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Title: GEOMETRY OF STAR-FORMING GALAXIES FROM SDSS, 3D-HST, AND CANDELS

Abstract

We determine the intrinsic, three-dimensional shape distribution of star-forming galaxies at 0 < z < 2.5, as inferred from their observed projected axis ratios. In the present-day universe, star-forming galaxies of all masses 10{sup 9}-10{sup 11} M {sub ☉} are predominantly thin, nearly oblate disks, in line with previous studies. We now extend this to higher redshifts, and find that among massive galaxies (M {sub *} > 10{sup 10} M {sub ☉}) disks are the most common geometric shape at all z ≲ 2. Lower-mass galaxies at z > 1 possess a broad range of geometric shapes: the fraction of elongated (prolate) galaxies increases toward higher redshifts and lower masses. Galaxies with stellar mass 10{sup 9} M {sub ☉} (10{sup 10} M {sub ☉}) are a mix of roughly equal numbers of elongated and disk galaxies at z ∼ 1 (z ∼ 2). This suggests that galaxies in this mass range do not yet have disks that are sustained over many orbital periods, implying that galaxies with present-day stellar mass comparable to that of the Milky Way typically first formed such sustained stellar disks at redshift z ∼ 1.5-2. Combined with constraints on the evolution of the star formation ratemore » density and the distribution of star formation over galaxies with different masses, our findings imply that, averaged over cosmic time, the majority of stars formed in disks.« less

Authors:
; ; ;  [1];  [2]; ; ; ;  [3]; ; ;  [4];  [5];  [6];  [7]; ;  [8];  [9];  [10];  [11] more »; « less
  1. Max-Planck Institut für Astronomie, Königstuhl 17, D-69117, Heidelberg (Germany)
  2. Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109 (United States)
  3. UCO/Lick Observatory, Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States)
  4. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
  5. Astronomy Department, University of Massachusetts, Amherst, MA 01003 (United States)
  6. South African Astronomical Observatory, P.O. Box 9, Observatory 7935 (South Africa)
  7. Astrophysics Science Division, Goddard Space Center, Greenbelt, MD 20771 (United States)
  8. Department of Astronomy, Yale University, New Haven, CT 06511 (United States)
  9. Center for Astrophysics and Planetary Science, Racah Institute of Physics, The Hebrew University, Jerusalem 91904 (Israel)
  10. Department of Theoretical Physics, Universidad Autonoma de Madrid, E-28049 Madrid (Spain)
  11. Leiden Observatory, Leiden University, P.O. Box 9513, NL-2300 AA Leiden (Netherlands)
Publication Date:
OSTI Identifier:
22365222
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 792; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; COMPARATIVE EVALUATIONS; LIMITING VALUES; MASS; MILKY WAY; RED SHIFT; STAR EVOLUTION; STARS; THREE-DIMENSIONAL CALCULATIONS; UNIVERSE

Citation Formats

Van der Wel, A., Chang, Yu-Yen, Rix, H.-W., Martig, M., Bell, E. F., Holden, B. P., Koo, D. C., Mozena, M., Faber, S. M., Ferguson, H. C., Brammer, G., Kassin, S. A., Giavalisco, M., Skelton, R., Whitaker, K., Momcheva, I., Van Dokkum, P. G., Dekel, A., Ceverino, D., Franx, M., E-mail: vdwel@mpia.de, and and others. GEOMETRY OF STAR-FORMING GALAXIES FROM SDSS, 3D-HST, AND CANDELS. United States: N. p., 2014. Web. doi:10.1088/2041-8205/792/1/L6.
Van der Wel, A., Chang, Yu-Yen, Rix, H.-W., Martig, M., Bell, E. F., Holden, B. P., Koo, D. C., Mozena, M., Faber, S. M., Ferguson, H. C., Brammer, G., Kassin, S. A., Giavalisco, M., Skelton, R., Whitaker, K., Momcheva, I., Van Dokkum, P. G., Dekel, A., Ceverino, D., Franx, M., E-mail: vdwel@mpia.de, & and others. GEOMETRY OF STAR-FORMING GALAXIES FROM SDSS, 3D-HST, AND CANDELS. United States. doi:10.1088/2041-8205/792/1/L6.
Van der Wel, A., Chang, Yu-Yen, Rix, H.-W., Martig, M., Bell, E. F., Holden, B. P., Koo, D. C., Mozena, M., Faber, S. M., Ferguson, H. C., Brammer, G., Kassin, S. A., Giavalisco, M., Skelton, R., Whitaker, K., Momcheva, I., Van Dokkum, P. G., Dekel, A., Ceverino, D., Franx, M., E-mail: vdwel@mpia.de, and and others. Mon . "GEOMETRY OF STAR-FORMING GALAXIES FROM SDSS, 3D-HST, AND CANDELS". United States. doi:10.1088/2041-8205/792/1/L6.
@article{osti_22365222,
title = {GEOMETRY OF STAR-FORMING GALAXIES FROM SDSS, 3D-HST, AND CANDELS},
author = {Van der Wel, A. and Chang, Yu-Yen and Rix, H.-W. and Martig, M. and Bell, E. F. and Holden, B. P. and Koo, D. C. and Mozena, M. and Faber, S. M. and Ferguson, H. C. and Brammer, G. and Kassin, S. A. and Giavalisco, M. and Skelton, R. and Whitaker, K. and Momcheva, I. and Van Dokkum, P. G. and Dekel, A. and Ceverino, D. and Franx, M., E-mail: vdwel@mpia.de and and others},
abstractNote = {We determine the intrinsic, three-dimensional shape distribution of star-forming galaxies at 0 < z < 2.5, as inferred from their observed projected axis ratios. In the present-day universe, star-forming galaxies of all masses 10{sup 9}-10{sup 11} M {sub ☉} are predominantly thin, nearly oblate disks, in line with previous studies. We now extend this to higher redshifts, and find that among massive galaxies (M {sub *} > 10{sup 10} M {sub ☉}) disks are the most common geometric shape at all z ≲ 2. Lower-mass galaxies at z > 1 possess a broad range of geometric shapes: the fraction of elongated (prolate) galaxies increases toward higher redshifts and lower masses. Galaxies with stellar mass 10{sup 9} M {sub ☉} (10{sup 10} M {sub ☉}) are a mix of roughly equal numbers of elongated and disk galaxies at z ∼ 1 (z ∼ 2). This suggests that galaxies in this mass range do not yet have disks that are sustained over many orbital periods, implying that galaxies with present-day stellar mass comparable to that of the Milky Way typically first formed such sustained stellar disks at redshift z ∼ 1.5-2. Combined with constraints on the evolution of the star formation rate density and the distribution of star formation over galaxies with different masses, our findings imply that, averaged over cosmic time, the majority of stars formed in disks.},
doi = {10.1088/2041-8205/792/1/L6},
journal = {Astrophysical Journal Letters},
number = 1,
volume = 792,
place = {United States},
year = {Mon Sep 01 00:00:00 EDT 2014},
month = {Mon Sep 01 00:00:00 EDT 2014}
}
  • The nature of dust in distant galaxies is not well understood, and until recently few direct dust measurements have been possible. We investigate dust in distant star-forming galaxies using near-infrared grism spectra of the 3D-HST survey combined with archival multi-wavelength photometry. These data allow us to make a direct comparison between dust around star-forming regions (A {sub V,} {sub H} {sub II}) and the integrated dust content (A {sub V,} {sub star}). We select a sample of 163 galaxies between 1.36 ≤ z ≤ 1.5 with Hα signal-to-noise ratio ≥5 and measure Balmer decrements from stacked spectra to calculate Amore » {sub V,} {sub H} {sub II}. First, we stack spectra in bins of A {sub V,} {sub star}, and find that A {sub V,} {sub H} {sub II} = 1.86 A {sub V,} {sub star}, with a significance of σ = 1.7. Our result is consistent with the two-component dust model, in which galaxies contain both diffuse and stellar birth cloud dust. Next, we stack spectra in bins of specific star formation rate (log SSFR), star formation rate (log SFR), and stellar mass (log M {sub *}). We find that on average A {sub V,} {sub H} {sub II} increases with SFR and mass, but decreases with increasing SSFR. Interestingly, the data hint that the amount of extra attenuation decreases with increasing SSFR. This trend is expected from the two-component model, as the extra attenuation will increase once older stars outside the star-forming regions become more dominant in the galaxy spectrum. Finally, using Balmer decrements we derive dust-corrected Hα SFRs, and find that stellar population modeling produces incorrect SFRs if rapidly declining star formation histories are included in the explored parameter space.« less
  • The dense interiors of massive galaxies are among the most intriguing environments in the universe. In this paper,we ask when these dense cores were formed and determine how galaxies gradually assembled around them. We select galaxies that have a stellar mass >3 × 10{sup 10} M{sub ☉} inside r = 1 kpc out to z = 2.5, using the 3D-HST survey and data at low redshift. Remarkably, the number density of galaxies with dense cores appears to have decreased from z = 2.5 to the present. This decrease is probably mostly due to stellar mass loss and the resulting adiabaticmore » expansion, with some contribution from merging. We infer that dense cores were mostly formed at z > 2.5, consistent with their largely quiescent stellar populations. While the cores appear to form early, the galaxies in which they reside show strong evolution: their total masses increase by a factor of 2-3 from z = 2.5 to z = 0 and their effective radii increase by a factor of 5-6. As a result, the contribution of dense cores to the total mass of the galaxies in which they reside decreases from ∼50% at z = 2.5 to ∼15% at z = 0. Because of their early formation, the contribution of dense cores to the total stellar mass budget of the universe is a strong function of redshift. The stars in cores with M{sub 1{sub kpc}} > 3 × 10{sup 10} M{sub ☉} make up ∼0.1% of the stellar mass density of the universe today but 10%-20% at z ∼ 2, depending on their initial mass function. The formation of these cores required the conversion of ∼10{sup 11} M{sub ☉} of gas into stars within ∼1 kpc, while preventing significant star formation at larger radii.« less
  • We investigate the buildup of galaxies at z {approx} 1 using maps of H{alpha} and stellar continuum emission for a sample of 57 galaxies with rest-frame H{alpha} equivalent widths >100 A in the 3D-HST grism survey. We find that the H{alpha} emission broadly follows the rest-frame R-band light but that it is typically somewhat more extended and clumpy. We quantify the spatial distribution with the half-light radius. The median H{alpha} effective radius r{sub e} (H{alpha}) is 4.2 {+-} 0.1 kpc but the sizes span a large range, from compact objects with r{sub e} (H{alpha}) {approx} 1.0 kpc to extended disksmore » with r{sub e} (H{alpha}) {approx} 15 kpc. Comparing H{alpha} sizes to continuum sizes, we find =1.3 {+-} 0.1 for the full sample. That is, star formation, as traced by H{alpha}, typically occurs out to larger radii than the rest-frame R-band stellar continuum; galaxies are growing their radii and building up from the inside out. This effect appears to be somewhat more pronounced for the largest galaxies. Using the measured H{alpha} sizes, we derive star formation rate surface densities, {Sigma}{sub SFR}. We find that {Sigma}{sub SFR} ranges from {approx}0.05 M{sub Sun} yr{sup -1} kpc{sup -2} for the largest galaxies to {approx}5 M{sub Sun} yr{sup -1} kpc{sup -2} for the smallest galaxies, implying a large range in physical conditions in rapidly star-forming z {approx} 1 galaxies. Finally, we infer that all galaxies in the sample have very high gas mass fractions and stellar mass doubling times <500 Myr. Although other explanations are also possible, a straightforward interpretation is that we are simultaneously witnessing the rapid formation of compact bulges and large disks at z {approx} 1.« less
  • We use HST/WFC3 imaging from the CANDELS Multi-Cycle Treasury Survey, in conjunction with the Sloan Digital Sky Survey, to explore the evolution of galactic structure for galaxies with stellar masses >3 Multiplication-Sign 10{sup 10} M{sub Sun} from z = 2.2 to the present epoch, a time span of 10 Gyr. We explore the relationship between rest-frame optical color, stellar mass, star formation activity, and galaxy structure. We confirm the dramatic increase from z = 2.2 to the present day in the number density of non-star-forming galaxies above 3 Multiplication-Sign 10{sup 10} M{sub Sun} reported by others. We further find thatmore » the vast majority of these quiescent systems have concentrated light profiles, as parameterized by the Sersic index, and the population of concentrated galaxies grows similarly rapidly. We examine the joint distribution of star formation activity, Sersic index, stellar mass, inferred velocity dispersion, and stellar surface density. Quiescence correlates poorly with stellar mass at all z < 2.2. Quiescence correlates well with Sersic index at all redshifts. Quiescence correlates well with 'velocity dispersion' and stellar surface density at z > 1.3, and somewhat less well at lower redshifts. Yet, there is significant scatter between quiescence and galaxy structure: while the vast majority of quiescent galaxies have prominent bulges, many of them have significant disks, and a number of bulge-dominated galaxies have significant star formation. Noting the rarity of quiescent galaxies without prominent bulges, we argue that a prominent bulge (and perhaps, by association, a supermassive black hole) is an important condition for quenching star formation on galactic scales over the last 10 Gyr, in qualitative agreement with the active galactic nucleus feedback paradigm.« less
  • Ultra-deep Advanced Camera for Surveys (ACS) and WFC3/IR HUDF+HUDF09 data, along with the wide-area GOODS+ERS+CANDELS data over the CDF-S GOODS field, are used to measure UV colors, expressed as the UV-continuum slope {beta}, of star-forming galaxies over a wide range of luminosity (0.1L*{sub z=3} to 2L*{sub z=3}) at high redshift (z {approx} 7 to z {approx} 4). {beta} is measured using all ACS and WFC3/IR passbands uncontaminated by Ly{alpha} and spectral breaks. Extensive tests show that our {beta} measurements are only subject to minimal biases. Using a different selection procedure, Dunlop et al. recently found large biases in their {beta}more » measurements. To reconcile these different results, we simulated both approaches and found that {beta} measurements for faint sources are subject to large biases if the same passbands are used both to select the sources and to measure {beta}. High-redshift galaxies show a well-defined rest-frame UV color-magnitude (CM) relationship that becomes systematically bluer toward fainter UV luminosities. No evolution is seen in the slope of the UV CM relationship in the first 1.5 Gyr, though there is a small evolution in the zero point to redder colors from z {approx} 7 to z {approx} 4. This suggests that galaxies are evolving along a well-defined sequence in the L{sub UV}-color ({beta}) plane (a 'star-forming sequence'?). Dust appears to be the principal factor driving changes in the UV color {beta} with luminosity. These new larger {beta} samples lead to improved dust extinction estimates at z {approx} 4-7 and confirm that the extinction is essentially zero at low luminosities and high redshifts. Inclusion of the new dust extinction results leads to (1) excellent agreement between the star formation rate (SFR) density at z {approx} 4-8 and that inferred from the stellar mass density; and (2) to higher specific star formation rates (SSFRs) at z {approx}> 4, suggesting that the SSFR may evolve modestly (by factors of {approx}2) from z {approx} 4-7 to z {approx} 2.« less