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Title: DISCOVERY OF MASSIVE, MOSTLY STAR FORMATION QUENCHED GALAXIES WITH EXTREMELY LARGE Lyα EQUIVALENT WIDTHS AT z ∼ 3

Abstract

We report a discovery of six massive galaxies with both extremely large Lyα equivalent widths (EWs) and evolved stellar populations at z ∼ 3. These MAssive Extremely STrong Lyα emitting Objects (MAESTLOs) have been discovered in our large-volume systematic survey for strong Lyα emitters (LAEs) with 12 optical intermediate-band data taken with Subaru/Suprime-Cam in the COSMOS field. Based on the spectral energy distribution fitting analysis for these LAEs, it is found that these MAESTLOs have (1) large rest-frame EWs of EW{sub 0} (Lyα) ∼ 100–300 Å, (2) M{sub ⋆} ∼ 10{sup 10.5}–10{sup 11.1} M{sub ⊙}, and (3) relatively low specific star formation rates of SFR/M{sub ⋆} ∼ 0.03–1 Gyr{sup −1}. Three of the six MAESTLOs have extended Lyα emission with a radius of several kiloparsecs, although they show very compact morphology in the HST/ACS images, which correspond to the rest-frame UV continuum. Since the MAESTLOs do not show any evidence for active galactic nuclei, the observed extended Lyα emission is likely to be caused by a star formation process including the superwind activity. We suggest that this new class of LAEs, MAESTLOs, provides a missing link from star-forming to passively evolving galaxies at the peak era of the cosmic starmore » formation history.« less

Authors:
; ; ; ;  [1]; ;  [2];  [3];  [4];  [5];  [6]; ; ;  [7];  [8];  [9]; ; ;  [10];  [11] more »; « less
  1. Research Center for Space and Cosmic Evolution, Ehime University, Bunkyo-cho, Matsuyama 790-8577 (Japan)
  2. Department of Astronomy, California Institute of Technology, MS 105-24, Pasadena, CA 91125 (United States)
  3. Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)
  4. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
  5. Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Mariesvej 30, DK-2100 Copenhagen (Denmark)
  6. Institut d’Astrophysique de Paris, UMR7095 CNRS, Université Pierre et Marie Curie, 98 bis Boulevard Arago, F-75014 Paris (France)
  7. Aix Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille), UMR 7326, F-13388 Marseille (France)
  8. National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States)
  9. Dipartimento di Astronomia, Universita di Padova, vicolo dell’Osservatorio 2, I-35122 Padua (Italy)
  10. Department of Physics, ETH Zurich, 8093 Zurich (Switzerland)
  11. MPI for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany)
Publication Date:
OSTI Identifier:
22518923
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 809; 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; COSMOLOGY; EMISSION SPECTRA; ENERGY SPECTRA; GALAXIES; GALAXY NUCLEI; IMAGES; LYMAN LINES; MORPHOLOGY; RED SHIFT; STAR EVOLUTION; STARS; UNIVERSE

Citation Formats

Taniguchi, Yoshiaki, Kajisawa, Masaru, Kobayashi, Masakazu A. R., Nagao, Tohru, Shioya, Yasuhiro, Scoville, Nick Z., Capak, Peter L., Sanders, David B., Koekemoer, Anton M., Toft, Sune, McCracken, Henry J., Le Fèvre, Olivier, Tasca, Lidia, Ilbert, Olivier, Sheth, Kartik, Renzini, Alvio, Lilly, Simon, Carollo, Marcella, Kovač, Katarina, Schinnerer, Eva, E-mail: tani@cosmos.phys.sci.ehime-u.ac.jp, and and others. DISCOVERY OF MASSIVE, MOSTLY STAR FORMATION QUENCHED GALAXIES WITH EXTREMELY LARGE Lyα EQUIVALENT WIDTHS AT z ∼ 3. United States: N. p., 2015. Web. doi:10.1088/2041-8205/809/1/L7.
Taniguchi, Yoshiaki, Kajisawa, Masaru, Kobayashi, Masakazu A. R., Nagao, Tohru, Shioya, Yasuhiro, Scoville, Nick Z., Capak, Peter L., Sanders, David B., Koekemoer, Anton M., Toft, Sune, McCracken, Henry J., Le Fèvre, Olivier, Tasca, Lidia, Ilbert, Olivier, Sheth, Kartik, Renzini, Alvio, Lilly, Simon, Carollo, Marcella, Kovač, Katarina, Schinnerer, Eva, E-mail: tani@cosmos.phys.sci.ehime-u.ac.jp, & and others. DISCOVERY OF MASSIVE, MOSTLY STAR FORMATION QUENCHED GALAXIES WITH EXTREMELY LARGE Lyα EQUIVALENT WIDTHS AT z ∼ 3. United States. doi:10.1088/2041-8205/809/1/L7.
Taniguchi, Yoshiaki, Kajisawa, Masaru, Kobayashi, Masakazu A. R., Nagao, Tohru, Shioya, Yasuhiro, Scoville, Nick Z., Capak, Peter L., Sanders, David B., Koekemoer, Anton M., Toft, Sune, McCracken, Henry J., Le Fèvre, Olivier, Tasca, Lidia, Ilbert, Olivier, Sheth, Kartik, Renzini, Alvio, Lilly, Simon, Carollo, Marcella, Kovač, Katarina, Schinnerer, Eva, E-mail: tani@cosmos.phys.sci.ehime-u.ac.jp, and and others. Mon . "DISCOVERY OF MASSIVE, MOSTLY STAR FORMATION QUENCHED GALAXIES WITH EXTREMELY LARGE Lyα EQUIVALENT WIDTHS AT z ∼ 3". United States. doi:10.1088/2041-8205/809/1/L7.
@article{osti_22518923,
title = {DISCOVERY OF MASSIVE, MOSTLY STAR FORMATION QUENCHED GALAXIES WITH EXTREMELY LARGE Lyα EQUIVALENT WIDTHS AT z ∼ 3},
author = {Taniguchi, Yoshiaki and Kajisawa, Masaru and Kobayashi, Masakazu A. R. and Nagao, Tohru and Shioya, Yasuhiro and Scoville, Nick Z. and Capak, Peter L. and Sanders, David B. and Koekemoer, Anton M. and Toft, Sune and McCracken, Henry J. and Le Fèvre, Olivier and Tasca, Lidia and Ilbert, Olivier and Sheth, Kartik and Renzini, Alvio and Lilly, Simon and Carollo, Marcella and Kovač, Katarina and Schinnerer, Eva, E-mail: tani@cosmos.phys.sci.ehime-u.ac.jp and and others},
abstractNote = {We report a discovery of six massive galaxies with both extremely large Lyα equivalent widths (EWs) and evolved stellar populations at z ∼ 3. These MAssive Extremely STrong Lyα emitting Objects (MAESTLOs) have been discovered in our large-volume systematic survey for strong Lyα emitters (LAEs) with 12 optical intermediate-band data taken with Subaru/Suprime-Cam in the COSMOS field. Based on the spectral energy distribution fitting analysis for these LAEs, it is found that these MAESTLOs have (1) large rest-frame EWs of EW{sub 0} (Lyα) ∼ 100–300 Å, (2) M{sub ⋆} ∼ 10{sup 10.5}–10{sup 11.1} M{sub ⊙}, and (3) relatively low specific star formation rates of SFR/M{sub ⋆} ∼ 0.03–1 Gyr{sup −1}. Three of the six MAESTLOs have extended Lyα emission with a radius of several kiloparsecs, although they show very compact morphology in the HST/ACS images, which correspond to the rest-frame UV continuum. Since the MAESTLOs do not show any evidence for active galactic nuclei, the observed extended Lyα emission is likely to be caused by a star formation process including the superwind activity. We suggest that this new class of LAEs, MAESTLOs, provides a missing link from star-forming to passively evolving galaxies at the peak era of the cosmic star formation history.},
doi = {10.1088/2041-8205/809/1/L7},
journal = {Astrophysical Journal Letters},
number = 1,
volume = 809,
place = {United States},
year = {Mon Aug 10 00:00:00 EDT 2015},
month = {Mon Aug 10 00:00:00 EDT 2015}
}
  • We study the statistical distribution of satellites around star-forming and quiescent central galaxies at 1 < z < 3 using imaging from the FourStar Galaxy Evolution Survey and the Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey. The deep near-IR data select satellites down to log (M/M {sub ☉}) > 9 at z < 3. The radial satellite distribution around centrals is consistent with a projected Navarro-Frenk-White profile. Massive quiescent centrals, log (M/M {sub ☉}) > 10.78, have ∼2 times the number of satellites compared to star-forming centrals with a significance of 2.7σ even after accounting for differences in the centrals'more » stellar-mass distributions. We find no statistical difference in the satellite distributions of intermediate-mass quiescent and star-forming centrals, 10.48 < log (M/M {sub ☉}) < 10.78. Compared to the Guo et al. semi-analytic model, the excess number of satellites indicates that quiescent centrals have halo masses 0.3 dex larger than star-forming centrals, even when the stellar-mass distributions are fixed. We use a simple toy model that relates halo mass and quenching, which roughly reproduces the observed quenched fractions and the differences in halo mass between star-forming and quenched galaxies only if galaxies have a quenching probability that increases with halo mass from ∼0 for log (M{sub h} /M {sub ☉}) ∼ 11 to ∼1 for log (M{sub h} /M {sub ☉}) ∼ 13.5. A single halo-mass quenching threshold is unable to reproduce the quiescent fraction and satellite distribution of centrals. Therefore, while halo quenching may be an important mechanism, it is unlikely to be the only factor driving quenching. It remains unclear why a high fraction of centrals remain star-forming even in relatively massive halos.« less
  • Growing observational evidence indicates that nebular line emission has a significant impact on the rest-frame optical fluxes of z ∼ 5-7 galaxies. This line emission makes z ∼ 5-7 galaxies appear more massive, with lower specific star-formation rates (sSFRs). However, corrections for this line emission have been difficult to perform reliably because of huge uncertainties on the strength of such emission at z ≳ 5.5. In this paper, we present the most direct observational evidence thus far for ubiquitous high-equivalent-width (EW) [O III] + Hβ line emission in Lyman-break galaxies at z ∼ 7, and we present a strategy formore » an improved measurement of the sSFR at z ∼ 7. We accomplish this through the selection of bright galaxies in the narrow redshift window z ∼ 6.6-7.0 where the Spitzer/Infrared Array Camera (IRAC) 4.5 μm flux provides a clean measurement of the stellar continuum light, in contrast with the 3.6 μm flux, which is contaminated by the prominent [O III] + Hβ lines. To ensure a high signal-to-noise ratio for our IRAC flux measurements, we consider only the brightest (H {sub 160} < 26 mag) magnified galaxies we have identified behind galaxy clusters. It is remarkable that the mean rest-frame optical color for our bright seven-source sample is very blue, [3.6]-[4.5] = –0.9 ± 0.3. Such blue colors cannot be explained by the stellar continuum light and require that the rest-frame EW of [O III] + Hβ is greater than 637 Å for the average source. The four bluest sources from our seven-source sample require an even more extreme EW of 1582 Å. We can also set a robust lower limit of ≳ 4 Gyr{sup –1} on the sSFR of our sample based on the mean spectral energy distribution.« less
  • We present Hubble Space Telescope NIC2 morphologies of a spectroscopic sample of massive galaxies at z approx 2.3 by extending our sample of 9 compact quiescent galaxies (r{sub e} approx 0.9 kpc) with 10 massive emission-line galaxies. The emission-line galaxies are classified by the nature of their ionized emission; there are six star-forming galaxies and four galaxies hosting an active galactic nucleus (AGN). The star-forming galaxies are the largest among the emission-line galaxies, with a median size of r{sub e} = 2.8 kpc. The three galaxies with the highest star formation rates (approx>100 M {sub sun} yr{sup -1}) have irregularmore » and clumpy morphologies. The AGN host galaxies are more similar to the compact quiescent galaxies in terms of their structures (r{sub e} approx 1.1 kpc) and spectral energy distributions. The total sample clearly separates into two classes in a color-mass diagram: the large star-forming galaxies that form the blue cloud, and the compact quiescent galaxies on the red sequence. However, it is unclear how or even if the two classes are evolutionary related. Three out of six massive star-forming galaxies have dense cores and thus may passively evolve into compact galaxies due to fading of outer star-forming regions. For these galaxies, a reverse scenario in which compact galaxies grow inside-out by star formation is also plausible. We do caution though that the sample is small. Nonetheless, it is evident that a Hubble sequence of massive galaxies with strongly correlated galaxy properties is already in place at z > 2.« less
  • We present an analysis of an H {sub 160}-selected photometric catalog of galaxies in the Hubble Ultra-Deep Field, using imaging from the WFC3/IR camera on the Hubble Space Telescope in combination with archival ultraviolet, optical, and near-infrared imaging. Using these data, we measure the spectral energy distributions of ∼1500 galaxies to a limiting H {sub 160} magnitude of 27.8, from which we fit photometric redshifts and stellar population estimates for all galaxies with well-determined Spitzer IRAC fluxes, allowing for the determination of the cumulative mass function within the range 1 < z < 6. By selecting samples of galaxies atmore » a constant cumulative number density, we are able to explore the coevolution of stellar masses and star formation rates (SFRs) for progenitor galaxies and their descendants from z ∼ 6. We find a steady increase in the SFRs of galaxies at constant number density from z ∼ 6 to z ∼ 3, accompanied by gradually declining specific star formation rates (sSFRs) during this same period. The peak epoch of star formation is also found to shift to later times for galaxies with increasing number densities, in agreement with the expectations from cosmic downsizing. The observed SFRs can fully account for the mass growth to z ∼ 2 among galaxies with cumulative number densities greater than 10{sup –3.5} Mpc{sup –3}. For galaxies with a lower constant number density (higher mean mass), we find the observed stellar masses are ∼three times greater than that which may be accounted for by the observed star formation alone at late times, implying that growth from mergers plays an important role at z < 2. We additionally observe a decreasing sSFR, equivalent to approximately one order of magnitude, from z ∼ 6 to z ∼ 2 among galaxies with number densities less than 10{sup –3.5} Mpc{sup –3}, along with significant evidence that at any redshift the sSFR is higher for galaxies at higher number density. The combination of these findings can qualitatively explain the previous findings of a specific star formation rate plateau at high redshift. Tracing the evolution of the fraction of quiescent galaxies for samples matched in cumulative number density over this redshift range, we find no unambiguous examples of quiescent galaxies at z > 4.« less
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