A TURNOVER IN THE GALAXY MAIN SEQUENCE OF STAR FORMATION ATM_*∼ 10¹⁰M_☉FOR REDSHIFTSz< 1.3

Abstract

The relationship between galaxy star formation rates (SFR) and stellar masses (M * ) is re-examined using a mass-selected sample of ∼62,000 star-forming galaxies at z ≤ 1.3 in the COSMOS 2-deg 2 field. Using new far-infrared photometry from Herschel-PACS and SPIRE and Spitzer-MIPS 24 µm, along with derived infrared luminosities from the NRK method based on galaxies' locations in the restframe color-color diagram (N U V − r) vs. (r − K), we are able to more accurately determine total SFRs for our complete sample. At all redshifts, the relationship between median SF R and M * follows a powerlaw at low stellar masses, and flattens to nearly constant SFR at high stellar masses. We describe a new parameterization that provides the best fit to the main sequence and characterizes the low mass power-law slope, turnover mass, and overall scaling. The turnover in the main sequence occurs at a characteristic mass of about M 0 ∼ 10 10 M at all redshifts. The low mass power-law slope ranges from 0.9-1.3 and the overall scaling rises in SFR as a function of (1 + z) 4.12±0.10 . A broken power-law fit below and above the turnover mass gives relationships of SF R ∝ M 0.88±0.06 * below the turnover mass and SF R ∝ M 0.27±0.04 * above the turnover mass. Galaxies more massive than M * 10 10 M have on average, a much lower specific star formation rate (sSFR) than would be expected by simply extrapolating the traditional linear fit to the main sequence found for less massive galaxies.

THE SFR–M* RELATION AND EMPIRICAL STAR FORMATION HISTORIES FROM ZFOURGE AT 0.5 < z < 4*

“…In agreement with recent results, we find that SFRs are roughly proportional to stellar mass at low masses (10 10.2 M e ), but that this trend flattens at higher masses (see also Whitaker et al 2014;Lee et al 2015;Schreiber et al 2015;Tasca et al 2015). Furthermore, although the evolution of the SFR-M * relation is still predominantly in normalization, the slope at high masses (M *  10 10.2 M e ) is also changing.…”

“…Furthermore, although the evolution of the SFR-M * relation is still predominantly in normalization, the slope at high masses (M *  10 10.2 M e ) is also changing. Similar to Lee et al (2015) and Tasca et al (2015) we find that the transition mass at which this flattening occurs evolves with redshift; this is true whether or not quenched galaxies are included. Full parameterizations of the SFR-M * relation with respect to redshift, Ψ(z, M * ), for both all and star-forming galaxies are presented in Section 3.3 and shown in Figures 7 and 8.…”

“…Also shown are recent measurements from literature. There is excellent agreement at the overlapping redshifts between our measurements and those of Lee et al (2015) and Gavazzi et al (2015). We do observe a roughly uniform offset of ≈0.5 dex with Tasca et al (2015) which may be the result of a different parameterization used to measure the turnover mass.…”

The relationship between star formation activity and galaxy structural properties in CANDELS and a semi-analytic model

“…While the SFR-M * correlation is known to have some dispersion, in order to judge distance from the main sequence, we define it with a single line, as has been done in W11 and Bluck et al (2014). We also note that while the observed main sequence slope is known to flatten toward higher stellar mass (Whitaker et al 2012;Schreiber et al 2015;Lee et al 2015), here we extrapolate the slope derived for lower stellar mass galaxies to higher mass. We do this following the interpretation that the decrease in slope at higher stellar mass is due to the higher probability the galaxies of larger mass are already starting to quench and move off of the main sequence.…”

Feedback and Feeding in the Context of Galaxy Evolution withSPICA: Direct Characterisation of Molecular Outflows and Inflows

“…This "bending" is more pronounced at low redshifts (e.g. Lee et al 2015;Schreiber et al 2016). The cause of this bending has not been established, but it has been suggested that it might be associated with the formation of ellipticals through environmental quenching (e.g.…”