scholarly journals HCN Observations of Dense Star-forming Gas in High-Redshift Galaxies

2007 ◽  
Vol 660 (2) ◽  
pp. L93-L96 ◽  
Author(s):  
Yu Gao ◽  
Chris L. Carilli ◽  
Philip M. Solomon ◽  
Paul A. Vanden Bout
Keyword(s):  
High Redshift ◽  
High Redshift Galaxies ◽  
Star Forming ◽  
Redshift Galaxies

Spectral Modeling of Star‐forming Regions in the Ultraviolet: Stellar Metallicity Diagnostics for High‐Redshift Galaxies

2004 ◽  
Vol 615 (1) ◽  
pp. 98-117 ◽  
Author(s):  
Samantha A. Rix ◽  
Max Pettini ◽  
Claus Leitherer ◽  
Fabio Bresolin ◽  
Rolf‐Peter Kudritzki ◽  
...  
Keyword(s):  
High Redshift ◽  
Spectral Modeling ◽  
High Redshift Galaxies ◽  
Star Forming ◽  
Star Forming Regions ◽  
Redshift Galaxies

scholarly journals Was the Milky Way Bulge Formed from the Buckling Disk Instability, Hierarchical Collapse, Accretion of Clumps, or All of the Above?

2017 ◽  
Vol 34 ◽  
Author(s):  
David M. Nataf
Keyword(s):  
Stellar Population ◽  
Milky Way ◽  
Velocity Dispersion ◽  
High Redshift ◽  
Rapid Development ◽  
High Redshift Galaxies ◽  
Star Forming ◽  
Thin And Thick Disks ◽  
Bulge Formation ◽  
Redshift Galaxies

AbstractThe assembly of the Milky Way bulge is an old topic in astronomy, one now in a period of renewed and rapid development. That is due to tremendous advances in observations of bulge stars, motivating observations of both local and high-redshift galaxies, and increasingly sophisticated simulations. The dominant scenario for bulge formation is that of the Milky Way as a nearly pure disk galaxy, with the inner disk having formed a bar and buckled. This can potentially explain virtually all bulge stars with [Fe/H] ≳ −1.0, which comprise 95% of the stellar population. The evidence is the incredible success in N-body models of this type in making non-trivial, non-generic predictions, such as the rotation curve and velocity dispersion measured from radial velocities, and the spatial morphologies of the peanut/X-shape and the long bar. The classical bulge scenario, whereby the bulge formed from early dissipative collapse and mergers, remains viable for stars with [Fe/H] ≲ −1.0 and potentially a minority of the other stars. A classical bulge is expected from Λ-CDM cosmological simulations, can accentuate the properties of an existing bar in a hybrid system, and is most consistent with the bulge abundance trends such as [Mg/Fe], which are elevated relative to both the thin and thick disks. Finally, the clumpy-galaxy scenario is considered, as it is the correct description of most Milky Way precursors given observations of high-redshift galaxies. Simulations predict that these star-forming clumps will sometimes migrate to the centres of galaxies where they may form a bulge, and galaxies often include a bulge clump as well. They will possibly form a bar with properties consistent with those of the Milky Way, such as the exponential profile and metallicity gradient. Given the relative successes of these scenarios, the Milky Way bulge is plausibly of composite origin, with a classical bulge and/or inner halo numerically dominant for stars with [Fe/H] ≲ −1.0, a buckling thick disk for stars with − 1.0 ≲ [Fe/H]] ≲ -0.50 perhaps descended from the clumpy-galaxy phase, and a buckling thin disk for stars with [Fe/H] ≳ −0.50. Overlaps from these scenarios are uncertain throughout.

scholarly journals A Comparison of Star-forming Clumps and Tidal Tails in Local Mergers and High-redshift Galaxies

2021 ◽  
Vol 908 (2) ◽  
pp. 121
Author(s):  
Debra Meloy Elmegreen ◽  
Bruce G. Elmegreen ◽  
Bradley C. Whitmore ◽  
Rupali Chandar ◽  
Daniela Calzetti ◽  
...  
Keyword(s):  
High Redshift ◽  
High Redshift Galaxies ◽  
Star Forming ◽  
Tidal Tails ◽  
Redshift Galaxies

scholarly journals Local analogs of high-redshift galaxies: Metallicity calibrations at high-redshift

2019 ◽  
Vol 15 (S352) ◽  
pp. 309-313
Author(s):  
Fuyan Bian ◽  
Lisa J. Kewley ◽  
Brent Groves ◽  
Michael A. Dopita
Keyword(s):  
Gas Phase ◽  
High Redshift ◽  
High Redshift Galaxies ◽  
Star Forming ◽  
Redshift Galaxies

AbstractWe study the metallicity calibrations in high-redshift galaxies using a sample of local analogs of high-redshift galaxies selected from the SDSS survey. Located in the same region on the BPT diagram as star-forming galaxies at z ∼ 2, these high-redshift analogs share the same ionized ISM conditions as high-redshift galaxies. We establish empirical metallicity calibrations between the direct gas-phase oxygen abundances and varieties of metallicity indicators in our local analogs using direct Te method. These new metallicity calibrations are the best means to measure the metallicity in high-redshift galaxies. There exist significant offsets between these new high-redshift metallicity calibrations and local calibrations. Such offsets are mainly driven by the evolution of the ionized ISM conditions from high-z to low-z.

scholarly journals Hierarchical fragmentation in high redshift galaxies revealed by hydrodynamical simulations

2021 ◽  
Author(s):  
Baptiste Faure ◽  
Frédéric Bournaud ◽  
Jérémy Fensch ◽  
Emanuele Daddi ◽  
Manuel Behrendt ◽  
...  
Keyword(s):  
Gravitational Lensing ◽  
Hubble Space Telescope ◽  
High Redshift ◽  
High Redshift Galaxies ◽  
Star Forming ◽  
Low Mass ◽  
Hydrodynamical Simulations ◽  
Gas Clusters ◽  
Very High ◽  
Redshift Galaxies

Abstract High-redshift star-forming galaxies have very different morphologies compared to nearby ones. Indeed, they are often dominated by bright star-forming structures of masses up to 108 − 9 M⊙ dubbed «giant clumps». However, recent observations questioned this result by showing only low-mass structures or no structure at all. We use Adaptative Mesh Refinement hydrodynamical simulations of galaxies with parsec-scale resolution to study the formation of structures inside clumpy high-redshift galaxies. We show that in very gas-rich galaxies star formation occurs in small gas clusters with masses below 107 − 8 M⊙ that are themselves located inside giant complexes with masses up to 108 and sometimes 109 M⊙ . Those massive structures are similar in mass and size to the giant clumps observed in imaging surveys, in particular with the Hubble Space Telescope. Using mock observations of simulated galaxies, we show that at very high resolution with instruments like the Atacama Large Millimeter Array or through gravitational lensing, only low-mass structures are likely to be detected, and their gathering into giant complexes might be missed. This leads to the non-detection of the giant clumps and therefore introduces a bias in the detection of these structures. We show that the simulated giant clumps can be gravitationally bound even when undetected in mocks representative for ALMA observations and HST observations of lensed galaxies. We then compare the top-down fragmentation of an initially warm disc and the bottom-up fragmentation of an initially cold disc to show that the process of formation of the clumps does not impact their physical properties.

scholarly journals Damped Lyα systems as probes of chemical evolution over cosmological timescales

2008 ◽  
Vol 4 (S255) ◽  
pp. 121-128
Author(s):  
Miroslava Dessauges-Zavadsky
Keyword(s):  
Star Formation ◽  
High Redshift ◽  
Large Contribution ◽  
High Redshift Galaxies ◽  
Star Forming ◽  
Current State ◽  
Galaxy Population ◽  
Stellar Masses ◽  
Star Formation Histories ◽  
Redshift Galaxies

AbstractWe review the current state of knowledge of damped Lyα systems (DLAs) selected in absorption on quasar sightlines. These objects are extremely useful to study the interstellar medium of high-redshift galaxies and the nucleosynthesis in the early Universe. The characteristics of this galaxy population has been investigated for years and slowly we are getting information on their puzzling nature. Imaging atz<1 shows that DLAs are associated with a mixing bag of galaxies with no especially large contribution from dwarf galaxies. Evidence for a mild evolution of the cosmic mean metallicity with time is observed. The star formation histories of these high-redshift galaxies begin to be accessible and indicate that DLAs tend to be young, gas-dominated galaxies with low star formation rates per unit area. Finally, indirect estimation of the DLA stellar masses from the mass-metallicity relations observed for emission-selected star-forming galaxies atz= 2−3 points to intermediate-mass galaxies withM*< 109M⊙.

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