doi.org/10.1093/mnras/staa3785.
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ABSTRACT Gas-phase abundances and abundance gradients provide much information on past stellar generations, and are powerful probes of how galaxies evolve. Gas abundance gradients in galaxies have been studied as functions of galaxies’ mass and size individually, but have largely not been considered across the galaxy mass–size plane. Thus, we investigate gas-phase abundance gradients across this plane, using a sample of over 1000 galaxies selected from the MApping Nearby Galaxies at APO (MaNGA) spectroscopic survey. We find that gradients vary systematically such that above 1010 M⊙, smaller galaxies display flatter gradients than larger galaxies at a given stellar mass. This mass–size behaviour cannot be explained by instrumental effects, nor is it simply a reflection of known trends between gradients and morphology. We explore multiple possibilities for a physical origin for this pattern, though further work is needed to establish a firm physical interpretation.
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Pilyugin, L. S., E. K. Grebel, I. A. Zinchenko, Y. A. Nefedyev, and J. M. Vílchez. "Relations between abundance characteristics and rotation velocity for star-forming MaNGA galaxies." Astronomy & Astrophysics 623 (March 2019): A122. http://dx.doi.org/10.1051/0004-6361/201834239.
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We derive rotation curves, surface brightness profiles, and oxygen abundance distributions for 147 late-type galaxies using the publicly available spectroscopy obtained by the MaNGA survey. Changes of the central oxygen abundance (O/H)0, the abundance at the optical radius (O/H)R25, and the abundance gradient with rotation velocity Vrot were examined for galaxies with rotation velocities from 90 km s−1 to 350 km s−1. We find that each relation shows a break at Vrot∗ ∼ 200 km s−1. The central (O/H)0 abundance increases with rising Vrot and the slope of the (O/H)0–Vrot relation is steeper for galaxies with Vrot ≲ Vrot∗. The mean scatter of the central abundances around this relation is 0.053 dex. The relation between the abundance at the optical radius of a galaxy and its rotation velocity is similar; the mean scatter in abundances around this relation is 0.081 dex. The radial abundance gradient expressed in dex/kpc flattens with the increase of the rotation velocity. The slope of the relation is very low for galaxies with Vrot ≳ Vrot∗. The abundance gradient expressed in dex/R25 is roughly constant for galaxies with Vrot ≲ Vrot∗, flattens towards Vrot∗, and then again is roughly constant for galaxies with Vrot ≳ Vrot∗. The change of the gradient expressed in terms of dex/hd (where hd is the disc scale length), in terms of dex/Re, d (where Re, d is the disc effective radius), and in terms of dex/Re, g (where Re, g is the galaxy effective radius) with rotation velocity is similar to that for gradient in dex/R25. The relations between abundance characteristics and other basic parameters (stellar mass, luminosity, and radius) are also considered.
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Flury, Sophia R., and Edward C. Moran. "Chemical abundances in active galaxies." Monthly Notices of the Royal Astronomical Society 496, no. 2 (June 6, 2020): 2191–203. http://dx.doi.org/10.1093/mnras/staa1563.
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ABSTRACT The Sloan Digital Sky Survey (SDSS) has proved to be a powerful resource for understanding the physical properties and chemical composition of star-forming galaxies in the local Universe. The SDSS population of active galactic nuclei (AGNs) remains as of yet less explored in this capacity. To extend the rigorous study of H ii regions in the SDSS to AGNs, we adapt methods for computing direct-method chemical abundances for application to the narrow-line regions (NLR) of AGNs. By accounting for triply ionized oxygen, we are able to more completely estimate the total oxygen abundance. We find a strong correlation between electron temperature and oxygen abundance due to collisional cooling by metals. Furthermore, we find that nitrogen and oxygen abundances in AGNs are strongly correlated. From the metal–temperature relation and the coupling of nitrogen and oxygen abundances, we develop a new, empirically and physically motivated method for determining chemical abundances from the strong emission lines commonly employed in flux-ratio diagnostic diagrams (BPT diagrams). Our approach, which for AGNs reduces to a single equation based on the BPT line ratios, consistently recovers direct-method abundances over a 1.5 dex range in oxygen abundance with an rms uncertainty of 0.18 dex. We have determined metallicities for thousands of AGNs in the SDSS, and in the process have discovered an ionization-related discriminator for Seyfert and LINER galaxies.
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Feldmeier-Krause, A., I. Lonoce, and W. L. Freedman. "Stellar Population and Elemental Abundance Gradients of Early-type Galaxies*." Astrophysical Journal 923, no. 1 (December 1, 2021): 65. http://dx.doi.org/10.3847/1538-4357/ac281e.
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Abstract The evolution of galaxies is imprinted on their stellar populations. Several stellar population properties in massive early-type galaxies have been shown to correlate with intrinsic galaxy properties such as the galaxy’s central velocity dispersion, suggesting that stars formed in an initial collapse of gas (z ∼ 2). However, stellar populations change as a function of galaxy radius, and it is not clear how local gradients of individual galaxies are influenced by global galaxy properties and galaxy environment. In this paper, we study the stellar populations of eight early-type galaxies as a function of radius. We use optical spectroscopy (∼4000–8600 Å) and full spectral fitting to measure stellar population age, metallicity, slope of the initial mass function (IMF), and nine elemental abundances (O, Mg, Si, Ca, Ti, C, N, Na, and Fe) out to 1 R e for each galaxy individually. We find a wide range of properties, with ages ranging from 3–13 Gyr. Some galaxies have a radially constant, Salpeter-like IMF, and other galaxies have a super-Salpeter IMF in the center, decreasing to a sub-Salpeter IMF at ∼0.5 R e . We find a global correlation of the central [Z/H] with the central IMF and the radial gradient of the IMF for the eight galaxies, but local correlations of the IMF slope with other stellar population parameters hold only for subsets of the galaxies in our sample. Some elemental abundances also correlate locally with each other within a galaxy, suggesting a common production channel. These local correlations appear only in subsets of our galaxies, indicating variations of the stellar content among different galaxies.
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Dors, Oli L. "Chemical abundances in Seyfert galaxies – VI. Empirical abundance calibration." Monthly Notices of the Royal Astronomical Society 507, no. 1 (July 30, 2021): 466–74. http://dx.doi.org/10.1093/mnras/stab2166.
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ABSTRACT We derived a bi-dimensional calibration between the emission-line ratios $R_{23}= ([\mathrm{ O}\, {\small {\rm II}}]\,\lambda 3726 +\lambda 3729 +[\mathrm{ O}\mathrm{ }\, {\small {\rm III}}]\,\lambda 4959 + \lambda 5007)/\rm H\,\beta$, ${\it P}=[([\mathrm{ O}\, {\small {\rm III}}]\,\lambda 4959+\lambda 5007)/{\rm H}\,\beta ]/R_{23}$ and the oxygen abundance relative to hydrogen (O/H) in the gas phase of Seyfert 1 and 2 nuclei. In view of this, emission-line intensity ratios for a sample of objects taken from the Sloan Digital Sky Survey Data Release 7 measured by the MPA/JHU group and direct estimates of O/H based on Te-method, adapted for active galactic nuclei (AGNs), are considered. We find no variation of R23 observed along the radii of AGNs, which shows that this line ratio is a good oxygen abundance (O/H) indicator for the class of objects considered in this work. The derived O/H = f(R23, P) relation produces O/H values similar to estimations via Te-method in a wide range of metallicities [$\rm 8.0 \: \lesssim \: 12+\log \,(O/H) \: \lesssim \: 9.2$]. Conversely to star-forming regions in the high-metallicity regime, R23 shows a positive correlation trend with O/H in AGNs. This indicates that the hardness of ionizing radiation is not affected by the metallicities in these objects or narrow-line regions are not significantly modified by changes in the spectral energy distribution due to metallicity variations.
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Kovtyukh, V., B. Lemasle, G. Bono, I. A. Usenko, R. da Silva, A. Kniazev, E. K. Grebel, I. L. Andronov, L. Shakun, and L. Chinarova. "The MAGIC project – III. Radial and azimuthal Galactic abundance gradients using classical Cepheids." Monthly Notices of the Royal Astronomical Society 510, no. 2 (December 4, 2021): 1894–901. http://dx.doi.org/10.1093/mnras/stab3530.
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ABSTRACT Radial abundance gradients provide sound constraints for chemo-dynamical models of galaxies. Azimuthal variations of abundance ratios are solid diagnostics to understand their chemical enrichment. In this paper, we investigate azimuthal variations of abundances in the Milky Way using Cepheids. We provide the detailed chemical composition (25 elements) of 105 Classical Cepheids from high-resolution SALT spectra observed by the MAGIC project. Negative abundance gradients, with abundances decreasing from the inner to the outer disc, have been reported both in the Milky Way and in external galaxies, and our results are in full agreement with literature results. We find azimuthal variations of the oxygen abundance [O/H]. While a large number of external spirals show negligible azimuthal variations, the Milky Way seems to be one of the few galaxies with noticeable [O/H] azimuthal asymmetries. They reach ≈0.2 dex in the inner Galaxy and in the outer disc, where they are the largest, thus supporting similar findings for nearby spiral galaxies, as well as recent 2D chemo-dynamical models.
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Sen, Seyda, Reynier F. Peletier, Elisa Toloba, and Jaco J. Mentz. "Abundance Ratios in Dwarf Elliptical Galaxies." Proceedings of the International Astronomical Union 11, S321 (March 2016): 269. http://dx.doi.org/10.1017/s1743921316012503.
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AbstractThe aim of this study is to determine abundance ratios and star formation histories (SFH) of dwarf ellipticals in the nearby Virgo cluster. We perform a stellar population analysis of 39 dEs and study them using index-index and scaling relations. We find an unusual behaviour where [Na/Fe] is under-abundant w.r.t. solar while [Ca/Fe] is over-abundant.
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Stasińska, Grażyna. "Ionized gas in dwarf galaxies: Abundance indicators." Proceedings of the International Astronomical Union 4, S255 (June 2008): 375–80. http://dx.doi.org/10.1017/s1743921308025106.
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AbstractWe discuss the four basic methods to derive HII region abundances in metal-poor galaxies by presenting a few recent results obtained with these methods. We end up by commenting on the yet unsolved problem of temperature fluctuations in HII regions, which may plague abundance determinations, as well as the discrepancy between abundances derived from recombination lines and collisionally excited lines, to which inhomogeneous chemical composition might be the explanation.
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Zurita, A., E. Florido, F. Bresolin, I. Pérez, and E. Pérez-Montero. "Bar effect on gas-phase abundance gradients – II. Luminosity-dependent flattening." Monthly Notices of the Royal Astronomical Society 500, no. 2 (July 29, 2020): 2380–400. http://dx.doi.org/10.1093/mnras/staa2208.
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ABSTRACT We present here the second part of a project that aims at solving the controversy regarding the issue of the bar effect on the radial distribution of metals in the gas-phase of spiral galaxies. In Paper I, we presented a compilation of more than 2800 H ii regions belonging to 51 nearby galaxies for which we derived chemical abundances and radial abundance profiles from a homogeneous methodology. In this paper, we analyse the derived gas-phase radial abundance profiles of 12+log (O/H) and log (N/O), for barred and unbarred galaxies separately, and find that the differences in slope between barred and unbarred galaxies depend on galaxy luminosity. This is due to a different dependence of the abundance gradients (in dex kpc−1) on luminosity for the two types of galaxies: in the galaxy sample under consideration the gradients appear to be considerably shallower for strongly barred galaxies in the whole luminosity range, while profile slopes for unbarred galaxies become steeper with decreasing luminosity. Therefore, we only detect differences in slope for the lower luminosity (lower mass) galaxies (MB ≳ −19.5 or M* ≲ 1010.4 M⊙). We discuss the results in terms of the disc evolution and radial mixing induced by bars and spiral arms. Our results reconcile previous discrepant findings that were biased by the luminosity (mass) distribution of the sample galaxies and possibly by the abundance diagnostics employed.
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Maliuk, A., and I. Zinchenko. "Metallicity calibrations and oxygen abundance evolution in massive galaxies." Advances in Astronomy and Space Physics 8, no. 1 (2018): 24–27. http://dx.doi.org/10.17721/2227-1481.8.24-27.
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We determined oxygen abundances for the sample of SDSS galaxies with high masses using R3D, S3D, R2D, S2D, N and O3N2 calibrations. We investigated redshift–metallicity relation for oxygen abundances obtained by each calibration. We found that for galaxies with high stellar masses oxygen abundance obtained using all calibrations is increasing on the time interval from z = 0.5 to z = 0. However, the values of oxygen abundance enrichment rate significantly depend on adopted calibration and ranges from ~0.1 dex per unit redshift for R calibration to ~0.5 dex per unit redshift for O3N2 calibration.
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Matsushita, K., T. Ohashi, and K. Makishima. "Solving the Mysteries in Hot ISM in Early-Type Galaxies." Symposium - International Astronomical Union 188 (1998): 283. http://dx.doi.org/10.1017/s0074180900115141.
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We have analyzed ASCA data of about 30 early type galaxies, and studied their X-ray emitting ISM (InterStellar Medium) properties. Our study has been motivated by the apparently very low metallicity of the ISM, which cannot easily be reconciled with theoretical predictions. By carefully examining the abundance ratios and uncertainties in the Fe-L complex, we have concluded that the ISM abundances in X-ray luminous galaxies are in fact about 1 solar. Therefore, the severe discrepancy between the ISM and stellar abundance has been relaxed. The ISM metallicity of X-ray fainter galaxies are uncertain, but at least SNe Ia contribution to the ISM abundance is smaller than in the X-ray luminous ones.
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Sánchez-Menguiano, L., S. F. Sánchez, I. Pérez, T. Ruiz-Lara, L. Galbany, J. P. Anderson, T. Krühler, H. Kuncarayakti, and J. D. Lyman. "The shape of oxygen abundance profiles explored with MUSE: evidence for widespread deviations from single gradients." Astronomy & Astrophysics 609 (January 2018): A119. http://dx.doi.org/10.1051/0004-6361/201731486.
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We characterised the oxygen abundance radial distribution of a sample of 102 spiral galaxies observed with VLT/MUSE using the O3N2 calibrator. The high spatial resolution of the data allowed us to detect 14345 H ii regions with the same image quality as with photometric data, avoiding any dilution effect. We developed a new methodology to automatically fit the abundance radial profiles, finding that 55 galaxies of the sample exhibit a single negative gradient. The remaining 47 galaxies also display, as well as this negative trend, either an inner drop in the abundances (21), an outer flattening (10), or both (16), which suggests that these features are a common property of disc galaxies. The presence and depth of the inner drop depends on the stellar mass of the galaxies with the most massive systems presenting the deepest abundance drops, while there is no such dependence in the case of the outer flattening. We find that the inner drop appears always around 0.5 re, while the position of the outer flattening varies over a wide range of galactocentric distances. Regarding the main negative gradient, we find a characteristic slope in the sample of αO/H =−0.10 ± 0.03 dex /re. This slope is independent of the presence of bars and the density of the environment. However, when inner drops or outer flattenings are detected, slightly steeper gradients are observed. This suggests that radial motions might play an important role in shaping the abundance profiles. We define a new normalisation scale (“the abundance scale length”, rO/H) for the radial profiles based on the characteristic abundance gradient, with which all the galaxies show a similar position for the inner drop (~0.5 rO/H) and the outer flattening (~1.5 rO/H). Finally, we find no significant dependence of the dispersion around the negative gradient with any property of the galaxies, with values compatible with the uncertainties associated with the derivation of the abundances.
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Roy, Jean-René. "Abundance Distributions in Barred Galaxies." International Astronomical Union Colloquium 157 (1996): 63–69. http://dx.doi.org/10.1017/s0252921100049423.
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AbstractI review the evidence for global abundance gradients in barred galaxies to be flatter when compared with those of normal galaxies. The finding that the abundance gradient becomes flatter as the strength of the bar increases, illustrates the effectiveness of radial flows induced by bars at transporting large amount of gas across galaxy disks.
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Verde, Licia, S. Peng Oh, and Raul Jimenez. "The abundance of dark galaxies." Monthly Notices of the Royal Astronomical Society 336, no. 2 (October 21, 2002): 541–49. http://dx.doi.org/10.1046/j.1365-8711.2002.05771.x.
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Angeletti, L., and P. Giannone. "Abundance gradients in elliptical galaxies." Astronomy & Astrophysics 403, no. 2 (May 2003): 449–62. http://dx.doi.org/10.1051/0004-6361:20030164.
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Tolstoy, Eline, and Kim Venn. "Stellar Abundances in Local Group Galaxies." Highlights of Astronomy 13 (2005): 548–53. http://dx.doi.org/10.1017/s1539299600016567.
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AbstractHere we describe some of our latest results from measuring detailed abundances in Local Group dwarf galaxies with the VLT. Combining spectroscopic abundances with Color-Magnitude diagrams allows the effective measurement of detailed chemical evolution with time in these galaxies. Although there are not yet significant numbers of individual stars observed in local group dwarf galaxies, the uniformity of the abundance patterns of the majority of stars in galaxies with very different star formation histories must hint at general properties of all star formation in these small systems.
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Mao, Junjie, Jelle de Plaa, Jelle S. Kaastra, Ciro Pinto, Liyi Gu, François Mernier, Hong-Liang Yan, Yu-Ying Zhang, and Hiroki Akamatsu. "Nitrogen abundance in the X-ray halos of clusters and groups of galaxies." Astronomy & Astrophysics 621 (December 19, 2018): A9. http://dx.doi.org/10.1051/0004-6361/201730931.
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Context. Chemical abundances in the X-ray halos (also known as the intracluster medium, ICM) of clusters and groups of galaxies can be measured via prominent emission line features in their X-ray spectra. Elemental abundances are footprints of time-integrated yields of various stellar populations that have left their specific abundance patterns prior to and during the cluster and group evolution. Aim. We aim to constrain nitrogen abundances in the CHEmical Evolution RGS Sample (CHEERS), which contains 44 nearby groups and clusters of galaxies, to gain a better understanding of their chemical enrichment. Method. We examined the high-resolution spectra of the CHEERS sample and took various systematic effects in the spectral modelling into account. We compared the observed abundance ratios with those in the Galactic stellar populations and also with predictions from stellar yields (low- and intermediate-mass stars, massive stars, and degenerate stars). Results. The nitrogen abundance can only be well constrained (≳3σ) in one cluster of galaxies and seven groups of galaxies. The [O/Fe] – [Fe/H] relation of the ICM is comparable to that for the Galaxy, while the [N/Fe] and [N/O] ratios of the ICM are both higher than in the Galaxy. Future studies on nitrogen radial distributions are required to tell whether the obtained higher [N/Fe] and [N/O] ratios are biased as a result of the small extraction region (r/r500 ≲ 0.05) that we adopt here. Since abundances of odd-Z elements are more sensitive to the initial metallicity of stellar populations, accurate abundance measurements of N, Na, and Al are required to better constrain the chemical enrichment in the X-ray halos of clusters and groups of galaxies.
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Douglass, Kelly A., Michael S. Vogeley, and Renyue Cen. "Influence of the Void Environment on Chemical Abundances in Dwarf Galaxies and Implications for Connecting Star Formation and Halo Mass." Proceedings of the International Astronomical Union 14, S344 (August 2018): 369–72. http://dx.doi.org/10.1017/s1743921318006816.
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AbstractWe study how the void environment affects the chemical evolution of galaxies by comparing the metallicity of dwarf galaxies in voids with dwarf galaxies in denser regions. Using spectroscopic observations from SDSS DR7, we estimate oxygen and nitrogen abundances of 889 void dwarf galaxies and 672 dwarf galaxies in denser regions. A substitute for the [OII] λ3727 doublet is developed, permitting oxygen abundance estimates of SDSS dwarf galaxies at all redshifts with the direct method. We find that void dwarf galaxies have about the same oxygen abundances and slightly lower N/O ratios than dwarf galaxies in denser environments. The lower N/O ratios seen in void dwarf galaxies may indicate both delayed star formation and a dependence of cosmic downsizing on the large-scale environment. Similar oxygen abundances in the two dwarf galaxy populations might be evidence of larger ratios of dark matter halo mass to stellar mass in voids.
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Lamarche, C., J. D. Smith, K. Kreckel, S. T. Linden, N. S. J. Rogers, E. Skillman, D. Berg, et al. "Direct Far-infrared Metal Abundances (FIRA). I. M101." Astrophysical Journal 925, no. 2 (February 1, 2022): 194. http://dx.doi.org/10.3847/1538-4357/ac3b4f.
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Abstract Accurately determining gas-phase metal abundances within galaxies is critical as metals strongly affect the physics of the interstellar medium. To date, the vast majority of widely used gas-phase abundance indicators rely on emission from bright optical lines, whose emissivities are highly sensitive to the electron temperature. Alternatively, direct-abundance methods exist that measure the temperature of the emitting gas directly, though these methods usually require challenging observations of highly excited auroral lines. Low-lying far-infrared (FIR) fine structure lines are largely insensitive to electron temperature and thus provide an attractive alternative to optically derived abundances. Here, we introduce the far-infrared abundance (FIRA) project, which employs these FIR transitions, together with both radio free–free emission and hydrogen recombination lines, to derive direct, absolute gas-phase oxygen abundances. Our first target is M101, a nearby spiral galaxy with a relatively steep abundance gradient. Our results are consistent with the O++ electron temperatures and absolute oxygen abundances derived using optical direct-abundance methods by the CHemical Abundance Of Spirals (CHAOS) program, with a small difference (∼1.5σ) in the radial abundance gradients derived by the FIR/free–free-normalized versus CHAOS/direct-abundance techniques. This initial result demonstrates the validity of the FIRA methodology—with the promise of determining absolute metal abundances within dusty star-forming galaxies, both locally and at high redshift.
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Matteucci, Francesca. "Chemical enrichment and feedback in low metallicity environments: constraints on galaxy formation." Proceedings of the International Astronomical Union 4, S255 (June 2008): 134–41. http://dx.doi.org/10.1017/s1743921308024708.
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AbstractChemical evolution models for dwarf metal poor galaxies, including dwarf irregulars and dwarf spheroidals will be presented. The main ingredients necessary to build detailed models of chemical evolution including stellar nucleosynthesis, supernova progenitors, stellar lifetimes and stellar feedback will be discussed. The stellar feedback will be analysed in connection with the development of galactic winds in dwarf galaxies and their effects on the predicted abundances and abundance ratios. Model results concerning α-elements (O, Mg, Si, Ca), Fe and s-and r-process elements will be discussed and compared with the most recent observational data for metal poor galaxies of the Local Group. We will show how the study of abundance ratios versus abundances can represent a very powerful tool to infer constraints on galaxy formation mechanisms. In this framework, we will discuss whether, on the basis of their chemical properties, the dwarf galaxies of the Local Group could have been the building blocks of the Milky Way.
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Matsushita, Kyoko, Yasushi Ikebe, Alexis Finoguenov, and Hans Böhringer. "XMM Observations of Abundances in the Intracluster Medium." Symposium - International Astronomical Union 217 (2004): 102–7. http://dx.doi.org/10.1017/s0074180900197220.
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Based on XMM-Newton observations of M 87 and the Centaurus cluster, abundance profiles of various elements of the intracluster medium (ICM) are derived. The abundances of Si and Fe show strong decreasing gradients. In contrast, the O and Mg abundances are about half of the Si abundance at the center.From the gas mass to stellar mass ratio and the comparison of Mg abundance with the stellar metallicity, the stellar mass loss from the central galaxies is indicated to be the main source of gas in the very central region of the clusters.The observed O, Si and Fe abundance pattern determines the contribution of supernova (SN) Ia and SN II, with the abundance pattern of ejecta of SN Ia. Most of the Si and Fe of the ICM in the central region of the clusters comes from SN Ia which occured in the central galaxies. In order to explain the observed O/Si ratio of a half solar, SN Ia products should have similar abundances of Si and Fe, which may reflect dimmer SN Ia observed in old stellar systems.
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Bresolin, Fabio. "Abundances and gradients in nearby galaxies." Proceedings of the International Astronomical Union 12, S323 (October 2016): 237–44. http://dx.doi.org/10.1017/s1743921317000503.
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AbstractThe study of chemical abundance gradients can provide essential information on the evolution of disk galaxies. Here I briefly review our current observational knowledge concerning the abundances of the ionized gas (H ii regions and planetary nebulae) in nearby galaxies, and how they inform us about the time evolution of metallicity gradients.
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Richer, M. G., M. L. McCall, and N. Arimoto. "Oxygen Abundances in Diffuse Ellipticals and the Metallicity-Luminosity Relation for Dwarf Galaxies." Symposium - International Astronomical Union 171 (1996): 439. http://dx.doi.org/10.1017/s0074180900233573.
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Using theoretical models of the planetary nebula populations in galaxies, we investigate whether the current oxygen abundances in bright planetary nebulae can be used to predict the oxygen abundance that persisted in the interstellar medium when star formation stopped. In all galaxies, these models predict that a gap develops between the abundances observed in bright planetary nebulae and those that persisted in the interstellar medium when star formation stopped. This abundance gap depends primarily upon the oxygen abundance achieved in the interstellar medium when star formation stopped, though it also has some sensitivity to the history of star formation. The gap is always less than 0.5dex in these models. For the Milky Way, the predicted abundance gap, 0.14dex, is identical to that observed. The abundance gap magnifies the abundance-related differences between diffuse ellipticals and dwarf irregulars found by Richer & McCall (1995, ApJ, 445, 642). Diffuse ellipticals are confirmed to have larger oxygen abundances than similarly luminous dwarf irregulars, and to have larger [O/Fe] ratios than dwarf irregulars with the same oxygen abundance. The simplest explanation for both of these observations is that diffuse ellipticals formed on shorter time scales than dwarf irregulars. Given this difference in the history of star formation, diffuse ellipticals cannot be the faded remnants of dwarf irregulars.
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Rodríguez, M., and C. Esteban. "The Iron Abundance in Blue Compact Galaxies." Symposium - International Astronomical Union 217 (2004): 198–99. http://dx.doi.org/10.1017/s0074180900197463.
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We determine the Fe abundances for several blue compact and emission-line galaxies. The O/Fe abundance ratios are found to increase with the metallicity of the galaxy, and to decrease with its degree of ionization. These correlations are interpreted as reflecting a decrease for lower metallicities of the depletion of Fe atoms on to dust grains, probably arising from the harder radiation fields prevailing at low metallicities.
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Gonçalves, Denise R., Laura Magrini, Lucimara P. Martins, Ana M. Teodorescu, Cintia Quireza, and Gaia Lanfranchi. "Deep spectroscopy of the dwarf spheroidal NGC 185." Proceedings of the International Astronomical Union 7, S283 (July 2011): 370–71. http://dx.doi.org/10.1017/s1743921312011477.
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AbstractDwarf galaxies are crucial to understand the formation and evolution of galaxies, since they constitute the most abundant galaxy population. Abundance ratios and their variations due to star formation and inflow/outflow of gas are key constraints to chemical evolution models. The determination of these abundances in the dwarf galaxies of the Local Universe is thus of extreme importance. NGC 185 is one of the four brightest dwarf companions of M31, but unlike the other three it has an important content of gas and dust. Interestingly enough, in an optical survey of bright nearby galaxies NGC 185 was classified as a Seyfert galaxy based on its integrated emission-line ratios in the nuclear regions. However, although its emission lines formally place it in the category of Seyfert it is probable that this galaxy does not contain a genuine active nucleus. In this contribution, we resume, firstly, our results of an empirical study of the galaxy, on which we characterise its emission-line population and obtain planetary nebulae abundance ratios (Gonçalves et al. 2012). And, secondly, we discuss our attempt to identify the possible ionization mechanisms for NGC 185 enlighting the controversial classification of this galaxy dwarf spheroidal (dSph) as well as Seyfert, via stellar population synthesis and chemical evolution modelling (Martins et al. 2011).
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Rau, Shiau-Jie, Hiroyuki Hirashita, and Maria Murga. "Modelling the evolution of PAH abundance in galaxies." Monthly Notices of the Royal Astronomical Society 489, no. 4 (September 11, 2019): 5218–24. http://dx.doi.org/10.1093/mnras/stz2532.
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ABSTRACT We investigate the evolution of polycyclic aromatic hydrocarbon (PAH) abundance in a galaxy, which is a crucial step to understand the evolution of bright emission features in the mid-infrared range. We calculate the evolution of dust grain size distribution in a manner consistent with the physical conditions of the interstellar medium by post-processing our previous hydrodynamical simulation of an isolated disc galaxy. We also differentiate between aromatic and non-aromatic grains for carbonaceous dust species and explicitly considered the aromatization process. As a consequence, our model explains the metallicity dependence of PAH abundances in nearby galaxies well. The PAH abundance increase is driven particularly by the interplay between shattering and accretion (dust growth). The fast aromatization guarantees that the small carbonaceous grains trace PAHs very well. Since shattering and accretion are sensitive to the dust abundance, we predict that the PAH-to-dust abundance ratio increases as the metallicity increases. This is consistent with the observation data of nearby galaxies.
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Truran, James W. "Chemical Evolution of Galaxies: Abundance Trends and Implications." Symposium - International Astronomical Union 145 (1991): 13–19. http://dx.doi.org/10.1017/s0074180900227228.
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Recent spectroscopic studies of the elemental abundance patterns associated with extremely metal deficient field halo stars and globular cluster stars are briefly reviewed. These metal deficient stellar populations have been found to be characterized by abundance patterns which differ quite distinctly from those of solar system abundances, but are consistent with the view that they reflect primarily the nucleosynthesis products of the evolution of massive stars and associated Type II supernovae. Guided by our current knowledge of nucleosynthesis as a function of stellar mass occurring in stars and supernovae, we identify some interesting constraints upon theories of the formation and early history of our Galaxy.
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Larsen, S. S., J. P. Brodie, A. Wasserman, and J. Strader. "Detailed abundance analysis of globular clusters in the Local Group." Astronomy & Astrophysics 613 (May 2018): A56. http://dx.doi.org/10.1051/0004-6361/201731909.
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Context. Globular clusters (GCs) are emerging as powerful tracers of the chemical composition of extragalactic stellar populations. Aims. We present new abundance measurements for 11 GCs in the Local Group galaxies NGC 147, NGC 6822, and Messier 33. These are combined with previously published observations of four GCs in the Fornax and Wolf–Lundmark–Melotte (WLM) galaxies. Methods. The abundances were determined from analyses of integrated-light spectra obtained with the HIRES spectrograph on the Keck I telescope and with UVES on the Very Large Telescope (VLT). We used our analysis technique that was developed for this purpose and tested on Milky Way GCs. Results. We find that the clusters with [Fe∕H] < −1.5 are all α-enhanced at about the same level as Milky Way GCs. Their Na abundances are also generally enhanced relative to Milky Way halo stars, suggesting that these extragalactic GCs resemble their Milky Way counterparts in containing large numbers of Na-rich stars. For [Fe∕H] > −1.5, the GCs in M33 are also α-enhanced, while the GCs that belong to dwarfs (NGC 6822 SC7 and Fornax 4) have closer to solar-scaled α-element abundances. The abundance patterns in SC7 are remarkably similar to those in the Galactic GC Ruprecht 106, including significantly subsolar [Na∕Fe] and [Ni∕Fe] ratios. In NGC 147, the GCs with [Fe∕H] < −2.0 account for about 6% of the total luminosity of stars in the same metallicity range, a lower fraction than those previously found in the Fornax and WLM galaxies, but substantially higher than in the Milky Way halo. Conclusions. At low metallicities, the abundance patterns suggest that GCs in the Milky Way, dwarf galaxies, and M33 experienced similar enrichment histories and/or processes. At higher metallicities, the lower levels of α-enhancement in the GCs found in dwarf galaxies resemble the abundance patterns observed in field stars in nearby dwarfs. Constraining the presence of multiple populations in these GCs is complicated by lack of information about detailed abundances in field stars of the corresponding metallicities. We suggest that correlations such as [Na∕Fe] versus [Ni∕Fe] may prove useful for this purpose if an accuracy of ~ 0.1 dex or better can be reached for integrated-light measurements.
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Dors, O. L., and M. V. F. Copetti. "Abundance segregation in Virgo spiral galaxies." Astronomy & Astrophysics 452, no. 2 (May 22, 2006): 473–80. http://dx.doi.org/10.1051/0004-6361:20054592.
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Zinchenko, I. A., L. S. Pilyugin, E. K. Grebel, S. F. Sánchez, and J. M. Vílchez. "Oxygen abundance maps of CALIFA galaxies." Monthly Notices of the Royal Astronomical Society 462, no. 3 (July 30, 2016): 2715–33. http://dx.doi.org/10.1093/mnras/stw1857.
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Şen, Ş., R. F. Peletier, A. Boselli, M. den Brok, J. Falcón-Barroso, G. Hensler, J. Janz, et al. "Abundance ratios in dwarf elliptical galaxies." Monthly Notices of the Royal Astronomical Society 475, no. 3 (December 20, 2017): 3453–66. http://dx.doi.org/10.1093/mnras/stx3254.
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Haurberg, Nathalie C., John J. Salzer, John M. Cannon, and Melissa V. Marshall. "OXYGEN ABUNDANCE MEASUREMENTS OF SHIELD GALAXIES." Astrophysical Journal 800, no. 2 (February 18, 2015): 121. http://dx.doi.org/10.1088/0004-637x/800/2/121.
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Venn, Kim A., Andreas Kaufer, Eline Tolstoy, Rolf-Peter Kudritzki, Norbert Przybilla, Stephen J. Smartt, and Daniel J. Lennon. "Chemical abundances of massive stars in Local Group galaxies." Symposium - International Astronomical Union 212 (2003): 30–37. http://dx.doi.org/10.1017/s0074180900211613.
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The relative abundances of elements in galaxies can provide valuable information on the stellar and chemical evolution of a galaxy. While nebulae can provide abundances for a variety of light elements, stars are the only way to directly determine the abundances of iron-group and s-process and r-process elements in a galaxy. The new 8m and 10m class telescopes and high-efficiency spectrographs now make high-quality spectral observations of bright supergiants possible in dwarf galaxies in the Local Group. We have been concentrating on elemental abundances in the metal-poor dwarf irregular galaxies, NGC 6822, WLM, Sextants A, and GR 8. Comparing abundance ratios to those predicted from their star formation histories, determined from color-magnitude diagrams, and comparing those ratios between these galaxies can give us new insights into the evolution of these dwarf irregular galaxies. Iron-group abundances also allow us to examine the metallicities of the stars in these galaxies directly, which affects their inferred mass loss rates and predicted stellar evolution properties.
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Larsen, S. S., P. Eitner, E. Magg, M. Bergemann, C. A. S. Moltzer, J. P. Brodie, A. J. Romanowsky, and J. Strader. "The chemical composition of globular clusters in the Local Group." Astronomy & Astrophysics 660 (April 2022): A88. http://dx.doi.org/10.1051/0004-6361/202142243.
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We present detailed chemical abundance measurements for 45 globular clusters (GCs) associated with galaxies in (and, in one case, beyond) the Local Group. The measurements are based on new high-resolution integrated-light spectra of GCs in the galaxies NGC 185, NGC 205, M 31, M 33, and NGC 2403, combined with reanalysis of previously published observations of GCs in the Fornax dSph, WLM, NGC 147, NGC 6822, and the Milky Way. The GCs cover the range −2.8 < [Fe/H] < −0.1 and we determined abundances for Fe, Na, Mg, Si, Ca, Sc, Ti, Cr, Mn, Ni, Cu, Zn, Zr, Ba, and Eu. Corrections for non local thermodynamic equilibrium effects are included for Na, Mg, Ca, Ti, Mn, Fe, Ni, and Ba, building on a recently developed procedure. For several of the galaxies, our measurements provide the first quantitative constraints on the detailed composition of their metal-poor stellar populations. Overall, the GCs in different galaxies exhibit remarkably uniform abundance patterns of the α, iron-peak, and neutron-capture elements, with a dispersion of less than 0.1 dex in [α/Fe] for the full sample. There is a hint that GCs in dwarf galaxies are slightly less α-enhanced (by ∼0.04 dex on average) than those in larger galaxies. One GC in M 33 (HM33-B) resembles the most metal-rich GCs in the Fornax dSph (Fornax 4) and NGC 6822 (SC7) by having α-element abundances closer to scaled-solar values, possibly hinting at an accretion origin. A principal components analysis shows that the α-element abundances strongly correlate with those of Na, Sc, Ni, and Zn. Several GCs with [Fe/H] < −1.5 are deficient in Mg compared to other α-elements. We find no GCs with strongly enhanced r-process abundances as reported for metal-poor stars in some ultra-faint dwarfs and the Magellanic Clouds. The similarity of the abundance patterns for metal-poor GCs in different environments points to similar early enrichment histories and only allow for minor variations in the initial mass function.
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Pilyugin, L. S., E. K. Grebel, I. A. Zinchenko, Y. A. Nefedyev, V. M. Shulga, H. Wei, and P. P. Berczik. "Validity of abundances derived from spaxel spectra of the MaNGA survey." Astronomy & Astrophysics 613 (May 2018): A1. http://dx.doi.org/10.1051/0004-6361/201732185.
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We measured the emission lines in the spaxel spectra of Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) galaxies in order to determine the abundance distributions therein. It has been suggested that the strength of the low-ionization lines, R2, N2, and S2, may be increased (relative to Balmer lines) in (some) spaxel spectra of the MaNGA survey due to a contribution of the radiation of the diffuse ionized gas. Consequently, the abundances derived from the spaxel spectra through strong-line methods may suffer from large errors. We examined this expectation by comparing the behaviour of the line intensities and the abundances estimated through different calibrations for slit spectra of H II regions in nearby galaxies, for fibre spectra from the Sloan Digital Sky Survey, and for spaxel spectra of the MaNGA survey. We found that the S2 strength is increased significantly in the fibre and spaxel spectra. The mean enhancement changes with metallicity and can be as large as a factor of ~2. The mean distortion of R2 and N2 is less than a factor of ~1.3. This suggests that Kaufmann et al.’s (2003, MNRAS, 346, 1055) demarcation line between active galactic nuclei and H II regions in the Baldwin, Phillips, & Terlevich (BPT, 1981, PASP, 93, 5) diagram is a useful criterion to reject spectra with significantly distorted strengths of the N2 and R2 lines. We find that the three-dimensional R calibration, which uses the N2 and R2 lines, produces reliable abundances in the MaNGA galaxies. The one-dimensional N2 calibration produces either reliable or wrong abundances depending on whether excitation and N/O abundance ratio in the target region (spaxel) are close to or differ from those parameters in the calibrating points located close to the calibration relation. We then determined abundance distributions within the optical radii in the discs of 47 MaNGA galaxies. The optical radii of the galaxies were estimated from the surface brightness profiles constructed based on the MaNGA observations.
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Zurita, A., E. Florido, F. Bresolin, E. Pérez-Montero, and I. Pérez. "Bar effect on gas-phase abundance gradients. I. Data sample and chemical abundances." Monthly Notices of the Royal Astronomical Society 500, no. 2 (August 18, 2020): 2359–79. http://dx.doi.org/10.1093/mnras/staa2246.
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ABSTRACT Studies of gas-phase radial metallicity profiles in spirals published in the last decade have diminished the importance of galactic bars as agents that mix and flatten the profiles, contradicting results obtained in the 1990s. We have collected a large sample of 2831 published H ii region emission-line fluxes in 51 nearby galaxies, including objects both with and without the presence of a bar, with the aim of revisiting the issue of whether bars affect the radial metal distribution in spirals. In this first paper of a series of two, we present the galaxy and the H ii region samples. The methodology is homogeneous for the whole data sample and includes the derivation of H ii region chemical abundances, structural parameters of bars and discs, galactocentric distances, and radial abundance profiles. We have obtained O/H and N/O abundance ratios from the Te-based (direct) method for a subsample of 610 regions, and from a variety of strong-line methods for the whole H ii region sample. The strong-line methods have been evaluated in relation to the Te-based one from both a comparison of the derived O/H and N/O abundances for individual H ii regions and a comparison of the abundance gradients derived from both methodologies. The median value and the standard deviation of the gradient distributions depend on the abundance method, and those based on the O3N2 indicator tend to flatten the steepest profiles, reducing the range of observed gradients. A detailed analysis and discussion of the derived O/H and N/O radial abundance gradients and y-intercepts for barred and unbarred galaxies is presented in the companion Paper II. The whole H ii region catalogue including emission-line fluxes, positions, and derived abundances is made publicly available on the CDS VizieR facility, together with the radial abundance gradients for all galaxies.
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Doughty, Caitlin, and Kristian Finlator. "The effects of binary stars on galaxies and metal-enriched gas during reionization." Monthly Notices of the Royal Astronomical Society 505, no. 2 (May 21, 2021): 2207–23. http://dx.doi.org/10.1093/mnras/stab1448.
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ABSTRACT Binary stars are abundant in nearby galaxies, but are typically unaccounted for in simulations of the high-redshift Universe. Stellar population synthesis models that include the effects of binary evolution result in greater relative abundances of ionizing photons that could significantly affect the ambient ionizing background during the epoch of hydrogen reionization, additionally leading to differences in galaxy gas content and star formation. We use hydrodynamic cosmological simulations including in situ multifrequency radiative transfer to evaluate the effects of a high binary fraction in reionization-era galaxies on traits of the early intergalactic medium and the abundance of H i and He ii ionizing photons. We further extend this to analyse the traits of enriched gas. In comparing metrics generated using a fiducial simulation assuming single stars with one incorporating a high binary fraction, we find that binary stars cause H i reionization to complete earlier and at an accelerated pace, while also increasing the abundances of high-ionization metals (C iv and Si iv) in simulated absorption spectra while reducing the abundance of low-ionization states (O i, Si ii, and C ii). However, through increased photoheating of galactic and circumgalactic gas, they simultaneously reduce the rate of star formation in low-mass galaxies, slowing the ongoing process of enrichment and suppressing their own ionizing background. This potentially contributes to a slower He ii reionization process at $z\ge 5$, and further indicates that self-regulation of galaxies could be underestimated when neglecting binary stellar evolution.
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Díaz, Ángeles I., and S. Zamora. "On the use of sulphur as a tracer for abundances in galaxies." Monthly Notices of the Royal Astronomical Society 511, no. 3 (February 12, 2022): 4377–92. http://dx.doi.org/10.1093/mnras/stac387.
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Abstract 2+We present a methodology for the use of sulphur as global metallicity tracer in galaxies, allowing performing a complete abundance analysis using only the red-to-near-infrared spectral region. We have applied it to a compilation of high-quality data split into two samples: H ii regions (DHR) in spiral and irregular galaxies, and dwarf galaxies dominated by a strong starburst (H ii Gal). Sulphur abundances have been derived by direct methods under the assumption of an ionization structure composed of two zones: an intermediate-ionization one where S++ is originated, and a low-ionization one where S+ is formed. Ionization correction factors (ICF) have been calculated from the Ar/Ar3+ ratio and are shown to correlate with the hardness of the radiation field. Only about 10 per cent of the objects show S3+ contributions to the total abundance larger than 30 per cent. A good correlation exists between sulphur abundance and ionizing temperature with low-metallicity objects being ionized by hotter stars. No correlation is found between ionization parameter and total S/H abundance. Most of the H ii Gal objects show S/O ratios below the solar value and a trend for increasing S/O ratios with increasing sulphur abundances, while DHR objects show S/O ratios larger than solar and a tendency for lower S/O ratios for higher metallicities. Finally, we present a calibration of the sulphur abundance through the S23 parameter that remains single valued up to sulphur abundances well beyond the solar value. S23 is independent of the ionization parameter and only weakly dependent on ionizing temperature.
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Long, Knox S. "Supernova Remnants in Nearby Spiral Galaxies." International Astronomical Union Colloquium 145 (1996): 349–56. http://dx.doi.org/10.1017/s0252921100008204.
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Large samples of supernova remnants are needed in order to study the global distribution of supernovae in galaxies, for determining how the environment in which a SN explodes affects the appearance of a SNR, for studying abundances and abundance gradients in galaxies, for estimating SN rates, and in order to determine the energetics of SNRs and their expansion. Here we describe techniques which are currently being used to expand SNR samples in nearby spirals.
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Frebel, Anna, Joshua D. Simon, Evan Kirby, Marla Geha, and Beth Willman. "Extremely metal-poor stars in dwarf galaxies." Proceedings of the International Astronomical Union 5, S265 (August 2009): 237–40. http://dx.doi.org/10.1017/s1743921310000633.
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AbstractWe present Keck/HIRES spectra of six metal-poor stars in two of the ultra-faint dwarf galaxies orbiting the Milky Way, Ursa Major II and Coma Berenices, and a Magellan/MIKE spectrum of a star in the classical dwarf spheroidal galaxy (dSph) Sculptor. Our data include the first high-resolution spectroscopic observations of extremely metal-poor stars ([Fe/H] < −3.0) not belonging to the Milky Way (MW) stellar halo field population. We obtain abundance measurements and upper limits for up to 26 elements between carbon and europium. The stars span a range of −3.8 < [Fe/H] < −2.3, with the ultra-faints having large spreads in Fe. A comparison with MW halo stars of similar metallicity reveals substantial agreement between the abundance patterns of the ultra-faint dwarf galaxies and Sculptor and the MW halo for the light, α and iron-peak elements (C to Zn). This agreement contrasts with the results of earlier studies of more metal-rich stars (−2.5 ≲[Fe/H]≲ −1.0) in more luminous dwarfs, which found significant abundance discrepancies with respect to the MW halo data. The abundances of neutron-capture elements (Sr to Eu) in all three galaxies are extremely low, consistent with the most metal-poor halo stars, but not with the typical halo abundance pattern at [Fe/H]≳ −3.0. Our results are broadly consistent with a galaxy formation model which predicts that massive dwarf galaxies are the source of the metal-rich component ([Fe/H]≳ −2.5) of the MW inner halo, but we propose that dwarf galaxies similar to the dSphs are the primary contributors to the metal-poor end of the metallicity distribution of the MW outer halo.
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Miller, John H., John J. Salzer, Steven Janowiecki, Martha P. Haynes, and Alec S. Hirschauer. "Searches for Extremely Metal-poor Galaxies Using Arecibo Legacy Fast ALFA–Selected Dwarf Galaxies *." Astrophysical Journal 943, no. 2 (January 27, 2023): 93. http://dx.doi.org/10.3847/1538-4357/aca89b.
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Abstract We present a study of nearby dwarf galaxies selected from the Arecibo Legacy Fast ALFA (ALFALFA) blind H i survey. A primary goal of the project was to utilize a nonstandard selection method with the hope of detecting previously unrecognized extremely metal-poor (XMP) galaxies. The study was motivated by the recent discovery of two XMP galaxies, Leo P and Leoncino, which were both originally found via the ALFALFA survey. We have obtained narrowband Hα images for 42 dwarf systems, many of which are located in the Local Void in front of the Pisces–Perseus Supercluster. Spectra for 11 of the best candidates resulted in the determination of metal abundances for 10 of the systems. None were found to be extremely metal-poor, although one system (AGC 123350) was found to have an oxygen abundance of log(O/H)+12 = 7.46, or ∼6% solar. One of the galaxies in our sample exhibits a high oxygen abundance for its luminosity, suggesting the possibility that it may have a tidal origin.
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Parkash, Vaishali, Michael J. I. Brown, T. H. Jarrett, A. Fraser-McKelvie, and M. E. Cluver. "H i galaxies with little star formation: an abundance of LIERs." Monthly Notices of the Royal Astronomical Society 485, no. 3 (March 2, 2019): 3169–84. http://dx.doi.org/10.1093/mnras/stz593.
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Abstract We present a sample of 91 H i galaxies with little or no star formation, and discuss the analysis of the integral field unit (IFU) spectra of 28 of these galaxies. We identified H i galaxies from the H i Parkes All-Sky Survey Catalog (HICAT) with Wide-field Infrared Survey Explorer (WISE) colours consistent with low specific star formation (<10−10.4 yr−1), and obtained optical IFU spectra with the Wide-Field Spectrograph (WiFeS). Visual inspection of the PanSTARRS, Dark Energy Survey, and Carnegie-Irvine imaging of 62 galaxies reveals that at least 32 galaxies in the sample have low levels of star formation, primarily in arms/rings. New IFU spectra of 28 of these galaxies reveals 3 galaxies with central star formation, 1 galaxy with low-ionization nuclear emission-line regions (LINERs), 20 with extended low-ionization emission-line regions (LIERs), and 4 with high excitation Seyfert (Sy) emission. From the spectroscopic analysis of H i selected galaxies with little star formation, we conclude that 75 per cent of this population are LINERs/LIERs.
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Johansson, Jonas, Daniel Thomas, and Claudia Maraston. "The Chemical Enrichment Histories of SDSS Galaxies." Proceedings of the International Astronomical Union 6, S277 (December 2010): 174–77. http://dx.doi.org/10.1017/s174392131102271x.
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AbstractWe derive the full chemical enrichment histories for 3800 early-type galaxies, including both star forming and passively evolving systems. For this purpose we have developed a method to simultaneously derive the element abundance ratios [C/Fe], [N/Fe], [Mg/Fe], [Ca/Fe] and [Ti/Fe] for unresolved stellar populations. The method is based on up-to-date stellar population models with varying element abundance ratios. A novelty of the models is that they are flux-calibrated, removing the dependence on the Lick/IDS system. Trends with velocity dispersion are investigated where [Mg/Fe] and [C/Fe] are found to show very similar trends, while [N/Fe] show overall lower abundances ratios. [Ca/Fe] ratios are close to solar values over the velocity dispersion range covered. Tentative, due to large scatter, result for [Ti/Fe] implies that Ti follow the trends of Ca.
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Patrick, Lee R., Chris J. Evans, Ben Davies, Rolf-Peter Kudritzki, Maria Bergemann, and Annette N. M. Ferguson. "Red Supergiants as Chemical Abundance Probes: The Local Group dwarf NGC6822." Proceedings of the International Astronomical Union 14, S344 (August 2018): 213–16. http://dx.doi.org/10.1017/s174392131800649x.
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AbstractRed Supergiant Stars (RSGs) are important probes of stellar and chemical evolution in star-forming environments. They represent the brightest near-IR stellar components of external galaxies and probe the most recent stellar population to provide robust, independent abundance estimates. The Local Group dwarf irregular galaxy, NGC6822, is a reasonably isolated galaxy with an interesting structure and turbulent history. Using RSGs as chemical abundance probes, we estimate metallicities in the central region of NGC6822, finding a suggestion of a metallicity gradient (in broad agreement with nebular tracers), however, this requires further study for confirmation. With intermediate resolution Multi-object spectroscopy (from e.g. KMOS, EMIR, MOSFIRE) combined with state-of-the-art stellar model atmospheres, we demonstrate how RSGs can be used to estimate stellar abundances in external galaxies. In this context, we compare stellar and nebular abundance tracers in NGC 6822 and by combining stellar and nebular tracers we estimate an abundance gradient of −0.18 ± 0.05 dex/kpc.
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Gyulzadyan, M. V., and V. Z. Adibekyan. "The physical conditions and oxygen and nitrogen abundance of 36 SBS galaxies from the SDSS DR7." Proceedings of the International Astronomical Union 9, S304 (October 2013): 34–35. http://dx.doi.org/10.1017/s1743921314003226.
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AbstractPhysical conditions and oxygen and nitrogen abundances in 36 SBS UV-excess and/or emission-line galaxies from the SDSS DR7 were determined. We have found that SBS 0808+578 is AGN. The others are HII galaxies or HII regions in galaxies. For all objects the oxygen abundance 12+log(O/H) lies in the range of 7.85 ÷ 8.61 and log(N/O) ratio in the range of −1.45 ÷ −0.4. They occupy the same area in the diagram N/O O/H as the high-excitation HII regions. We found no extremely metal-deficient galaxy. Using H-alpha fluxes star formation rates (SFR) for our samples galaxies were determined. Determined SFRs, being in the range of 0.001 ÷ 6 o year−1, are similar of that observed in typical star forming regions in spiral and irregular galaxies.
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Rosales-Ortega, Fernando Fabián. "The Study of Nebular Emission on Nearby Spiral Galaxies in the IFU Era." Advances in Astronomy 2013 (2013): 1–14. http://dx.doi.org/10.1155/2013/627867.
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A new generation of wide-field emission-line surveys based on integral field units (IFU) is allowing us to obtain spatially resolved information of the gas-phase emission in nearby late-type galaxies, based on large samples of HII regions and full two-dimensional coverage. These observations are allowing us to discover and characterise abundance differentials between galactic substructures and new scaling relations with global physical properties. Here I review some highlights of our current studies employing this technique: (1) the case study of NGC 628, the largest galaxy ever sampled with an IFU; (2) a statistical approach to the abundance gradients of spiral galaxies, which indicates auniversalradial gradient for oxygen abundance; and (3) the discovery of a new scaling relation of HII regions in spiral galaxies, thelocalmass-metallicity relation of star-forming galaxies. The observational properties and constrains found in local galaxies using this new technique will allow us to interpret the gas-phase abundance of analogue high-z systems.
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Arellano-Córdova, Karla Z., Danielle A. Berg, John Chisholm, Pablo Arrabal Haro, Mark Dickinson, Steven L. Finkelstein, Floriane Leclercq, et al. "A First Look at the Abundance Pattern—O/H, C/O, and Ne/O—in z > 7 Galaxies with JWST/NIRSpec." Astrophysical Journal Letters 940, no. 1 (November 1, 2022): L23. http://dx.doi.org/10.3847/2041-8213/ac9ab2.
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Abstract We analyze the rest-frame near-UV and optical nebular spectra of three z > 7 galaxies from the Early Release Observations taken with the Near-Infrared Spectrograph (NIRSpec) on the James Webb Space Telescope (JWST). These three high-z galaxies show the detection of several strong emission nebular lines, including the temperature-sensitive [O iii] λ4363 line, allowing us to directly determine the nebular conditions and abundances for O/H, C/O, and Ne/O. We derive O/H abundances and ionization parameters that are generally consistent with other recent analyses. We analyze the mass–metallicity relationship (i.e., slope) and its redshift evolution by comparing between the three z > 7 galaxies and local star-forming galaxies. We also detect the C iii] λλ1907, 1909 emission in a z > 8 galaxy from which we determine the most distant C/O abundance to date. This valuable detection of log(C/O) = −0.83 ± 0.38 provides the first test of C/O redshift evolution out to high redshift. For neon, we use the high-ionization [Ne iii] λ3869 line to measure the first Ne/O abundances at z > 7, finding no evolution in this α-element ratio. We explore the tentative detection of [Fe ii] and [Fe iii] lines in a z > 8 galaxy, which would indicate a rapid buildup of metals. Importantly, we demonstrate that properly flux-calibrated and higher-S/N spectra are crucial to robustly determine the abundance pattern in z > 7 galaxies with NIRSpec/JWST.