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Journal articles on the topic 'Spectral line formation Congresses'

Author: Grafiati

Published: 29 July 2024

Last updated: 31 July 2025

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1

Paletou, F., and C. Peymirat. "Full non–LTE spectral line formation." Astronomy & Astrophysics 649 (May 2021): A165. http://dx.doi.org/10.1051/0004-6361/202040005.

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Radiative transfer out of local thermodynamic equilibrium (NLTE) has been increasingly adressed, mostly numerically, for about six decades now. However, the standard NLTE problem most often refers to the only deviation of the distribution of photons from their equilibrium, that is to say a Planckian distribution. Hereafter we revisit after Oxenius (1986, Kinetic theory of particles and Photons – Theoretical Foundations of non–LTE Plasma Spectroscopy, Springer) the so-called full NLTE problem, which considers coupling and therefore solving self–consistently for deviations from equilibrium distr

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2

Oxenius, J., and E. Simonneau. "Kinetic Theory of Spectral Line Formation." Annals of Physics 234, no. 1 (1994): 60–101. http://dx.doi.org/10.1006/aphy.1994.1074.

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Klevas, J., A. Kučinskas, M. Steffen, E. Caffau, and H. G. Ludwig. "Lithium spectral line formation in stellar atmospheres." Astronomy & Astrophysics 586 (February 2016): A156. http://dx.doi.org/10.1051/0004-6361/201526403.

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4

Peraiah, A., and M. Srinivasa Rao. "Compton broadening effect on spectral line formation." Astrophysics and Space Science 343, no. 1 (2012): 195–211. http://dx.doi.org/10.1007/s10509-012-1233-0.

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5

Nikoghossian, A. G. "Spectral line formation in a mesoturbulent atmosphere." Astrophysics 50, no. 2 (2007): 175–86. http://dx.doi.org/10.1007/s10511-007-0017-7.

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6

Vieytes, Mariela C., Lily L. Zhao, and Megan Bedell. "The Influence of Chromospheric Activity on Line Formation." Astrophysical Journal 981, no. 1 (2025): 4. https://doi.org/10.3847/1538-4357/adb0c6.

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Abstract One of the primary sources of stellar spectral variability is magnetic activity. While our current understanding of chromospheric activity is largely derived from specific lines sensitive to chromospheric heating, such as the Ca ii H and K doublet, previous observational studies have shown that other spectral lines are also affected. To investigate the influence of activity on line formation in greater detail, we constructed a set of stellar models for hypothetical G2 dwarf stars with varying levels of activity and calculated their synthetic spectra. A comparison of these spectra reve

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Grec, C., H. Uitenbroek, M. Faurobert, and C. Aime. "Measuring line formation depths by cross-spectral analysis." Astronomy and Astrophysics 514 (May 2010): A91. http://dx.doi.org/10.1051/0004-6361/200811455.

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8

Letunov, Andrey Yu, and Valery S. Lisitsa. "Review of Rydberg Spectral Line Formation in Plasmas." Atoms 11, no. 10 (2023): 133. http://dx.doi.org/10.3390/atoms11100133.

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The present review is dedicated to the problem of an array of transitions between highly-excited atomic levels. Hydrogen atoms and hydrogen-like ions in plasmas are considered here. The presented methods focus on calculation of spectral line shapes. Fast and simple methods of universal ionic profile calculation for the Hnα (Δn=1) and Hnβ (Δn=2) spectral lines are demonstrated. The universal dipole matrix elements formulas for the Hnα and Hnβ transitions are presented. A fast method for spectral line shape calculations in the presence of an external magnetic field using the formulas for univers

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9

Albrow, Michael D., and P. L. Cottrell. "Formation Depths of Spectral Lines in Cepheids." International Astronomical Union Colloquium 155 (1995): 373–74. http://dx.doi.org/10.1017/s0252921100037568.

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There has been a number of observational programmes that have endeavoured to investigate the atmospheric velocity fields in Cepheids (e.g., Sanford 1956, Wallerstein et al. 1992, Butler 1993). These studies measured the radial velocities of lines of different strength, excitation and ionisation potential as these provide an indication of line formation at different levels in the atmosphere. From these measurements, the presence of velocity gradients can be inferred, but determination of the magnitude of such gradients requires knowledge of the spectral line depth of formation. Through dynamica

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10

Dravins, Dainis. "Observed and computed spectral line profiles." Symposium - International Astronomical Union 176 (1996): 519–22. http://dx.doi.org/10.1017/s0074180900083534.

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For the diagnostics of stellar surface structure, studies of “ordinary” line profiles may prove inadequate. However, hydrodynamic models may be constrained by second-order quantities, such as line asymmetries and wavelength shifts (and especially the differential behavior between lines of different excitation potential, ionization stage, and height of formation, as well as by the time dependence).

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11

Ivonina, Liudmila. "The Triumph of Peace: International Congresses and European Society in the Time of Courts and Alliances." ISTORIYA 13, no. 1 (111) (2022): 0. http://dx.doi.org/10.18254/s207987840018801-0.

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The formation of the first state system in Europe took place from the conclusion of the Peace of Westphalia in 1648, as a result of the Thirty Years&apos; War (1618-1648), to the Utrecht (1713) and Rastatt-Baden (1714) Congresses which finished the end of the war of the Spanish Succession. The legal fixation of the Westphallian system was accompanied by its public perception and acceptance. First of all, this was demonstrated by International Congresses, which were not only a common negotiation process, but also a place of representation of the significance and culture of each state. In fa

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12

Kravchenko, K., S. Van Eck, A. Chiavassa, A. Jorissen, B. Freytag, and B. Plez. "Tomography of cool giant and supergiant star atmospheres." Astronomy & Astrophysics 610 (February 2018): A29. http://dx.doi.org/10.1051/0004-6361/201731530.

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Context. Cool giant and supergiant star atmospheres are characterized by complex velocity fields originating from convection and pulsation processes which are not fully understood yet. The velocity fields impact the formation of spectral lines, which thus contain information on the dynamics of stellar atmospheres. Aim. The tomographic method allows to recover the distribution of the component of the velocity field projected on the line of sight at different optical depths in the stellar atmosphere. The computation of the contribution function to the line depression aims at correctly identifyin

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13

Collet, R., M. Asplund, and F. Thévenin. "Effects of line-blocking on the non-LTE Fe I spectral line formation." Astronomy & Astrophysics 442, no. 2 (2005): 643–50. http://dx.doi.org/10.1051/0004-6361:20053363.

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14

Tichý, A., J. Štěpán, J. Trujillo Bueno, and J. Kubát. "Formation of polarized spectral lines in atmospheres with horizontal inhomogeneities." Proceedings of the International Astronomical Union 10, S305 (2014): 401–6. http://dx.doi.org/10.1017/s1743921315005128.

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AbstractWe study the problem of the generation and transfer of spectral line intensity and polarization in models of stellar atmospheres with horizontal plasma inhomogeneities. We solve the non-LTE radiative transfer problem in full 3D geometry taking into account resonant scattering polarization and its modification by magnetic fields via the Hanle effect. We show that horizontal fluctuations of the thermodynamical conditions of stellar atmospheres can have a significant impact on the linear polarization of the emergent spectral line radiation and its center-to-limb variation.

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15

Drew, J. E. "On spectral line formation in winds from extended continuum sources." Monthly Notices of the Royal Astronomical Society 218, no. 1 (1986): 41P—47P. http://dx.doi.org/10.1093/mnras/218.1.41p.

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16

Rosato, J. "Spectral line formation with wave effects in optically thick plasmas." Journal of Physics: Conference Series 397 (December 6, 2012): 012018. http://dx.doi.org/10.1088/1742-6596/397/1/012018.

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17

Fabbian, D., M. Asplund, M. Carlsson, and D. Kiselman. "CI non–LTE spectral line formation in late-type stars." Proceedings of the International Astronomical Union 1, S228 (2005): 255–56. http://dx.doi.org/10.1017/s1743921305005703.

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18

Israelian, G. "The effect of continuum scattering processes on spectral line formation." Journal of Quantitative Spectroscopy and Radiative Transfer 67, no. 4 (2000): 293–301. http://dx.doi.org/10.1016/s0022-4073(99)00238-1.

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19

Amarsi, A. M. "On line contribution functions and examining spectral line formation in 3D model stellar atmospheres." Monthly Notices of the Royal Astronomical Society 452, no. 2 (2015): 1612–16. http://dx.doi.org/10.1093/mnras/stv1392.

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20

Hayek, W., M. Asplund, R. Collet, and Å. Nordlund. "3D LTE spectral line formation with scattering in red giant stars." Astronomy & Astrophysics 529 (April 22, 2011): A158. http://dx.doi.org/10.1051/0004-6361/201015782.

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21

Rangarajan, K. E., D. Mohan Rao, and A. Peraiah. "The effects of non-coherent electron scattering on spectral line formation." Monthly Notices of the Royal Astronomical Society 250, no. 3 (1991): 633–37. http://dx.doi.org/10.1093/mnras/250.3.633.

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22

Wang, Ella Xi, Thomas Nordlander, Martin Asplund, Anish M. Amarsi, Karin Lind, and Yixiao Zhou. "3D NLTE spectral line formation of lithium in late-type stars." Monthly Notices of the Royal Astronomical Society 500, no. 2 (2020): 2159–76. http://dx.doi.org/10.1093/mnras/staa3381.

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ABSTRACT Accurately known stellar lithium abundances may be used to shed light on a variety of astrophysical phenomena such as big bang nucleosynthesis, radial migration, ages of stars and stellar clusters, and planet engulfment events. We present a grid of synthetic lithium spectra that are computed in non-local thermodynamic equilibrium (NLTE) across the stagger grid of three-dimensional (3D) hydrodynamic stellar atmosphere models. This grid covers three Li lines at 610.4, 670.8, and 812.6 nm for stellar parameters representative of FGK-type dwarfs and giants, spanning Teff = 4000–7000 K, lo

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23

Barichello, L. B., and C. E. Siewert. "The FN method for spectral-line formation by completely noncoherent scattering." Journal of Quantitative Spectroscopy and Radiative Transfer 60, no. 2 (1998): 261–76. http://dx.doi.org/10.1016/s0022-4073(97)00171-4.

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24

Antia, H. M. "A Model for Stellar Convection and Spectral Line Asymmetries." Symposium - International Astronomical Union 138 (1990): 417–20. http://dx.doi.org/10.1017/s0074180900044417.

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A model for stellar convection zones based on linear convective modes using a nonlocal mixing length theory is developed to study the spectral line asymmetries and the line shifts resulting from convective motions in the stellar photospheric region. The amplitudes of these linear convective modes is estimated by requiring the convective flux due to a linear superposition of such modes to reproduce the convective flux in the mixing length model. To study the spectral line asymmetries the convective mode with the largest amplitude in the photospheric line formation region is chosen to represent

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25

Štěpán, J. "Three-dimensional simulations of scattering polarization and the Hanle effect in MHD chromospheric models." Proceedings of the International Astronomical Union 10, S305 (2014): 360–67. http://dx.doi.org/10.1017/s1743921315005050.

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AbstractScattering line polarization and the Hanle effect are among the most important mechanisms for diagnostics of the solar and stellar atmospheres. The fact that real stellar atmospheres are horizontally inhomogeneous makes the spectral synthesis and interpretation very challenging because the effect of thermodynamic fluctuations on spectral line polarization is entangled with the action of magnetic fields. This applies to the spatially resolved as well as to the averaged spectra. The necessary step towards the interpretation of such spectra is to study the line formation in sufficiently r

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26

Kubát, Jiří, Jiří Krtička, Izold B. Pustylnik, and Viktor Votruba. "The Possibility of a Disk Formation around Late B Stars." Symposium - International Astronomical Union 215 (2004): 49–50. http://dx.doi.org/10.1017/s007418090019518x.

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Line driven wind in late B stars causes significant heating of layers just above the photosphere. This large heating is a source of a thermal wind, which together with fast rotation opens the possibility of a formation of a disk. We refer to such disk as to a radiation induced disk. Disk inhibition by nonradial line force has only little effect in this case, since absorption in spectral lines is not the main wind driving mechanism.

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27

Torres-Papaqui, J. P., R. Coziol, and R. A. Ortega-Minakata. "The Chemical Evolution of Narrow Emission Line Galaxies: the Key to their Formation Processes." Acta Universitaria 21 (September 1, 2011): 82–91. http://dx.doi.org/10.15174/au.2011.39.

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Using the largest sample of narrow emission line galaxies available so far, we show that their spectral characteristics are correlated with different physical parameters, like the chemical abundances, the morphologies, the masses of the bulge and the mean stellar age of the stellar populations of the host galaxies. It suggests that the spectral variations observed in standard spectroscopic diagnostic diagrams are not due solely to variations of ionization parameters or structures but reflect also the chemical evolution of the galaxies, which in turn can be explained by different galaxy formati

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28

Lisitsa, Valery, Mikhail Kadomtsev, Vladislav Kotov, Vladislav Neverov, and Vladimir Shurygin. "Hydrogen Spectral Line Shape Formation in the SOL of Fusion Reactor Plasmas." Atoms 2, no. 2 (2014): 195–206. http://dx.doi.org/10.3390/atoms2020195.

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29

Sabbey, C. N., D. D. Sasselov, M. S. Fieldus, J. B. Lester, K. A. Venn, and R. P. Butler. "On Spectral Line Formation and Measurement in Cepheids: Implications to Distance Determination." Astrophysical Journal 446 (June 1995): 250. http://dx.doi.org/10.1086/175783.

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30

Sapar, A., and L. Sapar. "Formation of resonance spectral line profiles in stellar wind: Theory and observations." Astronomical & Astrophysical Transactions 18, no. 3 (1999): 475–85. http://dx.doi.org/10.1080/10556799908203004.

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31

Kosarev, N. I. "Formation of the contour of a spectral line upon partial frequency redistribution." Optics and Spectroscopy 102, no. 1 (2007): 8–14. http://dx.doi.org/10.1134/s0030400x0701002x.

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32

Medvid', Artur, Pavels Onufrijevs, Edvins Dauksta, and Volodymyr Kyslyi. "“Black Silicon” Formation by Nd:YAG Laser Radiation." Advanced Materials Research 222 (April 2011): 44–47. http://dx.doi.org/10.4028/www.scientific.net/amr.222.44.

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The possibility to form “black silicon” on the surface of Si structure by Nd:YAG laser radiation has been shown. The shape and height of micro-cone structure strongly depends on Nd:YAG laser intensity and number of laser pulses. Light is repeatedly reflected between the cones in the way that most of it is absorbed. Si micro-cone structure spectral thermal radiation is close to black body spectral radiance, which makes this structure useful for solar cells application. The micro-chemical analysis performed by SEM has shown that the microstructures contain NiSi2. This was approved by presence of

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33

Frémat, Y., J. Zorec, A. M. Hubert, et al. "Fast Rotating Stars: Effect of the Aspect Angle on Line Profiles." Symposium - International Astronomical Union 215 (2004): 23–24. http://dx.doi.org/10.1017/s0074180900195117.

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Fast rotation is expected to flatten the star and to produce non uniform temperature and density distributions (i.e. gravitational darkening). While the flattening mostly increases the absolute flux level of the energy distribution, gravitational darkening makes an equator-on star apparently cooler than a star seen through the pole. Both effects (Collins et al. 1991) influence the colours and the location of the star in the HR diagram but also, in a more subtle way, its spectral line profiles. More particularly, in early B type stars, gravitational darkening tends to privilege at the poles the

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34

Steinbach, Julia C., Markus Schneider, Otto Hauler, Günter Lorenz, Karsten Rebner, and Andreas Kandelbauer. "A Process Analytical Concept for In-Line FTIR Monitoring of Polysiloxane Formation." Polymers 12, no. 11 (2020): 2473. http://dx.doi.org/10.3390/polym12112473.

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The chemical synthesis of polysiloxanes from monomeric starting materials involves a series of hydrolysis, condensation and modification reactions with complex monomeric and oligomeric reaction mixtures. Real-time monitoring and precise process control of the synthesis process is of great importance to ensure reproducible intermediates and products and can readily be performed by optical spectroscopy. In chemical reactions involving rapid and simultaneous functional group transformations and complex reaction mixtures, however, the spectroscopic signals are often ambiguous due to overlapping ba

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35

Roth, M., A. Herrero, R. H. Mendez, R. P. Kudritzki, K. Butler, and H. G. Groth. "The Metal-Line Spectra of Central Stars of Planetary Nebulae." Symposium - International Astronomical Union 131 (1989): 317. http://dx.doi.org/10.1017/s0074180900138653.

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We present spectral descriptions based on high-resolution spectrograms of central stars of planetary nebulae, obtained with the ESO 3,6-m telescope + CASPEC (Cassegrain Echelle Spectrograph). We make preliminary determinations of stellar photospheric metal abundances, using non-LTE model atmospheres and non-LTE line formation calculations.

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36

Toriumi, Shin, Vladimir S. Airapetian, Kosuke Namekata, and Yuta Notsu. "Universal Scaling Laws for Solar and Stellar Atmospheric Heating: Catalog of Power-law Index between Solar Activity Proxies and Various Spectral Irradiances." Astrophysical Journal Supplement Series 262, no. 2 (2022): 46. http://dx.doi.org/10.3847/1538-4365/ac8b15.

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Abstract The formation of extremely hot outer atmospheres is one of the most prominent manifestations of magnetic activity common to late-type dwarf stars, including the Sun. It is widely believed that these atmospheric layers, the corona, transition region, and chromosphere, are heated by the dissipation of energy transported upwards from the stellar surface by the magnetic field. This is signified by the spectral line fluxes at various wavelengths, scaled with power-law relationships against the surface magnetic flux over a wide range of formation temperatures, which are universal to the Sun

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37

Evans, Neal J., Lee G. Mundy, John H. Davis, and Paul Vanden Bout. "Sub-Millimeter Spectral Line Observations in Very Dense Regions." Symposium - International Astronomical Union 115 (1987): 173. http://dx.doi.org/10.1017/s0074180900095322.

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In a search for very high density (n ≳ 107 cm−3) regions, the Millimeter Wave Observatory 5-m telescope was used to observe several submillimeter lines. The regions studied were Orion A, M17, S140, and NGC2024. The lines were CS(J=7-6), H2CO(JK-1K1=515→414), and HCN(J=4-3). These data are combined with data at millimeter wavelengths to derive the volume density and the results are compared to those deduced from millimeter lines alone (Snell et al. 1984). In NGC2024, higher densities (≳ 107 cm−3) are clearly indicated by the sub-mm lines than were derived by Snell et al. In M17, derived densiti

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38

Beuther, H., J. C. Mottram, A. Ahmadi, et al. "Fragmentation and disk formation during high-mass star formation." Astronomy & Astrophysics 617 (September 2018): A100. http://dx.doi.org/10.1051/0004-6361/201833021.

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Context. High-mass stars form in clusters, but neither the early fragmentation processes nor the detailed physical processes leading to the most massive stars are well understood. Aims. We aim to understand the fragmentation, as well as the disk formation, outflow generation, and chemical processes during high-mass star formation on spatial scales of individual cores. Methods. Using the IRAM Northern Extended Millimeter Array (NOEMA) in combination with the 30 m telescope, we have observed in the IRAM large program CORE the 1.37 mm continuum and spectral line emission at high angular resolutio

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39

Mordini, Sabrina, Luigi Spinoglio, and Juan Antonio Fernández-Ontiveros. "Calibration of mid- to far-infrared spectral lines in galaxies." Astronomy & Astrophysics 653 (September 2021): A36. http://dx.doi.org/10.1051/0004-6361/202140696.

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Context. Mid- to far-infrared (IR) lines are suitable in the study of dust-obscured regions in galaxies because dust extinction strongly decreases with wavelength, and therefore IR spectroscopy allows us to explore the most hidden regions of galaxies, where heavily obscured star formation as well as accretion onto supermassive black holes at the nuclei of galaxies occur. This is mostly important for the so-called cosmic noon (i.e. at redshifts of 1 < z < 3), at which point most of the baryonic mass in galaxies has been assembled. Aims. Our goal is to provide reliable calibrations of the

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40

Couston, Laurent, Dominique Pouyat, Christophe Moulin, and Pierre Decambox. "Speciation of Uranyl Species in Nitric Acid Medium by Time-Resolved Laser-Induced Fluorescence." Applied Spectroscopy 49, no. 3 (1995): 349–53. http://dx.doi.org/10.1366/0003702953963553.

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The aim of this work is the development of an on-line analytical procedure for uranyl trace determination in the nuclear fuel reprocessing process using time-resolved laser-induced fluorescence. Because the uranyl fluorescence spectrum is strongly affected by the nitrate concentration, knowledge of composition of the medium is necessary to normalize measurements. This paper reports the assumptions made on the spectral distortion, leading to a spectral deconvolution model. Uranyl complex formation constants are obtained from the spectral deconvolution and validate the method. In this way, spect

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41

Koribalski, B. S. "Overview on Spectral Line Source Finding and Visualisation." Publications of the Astronomical Society of Australia 29, no. 3 (2012): 359–70. http://dx.doi.org/10.1071/as12030.

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AbstractHere I will outline successes and challenges for finding spectral line sources in large data cubes that are dominated by noise. This is a 3D challenge as the sources we wish to catalog are spread over several spatial pixels and spectral channels. While 2D searches can be applied, e.g. channel by channel, optimal searches take into account the 3-dimensional nature of the sources. In this overview I will focus on Hi 21-cm spectral line source detection in extragalactic surveys, in particular HIPASS, the Hi Parkes All-Sky Survey and WALLABY, the ASKAP Hi All-Sky Survey. I use the original

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42

van den Broeke, J., P. S. Ross, A. W. C. van der Helm, E. T. Baars, and L. C. Rietveld. "Use of on-line UV/Vis-spectrometry in the measurement of dissolved ozone and AOC concentrations in drinking water treatment." Water Science and Technology 57, no. 8 (2008): 1169–75. http://dx.doi.org/10.2166/wst.2008.137.

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The concentrations of dissolved ozone and assimilable organic carbon (AOC) are important performance parameters in drinking water production. For the measurement of ozone, a spectral algorithm was developed that allows quantification in situ using a UV/Vis spectrometer probe. Furthermore, a strong correlation between the change in the absorption spectrum after individual treatment steps and the formation or removal of AOC in that treatment step was observed. This allowed the development of a spectral algorithm that predicts AOC formation during ozonation and subsequent removal in further treat

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43

Marziani, Paola, Edi Bon, Natasa Bon, et al. "Quasars: From the Physics of Line Formation to Cosmology." Atoms 7, no. 1 (2019): 18. http://dx.doi.org/10.3390/atoms7010018.

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Quasars accreting matter at very high rates (known as extreme Population A (xA) or super-Eddington accreting massive black holes) provide a new class of distance indicators covering cosmic epochs from the present-day Universe up to less than 1 Gyr from the Big Bang. The very high accretion rate makes it possible that massive black holes hosted in xA quasars can radiate at a stable, extreme luminosity-to-mass ratio. This in turn translates into stable physical and dynamical conditions of the mildly ionized gas in the quasar low-ionization line emitting region. In this contribution, we analyze t

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44

Dionatos, Odysseas, Tom Ray, and Manuel Güdel. "Herschel spectral-line mapping of the HH211 protostellar system." Astronomy & Astrophysics 616 (August 2018): A84. http://dx.doi.org/10.1051/0004-6361/201833057.

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Context. Mid- and far-infrared observations of the environment around embedded protostars reveal a plethora of high-excitation molecular and atomic emission lines. A number of different mechanisms for the origin of these lines have been proposed, including shocks induced by protostellar jets and radiation by the embedded protostar interacting with its immediate surroundings. Aims. We employ extended spectral-line maps that spatially resolve regions where diverse excitation processes appear to dominate. Studying the morphology and excitation of the most important molecular and atomic coolants,

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45

Giraud, E., J. Melnick, Q. S. Gu, et al. "Galaxy Evolution in a Pilot Survey up toz=1and CDM Halos." Advances in Astronomy 2011 (2011): 1–13. http://dx.doi.org/10.1155/2011/508381.

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We study spectral evolution of galaxies in a magnitude limited sample of 550 galaxies fromz=1down toz=0.3on a pencil beam of≈10′×10′. We concentrate on the large apparent cosmological structures along the line of sight, and we bin our individual galaxy spectra to obtain representative high S/N spectra based upon these structures. We divide the resulting average spectra in three groups to facilitate the analysis:galaxies with pure absorption line spectra, galaxies with emission lines and blue continua, and galaxies with emission lines and red continua. We revisit the question of downsizing in e

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46

Saha, Anindya, Anandmayee Tej, Hong-Li Liu, et al. "Direct Observational Evidence of Multi-epoch Massive Star Formation in G24.47+0.49." Astrophysical Journal Letters 970, no. 2 (2024): L40. http://dx.doi.org/10.3847/2041-8213/ad6144.

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Abstract Using new continuum and molecular line data from the Atacama Large Millimeter/submillimeter Array Three-millimeter Observations of Massive Star-forming Regions (ATOMS) survey and archival Very Large Array, 4.86 GHz data, we present direct observational evidence of hierarchical triggering relating three epochs of massive star formation in a ringlike H ii region, G24.47+0.49. We find from radio flux analysis that it is excited by a massive star(s) of spectral type O8.5V–O8V from the first epoch of star formation. The swept-up ionized ring structure shows evidence of secondary collapse,

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Beuther, H., Y. Wang, J. Soler, et al. "Dynamical cloud formation traced by atomic and molecular gas." Astronomy & Astrophysics 638 (June 2020): A44. http://dx.doi.org/10.1051/0004-6361/202037950.

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Context. Atomic and molecular cloud formation is a dynamical process. However, kinematic signatures of these processes are still observationally poorly constrained. Aims. We identify and characterize the cloud formation signatures in atomic and molecular gas. Methods. Targeting the cloud-scale environment of the prototypical infrared dark cloud G28.3, we employed spectral line imaging observations of the two atomic lines HI and [CI] as well as molecular lines observations in 13CO in the 1–0 and 3–2 transitions. The analysis comprises investigations of the kinematic properties of the different

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Marco, Amparo, and Ignacio Negueruela. "Triggered massive star formation in the open cluster NGC 1893." Symposium - International Astronomical Union 212 (2003): 562–63. http://dx.doi.org/10.1017/s0074180900212862.

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We have carried out a search for emission line pre-main sequence (PMS) stars in the area of the star-forming young open cluster NGC 1893 by means of slitless spectroscopy. We find 19 emission line stars with spectral types spanning the range from early B-type to G-type. All the PMS stars are confined to two small regions: the outer rim of the molecular cloud associated with the H ii region IC 410 and the vicinity of the bright emission cometary nebulae Sim 129 and Sim 130. The overall spatial distribution of PMS stars strongly suggests, that present day star formation in NGC 1893 is triggered

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Ott, Jürgen, David S. Meier, Nico Krieger, and Matthew Rickert. "SWAG: Survey of Water and Ammonia in the Galactic Center." Proceedings of the International Astronomical Union 11, S322 (2016): 143–44. http://dx.doi.org/10.1017/s1743921316011789.

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AbstractSWAG (“Survey of Water and Ammonia in the Galactic Center”) is a multi-line interferometric survey toward the Center of the Milky Way conducted with the Australia Telescope Compact Array. The survey region spans the entire ~400 pc Central Molecular Zone and comprises ~42 spectral lines at pc spatial and sub-km/s spectral resolution. In addition, we deeply map continuum intensity, spectral index, and polarization at the frequencies where synchrotron, free-free, and thermal dust sources emit. The observed spectral lines include many transitions of ammonia, which we use to construct maps

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Bose, Souvik, Vasco M. J. Henriques, Jayant Joshi, and Luc Rouppe van der Voort. "Characterization and formation of on-disk spicules in the Ca II K and Mg II k spectral lines." Astronomy & Astrophysics 631 (November 2019): L5. http://dx.doi.org/10.1051/0004-6361/201936617.

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We characterize, for the first time, type-II spicules in Ca II K 3934 Å using the CHROMIS instrument at the Swedish 1 m Solar Telescope. We find that their line formation is dominated by opacity shifts with the K3 minimum best representing the velocity of the spicules. The K2 features are either suppressed by the Doppler-shifted K3 or enhanced via increased contribution from the lower layers, leading to strongly enhanced but unshifted K2 peaks, with widening towards the line core as consistent with upper-layer opacity removal via Doppler-shift. We identify spicule spectra in concurrent IRIS Mg

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