GAS FRACTION AND DEPLETION TIME OF MASSIVE STAR-FORMING GALAXIES AT z ∼ 3.2: NO CHANGE IN GLOBAL STAR FORMATION PROCESS OUT TO z > 3

Abstract

The observed evolution of the gas fraction and its associated depletion time in main-sequence (MS) galaxies provides insights on how star formation proceeds over cosmic time. We report ALMA detections of the rest-frame ∼300 μm continuum observed at 240 GHz for 45 massive (), i.e., MS, galaxies at » z 3.2 in the COSMOS field. From an empirical calibration between cold neutral, i.e., molecular and atomic, gas mass M gas and monochromatic (rest-frame) infrared luminosity, the gas mass for this sample is derived. Combined with stellar mass  M and star formation rate (SFR) estimates (from MAGPHYS fits) we obtain a median gas fraction of Our results are fully consistent with the expected flattening of the redshift evolution from the 2-SFM (2 star formation mode) framework which empirically prescribes the evolution assuming a universal, log-linear relation between SFR and gas mass coupled to the redshift evolution of the specific star formation rate (sSFR) of MS galaxies. While t depl. shows only a mild dependence on location within the MS, a clear trend of increasing m gas across the MS is observed (as known from previous studies). Further, we comment on trends within the MS and (in)consistencies with other studies.

A Radio-to-mm Census of Star-forming Galaxies in Protocluster 4C23.56 at Z = 2.5: Gas Mass and Its Fraction Revealed with ALMA

“…By restricting galaxies in PHIBBS-I, which results in only sevengalaxies for comparison, we find that the average gas fraction does not differ (á ñ -f gas,PHIBBS I,MS =0.49±0.05;bottom of Figure 10). Other studies on the main-sequence galaxies have revealed similar results (e.g., Magdis et al 2012;Saintonge et al 2013;Sargent et al 2014;Scoville et al 2014;S16;Schinnerer et al 2016). ALESS SMGs on the massive main sequence at < < z 2 3 (total number of 13) appear to have a slightly higher mean value (á ñ f gas =0.64±0.07; Figure 10 top) but is nevertheless consistent within an error.…”

“…With the advent of large surveys revealing the gas content of star-forming galaxies, the evolution of sSFR appears to be caused by the higher gas fraction ( star, at least on the main sequence. Furthermore, the higher M gas appears to mimic the higher gas supply rate (e.g., Magdis et al 2012;Saintonge et al 2013;Tacconi et al 2013;Sargent et al 2014;Genzel et al 2015, hereafter G15;Scoville et al 2014Scoville et al , 2016Scoville et al , hereafter S16, 2017Schinnerer et al 2016). …”

The Strong Gravitationally Lensed Herschel Galaxy HLock01: Optical Spectroscopy Reveals a Close Galaxy Merger with Evidence of Inflowing Gas

“…Our new analysis reveals a large, highly obscured stellar mass, similar to the most massive and extreme SMGs during the peak of star formation (e.g., Hainline et al 2011;Ma et al 2015;Schinnerer et al 2016;Miettinen et al 2017;Nayyeri et al 2017). However, as already discussed in Conley et al (2011) andWardlow et al (2013), HLock01-R has a moderately low q IR =1.8±0.4 (which is the logarithmic ratio of L IR and the rest-frame 1.4 GHz flux density), compared with the mean value for HerMES sources (q IR =2.40±0.12; Ivison et al 2010a).…”

Dust and gas in star-forming galaxies at z ~ 3

“…Also, Scoville et al (2017) and Schinnerer et al (2016), were able to place constraints on the gas masses of individual galaxies up to z = 4, using single band measurements of the dust emission flux on the Rayleigh-Jeans side of their SED. Finally, Magdis et al (2012a), and Tan et al (2014), presented CO observations, and therefore M H 2 estimates for a couple of z = 3 − 4 Lyman Break Galaxies (LBGs).…”