Redshift Evolution of Damped Lyman Alpha Absorbers and the Epoch of Galaxy Formation

1993 ◽  
Vol 688 (1) ◽  
pp. 545-550
Author(s):  
ANNE L. KINNEY ◽  
RICHARD L. WHITE ◽  
ROBERT H. BECKER
Keyword(s):  
Galaxy Formation ◽  
Lyman Alpha

scholarly journals Simulations of the Intergalactic Medium

2005 ◽  
Vol 216 ◽  
pp. 251-265
Author(s):  
Romeel Davé
Keyword(s):  
Absorption Line ◽  
Galaxy Formation ◽  
Intergalactic Medium ◽  
Ultraviolet Absorption ◽  
Multiple Populations ◽  
Hydrodynamic Simulations ◽  
Lyman Alpha ◽  
Lyman Alpha Forest ◽  
Working Together

I present an epochal review of baryons in the intergalactic medium (IGM), from the reionization epoch until today. Recent observations indicate a protracted period of reionization, suggesting multiple populations of reionizers; detection of these z ≳ 6 sources is a key goal that is now coming within reach. The optical Lyman alpha forest (2 ≲ z ≲ 4) is well-described by the Fluctuating Gunn-Peterson Approximation, but recent observations of galaxies and metal lines associated with Lyα absorbers remain puzzling. IGM studies at z ≲ 1.5 are progressing rapidly thanks to ultraviolet absorption line studies of both Lyα absorbers and the warm-hot intergalactic medium. Cosmological hydrodynamic simulations have played an integral part in these advances, and have helped to revolutionize our understanding of the IGM at various epochs. Working together, observations and theory continue to expand our knowledge of the IGM as the earliest stage of galaxy formation and the dominant reservoir of baryons at all redshifts.

scholarly journals Damped Lyman alpha systems and galaxy formation models - II. High ions and Lyman-limit systems

2003 ◽  
Vol 343 (1) ◽  
pp. 268-278 ◽  
Author(s):  
A. H. Maller ◽  
J. X. Prochaska ◽  
R. S. Somerville ◽  
J. R. Primack
Keyword(s):  
Galaxy Formation ◽  
Lyman Alpha ◽  
Damped Lyman Alpha Systems

scholarly journals Physical Properties of Dlas: Metallicity and Neutral Hydrogen Column Density

2004 ◽  
Vol 217 ◽  
pp. 246-251
Author(s):  
J. L. Hou ◽  
C. G. Shu ◽  
W. P. Chen ◽  
R. X. Chang ◽  
C. Q. Fu
Keyword(s):  
Star Formation ◽  
Galaxy Formation ◽  
Column Density ◽  
High Redshift ◽  
Formation Rate ◽  
Neutral Hydrogen ◽  
Gas Content ◽  
Lyman Alpha ◽  
Formation Mode ◽  
Damped Lyman Alpha Systems

We investigate some basic properties of Damped Lyman alpha systems based on the Semi-Analytical model of disk galaxy formation theory. We derive the DLA metallicity, column density, number density, gas content and cosmic star formation rate by assuming that disks form at the center of dark halos, and the modelled DLAs are selected by Monte Carlo simulation according to the distributions of halo properties. We find that DLA hosts are dominated by small galaxies and biased to extended galaxies. In terms of model results, DLAs could naturally arise in a ACDM universe from radiatively cooled gas in dark matter halos. However, model predicts a reverse correlation between metallicity and the column density when compared with observations, regardless of the proposed observational bias. We argue that this could be resulted from the model limitations, or the inadequacy of Schmidt-type star formation mode at high redshift, or/and the diversities of DLA populations.

scholarly journals Lyman-alpha radiation pressure: an analytical exploration

2021 ◽  
Vol 504 (1) ◽  
pp. 89-100
Author(s):  
G M Tomaselli ◽  
A Ferrara
Keyword(s):  
Radiation Pressure ◽  
Galaxy Formation ◽  
Column Density ◽  
Dominant Role ◽  
The Other ◽  
Alpha Radiation ◽  
Star Forming ◽  
Lyman Alpha ◽  
Initial Acceleration ◽  
Analytical Expressions

ABSTRACT We study radiation pressure due to Ly α line photons, obtaining and exploring analytical expressions for the force-multiplier, MF(NH, Z) = Fα/(Lα/c), as a function of gas column density, NH, and metallicity, Z, for both dust-free and dusty media, employing a WKB approach for the latter case. Solutions for frequency offset emission to emulate non-static media moving with a bulk velocity v have also been obtained. We find that, in static media, Ly α pressure dominates over both photoionization and dust-mediated UV radiation pressure in a very wide parameter range (16 < log NH < 23; −4 < log [Z/Z⊙] < 0). For example, it overwhelms the other two forces by $\lower.5ex\hbox{$\,\, \buildrel\gt \over \sim \,\,$}10$ (300) times in standard (low-Z) star-forming clouds. Thus, in agreement with previous studies, we conclude that Ly α pressure plays a dominant role in the initial acceleration of the gas around luminous sources, and must be implemented in galaxy formation, evolution and outflow models and simulations.

scholarly journals A Lyα nebula at z ∼ 3.3

2020 ◽  
Vol 641 ◽  
pp. A32
Author(s):  
P. Hibon ◽  
F. Tang ◽  
R. Thomas
Keyword(s):  
Galaxy Formation ◽  
High Redshift ◽  
Broad Band ◽  
Observational Cosmology ◽  
Redshift Range ◽  
High Redshift Galaxies ◽  
Star Forming ◽  
Lyman Alpha ◽  
Multi Wavelength ◽  
Intense Activity

Context. Searching for high-redshift galaxies is a field of intense activity in modern observational cosmology that will continue to grow with future ground-based and sky observatories. Over the last few years, a lot has been learned about the high-z Universe. Aims. Despite extensive Lyα blobs (LAB) surveys from low to high redshifts, giant LABs over 100 kpc have been found mostly at z ∼ 2–4. This redshift range is coincident with the transition epoch of galactic gas-circulation processes from inflows to outflows at z ∼ 2.5–3. This suggests that the formation of giant LABs may be related to a combination of gas inflows and outflows. Their extreme youth makes them interesting objects in the study of galaxy formation as they provide insight into some of the youngest known highly star forming galaxies, with only modest time investments using ground-based telescopes. Methods. Systematic narrow-band Lyα nebula surveys are ongoing, but they are limited in their covered redshift range and their comoving volume. This poses a significant problem when searching for such rare sources. To address this problem, we developed a systematic searching tool, ATACAMA (A Tool for seArChing for lArge LyMan Alpha nebulae) designed to find large Lyα nebulae at any redshift within deep multi-wavelength broad-band imaging. Results. We identified a Lyα nebula candidate at zphot ∼ 3.3 covering an isophotal area of 29.4arcsec2. Its morphology shows a bright core and a faint core which coincides with the morphology of previously known Lyα blobs. A first estimation of the Lyα equivalent width and line flux agree with the values from the study led by several groups.

Damped Lyman-alpha systems and galaxy formation

1994 ◽  
Vol 430 ◽  
pp. L25 ◽  
Author(s):  
H. J. Mo ◽  
J. Miralda-Escude
Keyword(s):  
Galaxy Formation ◽  
Lyman Alpha ◽  
Damped Lyman Alpha Systems

New evidence from the Lyman-alpha forest concerning the formation of galaxies

1986 ◽  
Vol 320 (1556) ◽  
pp. 503-515 ◽  
Keyword(s):  
Galaxy Formation ◽  
Galactic Plane ◽  
Normal Population ◽  
Mass Density ◽  
Density Parameter ◽  
Redshift Distribution ◽  
Lyman Alpha ◽  
New Type ◽  
Nearby Galaxies ◽  
Damped Systems

A new type of survey for galaxies with z > 2 will be described. The idea is to search for the spectroscopic imprint that the H1 disc of a foreground galaxy leaves on radiation emitted by a background Qso; namely, a Lyman-α absorption line broadened by radiation damping. A continuing survey has revealed the presence of 15 damped Lα lines with redshifts between 1.8 and 2.8 in the spectra of 68 QSOS. In comparison, no more than three discs with the properties of nearby galaxies should have been detected. Furthermore, the mean column density of the 15 absorbers, <(N(H1)> = 1.4 x 10 21 cm -2 , is much larger than expected for the outskirts of H1 discs. Both statistical and physical evidence has accumulated which suggests that the damped Lα systems are a distinct population of absorbers with properties reminiscent of H1 discs. First, the Lyman-α absorption lines detected in the survey follow a frequency distribution of equivalent width that cannot be due to previously detected cloud populations. At large equivalent widths, where the damped Lα lines occur, a new population of absorbers must exist. This damped population is therefore unrelated to clouds that are known to differ physically from galaxy discs. Secondly, detailed studies of the damped population reveal many of the properties shared by the H1 discs of galaxies. For example, ( a ) the absorption spectra due to ions of abundant elements are dominated by low ions such as C + , Si + and Fe + , instead of C3 + and Si 3+ , which are usually seen and ( b ) the recent detection of 21 cm absorption at z = 2.04 in one of the damped systems shows that the H1 is cold and that it has a low level of turbulence (σ ≈ 10 km s -1 ). Another piece of evidence connecting the damped population with discs is that the cosmological mass density of the absorbers is characterized by a density parameter, Ω≈ 3 x 10 -3 / h . This is comparable to the Ω due to luminous baryons. We suggest that this agreement is not coincidental, but rather reflects the fact that we have detected the progenitors of the baryon content of nearby galaxies. The discovery of the damped population has a number of implications for theories of galaxy formation. First, if the damped absorbers are identified with the normal population of galaxies, the H1 discs at z > 2 have radii ≈ 3 R HO (Holmberg). Because their redshift distribution is consistent with formation at z > 2.8, the production of large H1 discs from the collapse of protogalaxies must occur more rapidly (within less than 3 Ga) than predicted in many theories. Secondly, the collapse to discs of present size must occur in the galactic plane rather than from the halo.

scholarly journals Galaxy Formation: Confrontation with Observations

1987 ◽  
Vol 124 ◽  
pp. 391-413
Author(s):  
Joseph Silk
Keyword(s):  
Dark Matter ◽  
Star Formation ◽  
Galaxy Formation ◽  
Cold Dark Matter ◽  
Dwarf Galaxies ◽  
Density Fluctuations ◽  
Inflationary Cosmology ◽  
Lyman Alpha ◽  
Gaussian Density

The implications for galaxy formation of inflationary cosmology are reviewed. In particular, I explore some implications of the hypothesis that galaxies form from adiabatic, gaussian density fluctuations in a cold dark matter–dominated universe. Topics discussed include protogalaxies and the epoch of galaxy formation, Lyman alpha clouds, dark halos and dwarf galaxies. Finally I describe how environmental biasing may arise as a consequence of tidally induced star formation in protoclusters.

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