153 research outputs found
Bias and Conditional Mass Function of Dark Halos Based on the Nonspherical Collapse Model
No full textThe Role of Major Galaxy Interactions in Galaxy Evolution Since Redshift z ~ 1
No full textWe present the close, kinematic pair fraction and merger rate up to redshift for a large sample of
galaxies observed by the DEEP2 Redshift Survey. The effect of the galaxy interactions/mergers has also been
addressed by studying the infrared luminosity to the stellar mass ratios speir for galaxies using images
taken by the Advanced Camera for Surveys in and and MIPS in 24m.
Assuming a mild luminosity evolution, the number of companions per luminous galaxy is found to evolve as
, with . Our results imply that only of present-day galaxies have undergone
major mergers since and that the average major merger rate is about Mpc
Gyr for . When dividing the galaxies into blue and red colors, the evolution index
remains similar for blue-blue pairs while becomes negative for red galaxies. The evolution trend for different
types of galaxies can be explained by the change of galaxy number density and clustering properties over cosmic
time. At fixed stellar mass (sm) the median infrared luminosity (lir) among merging galaxies and close pairs of
blue galaxies is twice (1.90.4) that of control pairs drawn from isolated blue galaxies. Enhancement declines
with galaxy separation, being strongest in close pairs and mergers and weaker in wide pairs compared to the control
sample. At , of massive interacting galaxies (sm > ) are found to be ULIRGs, compared to in the control sample. The large spread of speir
among interacting galaxies suggests that this enhancement may depend on the merger stage as well as other as yet
unidentified factors (e.g., galaxy structure, mass ratio, orbital characteristics, presence of AGN or bar). The
contribution of interacting systems to the total IR luminosity density is moderate ().1 INTRODUCTION 12
2 THE DEEP2 GALAXY REDSHIFT SURVEY: EVOLUTIONOF CLOSE
GALAXY PAIRS AND MAJOR-MERGER RATES UP TO z ~ 1.2 23
2.1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
2.2 DATA AND SELECTION FUNCTIONS . . . . . . . . . . . . . . . . . . . 25
2.3 PAIR STATISTICS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
2.4 MAJOR MERGER RATES . . . . . . . . . . . . . . . . . . . . . . . . . . 28
2.5 DISCUSSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
3 AEGIS: ENHANCEMENT OF DUST ENSHROUDED STAR FOR-
MATION IN CLOSE GALAXY PAIRS AND MERGING GALAXIES
UP TO z ~ 1 37
3.1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
3.2 DATA, SAMPLE SELECTIONS, AND METHODS . . . . . . . . . . . . 39
3.2.1 Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
3.2.2 Selection of Kinematic Pairs, Merging Galaxies, and Control Samples 40
3.2.3 Stellar Mass and Total IR Luminosity . . . . . . . . . . . . . . . . 41
3.3 RESULTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
3.4 DISCUSSION AND CONCLUSION . . . . . . . . . . . . . . . . . . . . . 43
4 THE EVOLUTION OF GALAXY PAIR COUNT FOR BLUE AND RED GALAXIES 51
4.1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
4.2 DATA DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
4.2.1 DEEP2 Spectroscopy and Photometry . . . . . . . . . . . . . . . . 52
4.2.2 CFHT MEGACAM i' and z' data . . . . . . . . . . . . . . . . . . 53
4.2.3 Final Sample Selection . . . . . . . . . . . . . . . . . . . . . . . . . 57
4.2.4 K-Correction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
4.2.5 Selection Function . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
4.3 RESULTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
4.3.1 Total Sample . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
4.3.2 Blue Galaxies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
4.3.3 Red Galaxies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
4.4 DISCUSSION AND CONCLUSION . . . . . . . . . . . . . . . . . . . . . 62
5 CONCLUSION 10
What Drives Galaxy Quenching? Resolving Molecular Gas and Star Formation in the Green Valley
Full text linkWe study quenching in seven green valley galaxies on kpc scales by resolving their molecular gas content using \textsuperscript{12}CO(1-0) observations obtained with NOEMA and ALMA, and their star-formation rate using spatially resolved optical spectroscopy from the MaNGA survey. We perform radial stacking of both datasets to increase the sensitivity to molecular gas and star formation, thereby avoiding biases against strongly quenched regions. We find that both spatially resolved gas fraction () and star formation efficiency () are responsible for quenching green valley galaxies at all radii: both quantities are suppressed with respect to typical star-forming regions. and have roughly equal influence in quenching the outer disc. We are, however, unable to identify the dominant mechanism in the strongly quenched central regions. We find that is reduced by in the central regions, but the star formation rate is too low to be measured, leading to upper limits for the . Moving from the outer disc to central regions, the reduction in is driven by an increasing profile rather than a decreasing profile. The reduced may therefore be caused by a decrease in the gas supply rather than molecular gas ejection mechanisms, such as winds driven by active galactic nuclei. We warn
more generally that studies investigating may be deceiving in inferring the cause of quenching, particularly in the central (bulge-dominated) regions of galaxies
The relative abundance of compact and normal massive early-type galaxies and its evolution from redshift z â1⁄4 2 to the present
No full textTHE DEEP2 GALAXY REDSHIFT SURVEY: EVOLUTION OF CLOSE GALAXY PAIRS and MAJOR-MERGER RATES UP TO z ∼ 1.21
No full textWe derive the close, kinematic pair fraction and merger rate up to redshift z ∼ 1.2 from the initial data of the
DEEP2 Redshift Survey. Assuming a mild luminosity evolution, the number of companions per luminous galaxy
is found to evolve as (1 z)m, with m p 0.51 0.28; assuming no evolution, m p 1.60 0.29. Our results
imply that only 9% of present-dayL∗ galaxies have undergone major mergers sincez∼ 1.2 and that the average
major merger rate is about 4#10 4h3 Mpc 3 Gyr 1 forz∼ 0.5–1.2. Most previous studies have yielded higher
values
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