THE EVOLUTIONARY HISTORY OF LYMAN BREAK GALAXIES BETWEEN REDSHIFT 4 AND 6: OBSERVING SUCCESSIVE GENERATIONS OF MASSIVE GALAXIES IN FORMATION

By D. Stark, Richard S. Ellis, A. Bunker, K. Bundy, Thomas Targett, A. Benson, M. Lacy. 2009

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We present new measurements of the evolution in the Lyman break galaxy (LBG) population between z ≃ 4 and z ≃ 6. By utilizing the extensive multiwavelength data sets available in the GOODS fields, we identify 2443 B, 506 V, and 137 i′-band dropout galaxies likely to be at z ≈ 4, 5, and 6. For the subset of dropouts for which reliable Spitzer IRAC photometry is feasible (roughly 35% of the sample), we estimate luminosity-weighted ages and stellar masses. With the goal of understanding the duration of typical star formation episodes in galaxies at z ≳ 4, we examine the distribution of stellar masses and ages as a function of cosmic time. We find that at a fixed rest-UV luminosity, the average stellar masses and ages of galaxies do not increase significantly between z ≃ 6 and 4. In order to maintain this near equilibrium in the average properties of high-redshift LBGs, we argue that there must be a steady flux of young, newly luminous objects at each successive redshift. When considered along with the short duty cycles inferred from clustering measurements, these results may suggest that galaxies are undergoing star formation episodes lasting only several hundred million years. In contrast to the unchanging relationship between the average stellar mass and rest-UV luminosity, we find that the number density of massive galaxies increases considerably with time over 4 ≲ z ≲ 6. Given this rapid increase of UV luminous massive galaxies, we explore the possibility that a significant fraction of massive (1011 M☉) z ≃ 2–3 distant red galaxies (DRGs) were in part assembled in an LBG phase at earlier times. Integrating the growth in the stellar mass function of actively forming LBGs over 4 ≲ z ≲ 6 down to z ≃ 2, we find that z ≳ 3 LBGs could have contributed significantly to the quiescent DRG population, indicating that the intense star-forming systems probed by submillimeter observations are not the only route toward the assembly of DRGs at z ≃ 2.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/6037ce956b3571cd326790c2d8e5e76d0c9acf35

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Citations in the corpus

• On the impact of empirical and theoretical star formation laws on galaxy formation (2010, background): “The slope of the observed relation seems to be constant over the redshift range probed, while the zero-point evolves strongly from z ≈ 0 to ∼4 (Daddi et al. 2007; Elbaz et al. 2007; Pérez-González et al. 2008), but appears roughly constant for 4 z 6 (Stark et al. 2009).”
• UV CONTINUUM SLOPE AND DUST OBSCURATION FROM z ∼ 6 TO z ∼ 2: THE STAR FORMATION RATE DENSITY AT HIGH REDSHIFT (2009, background): “Despite this sensitivity of β to age, no significant change are found in the median ages of star-forming galaxies from z ∼ 6 to z ∼ 4 (Stark et al. 2009), and little changes are found in the median ages as a function of luminosity (there is a hint that lower luminosity galaxies may be ∼1.5×…”
• The Star Formation Main Sequence in the Hubble Space Telescope Frontier Fields (2017, background): “…the sSFR increased steeply from z ∼ 0 to z ∼ 2 (e.g. Noeske et al. 2007; Santini et al. 2009; Karim et al. 2011) and flattened at higher redshift (e.g. Stark et al. 2009; González et al. 2010; Reddy et al. 2012; González et al. 2010; Labbé et al. 2010; McLure et al. 2011), in sharp contrast…”
• GOODS-HERSCHEL: STAR FORMATION, DUST ATTENUATION, AND THE FIR–RADIO CORRELATION ON THE MAIN SEQUENCE OF STAR-FORMING GALAXIES UP TO z ≃ 4 (2014, methodology): “Intriguingly enough, this underprediction of SFR conspire to create a plateau of the UV derived SSFR values atz ≥ 2 which was indeed observed in previous studies (see, e.g., Daddi et al. 2009; Stark et al. 2009; González et al. 2010).”
• THE MOST LUMINOUS z ∼ 9–10 GALAXY CANDIDATES YET FOUND: THE LUMINOSITY FUNCTION, COSMIC STAR-FORMATION RATE, AND THE FIRST MASS DENSITY ESTIMATE AT 500 Myr (2013, result): “However, they all lie higher than 2 Gyr−1, where a possible flattening of the SSFR had been suggested at z ∼ 3–6 (Stark et al. 2009; González et al. 2010), contrary to expectations from models.”
• THE RELATION BETWEEN STAR FORMATION RATE AND STELLAR MASS FOR GALAXIES AT 3.5 ⩽ z ⩽ 6.5 IN CANDELS (2014, background): “…properties such as stellar mass (M⋆) and star-formation rate (SFR) (Sawicki & Yee 1998; Papovich et al. 2001; Shapley et al. 2001; Giavalisco 2002; Stark et al. 2009; Förster Schreiber et al. 2004; Drory et al. 2004; Labbé et al. 2006; Maraston et al. 2010; Walcher et al. 2011; Curtis-Lake et…”
• Introducing the Illustris Project: the evolution of galaxy populations across cosmic time (2014, result): “It is worth noting that the measurements for these low masses at high redshifts are taken from González et al. (2011b), whose mass function for the more massive galaxies (M∗ 109 M ) is systematically lower than other measurements at z ∼ 4 [e.g. Stark et al. (2009) that is shown here].”
• THE AVERAGE STAR FORMATION HISTORIES OF GALAXIES IN DARK MATTER HALOS FROM z = 0–8 (2012, methodology): “If galaxies have bursty star formation, or if some fraction of star forming galaxies have extreme quantities of dust, then not all galaxies will be detected in Lyman break surveys (see also Stark et al. 2009; Lee et al. 2009).”
• THE CHARACTERISTIC STAR FORMATION HISTORIES OF GALAXIES AT REDSHIFTS z ∼ 2–7 (2012, background): “…of those emission lines may potentially result in a stronger evolution of specific SFR than has been found in other studies of z & 4 galaxies (Stark et al. 2009; González et al. 2010; Bouwens et al. 2011a), and may partially resolve the discrepancies between current observations and…”
• THE GALAXY LUMINOSITY FUNCTION DURING THE REIONIZATION EPOCH (2010, methodology): “From the L(Mh) relation, combined with the measure of the total stellar mass in z = 6 galaxies based on SED fits (Stark et al. 2009; Gonzalez et al. 2010; Labbé et al. 2009), we derive a typical star formation efficiency η(Mh = 10 11M⊙) ∼ 0.06 (6% of gas converted into stars) with a large…”
• EVIDENCE FOR UBIQUITOUS HIGH-EQUIVALENT-WIDTH NEBULAR EMISSION IN z ∼ 7 GALAXIES: TOWARD A CLEAN MEASUREMENT OF THE SPECIFIC STAR-FORMATION RATE USING A SAMPLE OF BRIGHT, MAGNIFIED GALAXIES (2013, background): “Initial observational studies found little evolution in the sSFR from z ∼ 2 to higher redshift in apparent disagreement with theories of star formation fueled by cold accretion (Stark et al. 2009; Gonzalez et al. 2010; Labbe et al. 2010a,b).”
• Galaxies at z = 6 - 9 from the WFC3/IR imaging of the HUDF (2009, background): “…action is clearly required at higher redshifts to commence and maintain reionisation, and extensive star-formation atz > 7 is implied by the stellar masses of galaxies atz ≃ 6 (Stark et al. 2009) and by reports of Balmer breaks in their spectral energy distribu ions (SEDs) (Eyles et al. 2007).”
• Star formation rates and masses of z∼ 2 galaxies from multicolour photometry (2010, background): “Obviously, the effect is especially strong for exponentially increasing SFRs. Incidentally, we note that exponentially decreasing SFRs have been assumed also for galaxies at very high redshifts (e.g., z = 4 − 6; Stark et al. 2009).”
• THE SPECTRAL ENERGY DISTRIBUTIONS OF z ∼ 8 GALAXIES FROM THE IRAC ULTRA DEEP FIELDS: EMISSION LINES, STELLAR MASSES, AND SPECIFIC STAR FORMATION RATES AT 650 MYR (2012, methodology): “This has been taken as evidence of substantial stellar masses ∼ 109 − 1010M⊙ (Eyles et al. 2005; Yan et al. 2006; Stark et al. 2009) and stellar ages (> 300Myr) (Labbé et al. 2006; González et al. 2010; 1 Based on observations made with the NASA/ESA Hubble Space Telescope, which is operated by…”
• EVOLUTION OF GALAXY STELLAR MASS FUNCTIONS, MASS DENSITIES, AND MASS-TO-LIGHT RATIOS FROM z ∼ 7 TO z ∼ 4 (2010, methodology): “…observed star formation rate (SFR) and stellar mass (Stark et al. 2009; Labbé et al. 2010a,b), with little apparent evolution between z ∼ 3 and z ∼ 7 (Stark et al. 2009; González et al. 2010), suggests an epoch of exponential growth which, interestingly, is similar to that found in simulations…”
• The galaxy stellar mass function at 3.5 ≤z ≤ 7.5 in the CANDELS/UDS, GOODS-South, and HUDF fields (2015, methodology): “Meanwhile, bluer selection bands were used by Stark et al. (2009) and Lee et al. (2012) who undertook their primary galaxy selection in the i775 and z850 ACS bands respectively (sampling the UV rest-frame wavelengths at z ≥ 4).”