Ultraviolet to Mid-Infrared Observations of Star-forming Galaxies at z ~ 2: Stellar Masses and Stellar Populations

By A. Shapley, C. Steidel, D. Erb, Naveen A. Reddy, K. Adelberger, M. Pettini, Pauline Barmby, Jiasheng Huang. 2005

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We present the broadband UV through mid-infrared spectral energy distributions (SEDs) of a sample of 72 spectroscopically confirmed star-forming galaxies at z = 2.30 ± 0.3. Located in a 72 arcmin2 field centered on the bright background QSO, HS 1700+643, these galaxies were preselected to lie at z ~ 2 solely on the basis of their rest-frame UV colors and luminosities and should be representative of UV-selected samples at high redshift. In addition to deep ground-based photometry spanning from 0.35 to 2.15 μm, we make use of Spitzer IRAC data, which probe the rest-frame near-IR at z ~ 2. The range of stellar populations present in the sample is investigated with simple, single-component stellar population synthesis models. The inability to constrain the form of the star formation history limits our ability to determine the parameters of extinction, age, and star formation rate without using external multiwavelength information. Emphasizing stellar mass estimates, which are much less affected by these uncertainties, we find ⟨log M*/M☉⟩ = 10.32 ± 0.51 for the sample. The addition of Spitzer IRAC data as a long-wavelength baseline reduces stellar mass uncertainties by a factor of 1.5-2 relative to estimates based on optical-Ks photometry alone. However, the total stellar mass estimated for the sample is remarkably insensitive to the inclusion of IRAC data. We find correlations between stellar mass and rest-frame R band (observed Ks) and rest-frame 1.4 μm (observed 4.5 μm) luminosities, although with significant scatter. Even at rest-frame 1.4 μm, the mass-to-light ratio varies by a factor of 15 indicating that even the rest-frame near-IR, when taken alone, is a poor indicator of stellar mass in star-forming galaxies at z ~ 2. Allowing for the possibility of episodic star formation, we find that typical galaxies in our sample could contain up to 3 times more stellar mass in an old underlying burst than what was inferred from single-component modeling. In contrast, mass estimates for the most massive galaxies in the sample (M* > 1011 M☉) are fairly insensitive to the method used to model the stellar population. Galaxies in this massive tail, which are also the oldest objects in the sample, could plausibly evolve into the passive galaxies discovered at z ~ 1.7 with near-IR selection techniques. In the general framework of hierarchical galaxy formation and mergers, which implies episodic star formation histories, galaxies at high redshift may pass in and out of UV-selected and near-IR color-selected samples as they evolve from phases of active star formation to quiescence and back again.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/322eef3162b83c12a603c0f4aa14073de6916258

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Citations in the corpus

Ultraviolet emission lines in young low-mass galaxies at z ≃ 2: physical properties and implications for studies at z > 7 (2014, methodology): “…an underlying very old stellar population are used in the SED fitting procedure,th inferred stellar masses of star formingz ≃ 2− 3 galaxies can be 3× larger than derived using single component star formation hstories (e.g., Papovich et al. 2001, Shapley et al. 2005, Dominguez et al. 2014, in prep).”
THE KILOPARSEC-SCALE KINEMATICS OF HIGH-REDSHIFT STAR-FORMING GALAXIES (2009, methodology): “As discussed by previous authors (e.g., Shapley et al. 2001, 2005a; Papovich et al. 2001) , degeneracies in the stellar population model tend to cancel out with regard to the total stellar mass, meaning that this is typically the best constrained of these parameters.”
Nebular Emission Line Ratios in z ≃ 2–3 Star-forming Galaxies with KBSS-MOSFIRE: Exploring the Impact of Ionization, Excitation, and Nitrogen-to-Oxygen Ratio (2016, background): “Still, early observations of small samples of high-redshift galaxies (e.g., Shapley et al. 2005; Erb et al. 2006a; Liu et al. 2008) suggested that the situation at high-z might be radically different, with galaxies exhibiting lower gas-phase oxygen abundance at fixed stellar mass and nebular line…”
A Spectroscopic Survey of Redshift 1.4 ≲ z ≲ 3.0 Galaxies in the GOODS-North Field: Survey Description, Catalogs, and Properties (2006, methodology): “This mean stellar mass is a factor of 2 lower than found in Shapley et al. (2005) and Erb et al. (2006c) partly because we included galaxies undetected toKs ¼ 24:1 in the sample considered here (as long as they had IRAC data to constrain the stellar mass), and these faint Ks galaxies on average…”
Resolved Galaxies in the Hubble Ultra Deep Field: Star Formation in Disks at High Redshift (2007, background): “…consistent with observations by Reddy et al. (2006a), who found a wide range of star formation ages for galaxies of various sizes at z 2, with van Dokkum et al. (2006), who found the same for massive galaxies, and with Shapley et al. (2005), who considered episodic star formation in z 2 galaxies.”
Submillimeter Galaxies at z ~ 2: Evidence for Major Mergers and Constraints on Lifetimes, IMF, and CO-H2 Conversion Factor (2008, result): “For a given IMF, star formation history, and set of stellar tracks the stellar masses are constrained to between 20% and 50%, similar to other published work in this field (Shapley et al. 2001, 2005; Förster Schreiber et al. 2004; Borys et al. 2005; Erb et al. 2006b, 2006c; Papovich et al. 2007).”
ON THE STELLAR POPULATIONS AND EVOLUTION OF STAR-FORMING GALAXIES AT 6.3 < z ⩽ 8.6 (2009, methodology): “Figure 12 compares our observations to a number of studies from the literature, from 2≤ z ≤ 7 (Shapley et al. 2005; Reddy et al. 2006; Stark et al. 2009, all of which assumed a Salpeter IMF), and shows the evolution of the mass of an L∗ galaxy with redshift.”
The Stellar Mass Assembly of Galaxies from z = 0 to z = 4: Analysis of a Sample Selected in the Rest-Frame Near-Infrared with Spitzer (2007, background): “Still, mass-to-light ratios in the rest-frame NIR from galaxy to galaxy may still vary by factor of 6–15 (depending on the mean age of the stellar population, the presence of recent bursts, etc...; see, e.g., Bell & de Jong 2001, Shapley et al. 2005, or Labbé et al. 2005).”
A CANDELS–3D-HST SYNERGY: RESOLVED STAR FORMATION PATTERNS AT 0.7 < z < 1.5 (2013, background): “…Space Flight Center, Greenbelt, MD 20771, USA wavelength baselines, from the rest-frame UV to infrared, allowed inferences on the global stellar population properties such as stellar mass, age and star formation rate (SFR; Papovich et al. 2001; Förster Schreiber et al. 2004; Shapley et al. 2005).”
Probing the Coevolution of Supermassive Black Holes and Galaxies Using Gravitationally Lensed Quasar Hosts (2006, background): “On the other hand, most z ≃ 2 galaxies have M/LR ≃ 0.5, and only the reddest galaxies reach M/LR ≃ 2 whether due to dust or age (Shapley et al. 2005).”
From Rings to Bulges: Evidence for Rapid Secular Galaxy Evolution at z ~ 2 from Integral Field Spectroscopy in the SINS Survey (2008, background): “These selection criteria sample fairly luminous (L 1011Y1012:5 L ) galaxies with star formation rates of 10Y300 M yr 1, with a range of ages 10 Myr-3 Gyr and stellar masses M 109Y1011:5 M (Shapley et al. 2005; Förster Schreiber et al. 2004; Erb et al. 2006b, 2006c; Daddi et al. 2004a, 2004b).”
VERY STRONG EMISSION-LINE GALAXIES IN THE WFC3 INFRARED SPECTROSCOPIC PARALLEL SURVEY AND IMPLICATIONS FOR HIGH-REDSHIFT GALAXIES, (2011, methodology): “The techniques used for the selection of galaxies include mostly the optical or NIR colors and UV continuum (e.g. Steidel et al. 2004; Daddi et al. 2004; Papovich et al. 2006; Steidel et al. 1996; Shapley et al. 2005; Erb et al. 2006a; Schiminovich et al. 2007).”
BULGE GROWTH AND QUENCHING SINCE z = 2.5 IN CANDELS/3D-HST (2014, background): “However, we are here interested in the stellar mass, which, among SED-derived properties, is most robust against variations (and uncertainties) in model assumptions (e.g., Papovich et al. 2001; Shapley et al. 2005; Maraston et al. 2010).”
THE GASEOUS ENVIRONMENT OF HIGH-z GALAXIES: PRECISION MEASUREMENTS OF NEUTRAL HYDROGEN IN THE CIRCUMGALACTIC MEDIUM OF z ∼ 2–3 GALAXIES IN THE KECK BARYONIC STRUCTURE SURVEY (2012, background): “The luminous parts of the galaxies are dominated by baryons, typically half stars and half cold gas (Shapley et al. 2005; Erb et al. 2006c), with half-light radii of∼ 2 pkpc (Law et al. 2011).”
A DEEP HUBBLE SPACE TELESCOPE SEARCH FOR ESCAPING LYMAN CONTINUUM FLUX AT z ∼ 1.3: EVIDENCE FOR AN EVOLVING IONIZING EMISSIVITY (2010, result): “In Figure 7, we compare our best-fit parameters to those of a sample of 72 LBGs of Shapley et al. (2005).”
Modeling the Panchromatic Spectral Energy Distributions of Galaxies (2013, methodology): “…to result in underestimated stellar masses when single-component SFH models are used (e.g., Papovich, Dickinson & Ferguson 2001; Daddi et al. 2004; Shapley et al. 2005; Lee et al. 2009b; Pforr, Maraston & Tonini 2012), but its effect on recovered SFRs and ages remained relatively less…”
A CENSUS OF STAR-FORMING GALAXIES IN THE Z ∼ 9–10 UNIVERSE BASED ON HST+SPITZER OBSERVATIONS OVER 19 CLASH CLUSTERS: THREE CANDIDATE Z ∼ 9–10 GALAXIES AND IMPROVED CONSTRAINTS ON THE STAR FORMATION RATE DENSITY AT Z ∼ 9.2 (2012, methodology): “Fortunately, there are well-established procedures to use the positions and spatial profiles of sources in available HST observations to model the IRAC image observations and extract fluxes (e.g., Shapley et al. 2005; Labbé et al. 2006; Grazian et al. 2006; Laidler et al. 2007).”