Analysis of theSFR–M^∗plane atz< 3: single fitting versus multi-Gaussian decomposition

Abstract

The analysis of galaxies on the star formation rate -stellar mass (SFR-M * ) plane is a powerful diagnostic for galaxy evolution at different cosmic times. We consider a sample of 24463 galaxies from the CANDELS/GOODS-S survey to conduct a detailed analysis of the SFR-M * relation at redshifts 0.5 z <3 over more than three dex in stellar mass. To obtain SFR estimates, we utilise mid-and far-IR photometry when available, and rest-UV fluxes for all the other galaxies. We perform our analysis in different redshift bins, with two different methods: 1) a linear regression fitting of all star-forming galaxies, defined as those with specific star formation rates log 10 (sSFR/yr −1 ) > −9.8, similarly to what is typically done in the literature; 2) a multi-Gaussian decomposition to identify the galaxy main sequence (MS), the starburst sequence and the quenched galaxy cloud. We find that the MS slope becomes flatter when higher stellar mass cuts are adopted, and that the apparent slope change observed at high masses depends on the SFR estimation method. In addition, the multi-Gaussian decomposition reveals the presence of a starburst population which increases towards low stellar masses and high redshifts. We find that starbursts make up ∼ 5% of all galaxies at z = 0.5 − 1.0, while they account for ∼ 16% of galaxies at 2 < z < 3 with log 10 (M * /M o ) =8.25-11.25. We conclude that the dissection of the SFR-M * in multiple components over a wide range of stellar masses is necessary to understand the importance of the different modes of star formation through cosmic time.

Star Formation in Galaxies at z ∼ 4–5 from the SMUVS Survey: A Clear Starburst/Main-sequence Bimodality for Hα Emitters on the SFR–M* Plane

“…, showing that the starburst phenomenon is much more common among intermediate-mass than massive galaxies at z 4 5 -, consistently to what is predicted by theoretical galaxy models (e.g., Cowley et al 2017) and observed at lower redshifts (e.g., Bisigello et al 2017).…”

“…Here we show, for the first time, that starburst galaxies make a clearly distinct sequence on the SFR-M * plane and constitute a significant percentage ( 15% ) of all galaxies with M 9.2 log 10.8 10 *   at z 3.9 4.9   . Only a slightly smaller percentage is obtained at z 2 3 -when a broad dynamic range in stellar mass is considered, albeit with significantly lower sSFR (Bisigello et al 2017). We find that the fraction of starburst galaxies has a strong dependence on stellar mass, varying from ∼0.25 at M log 9.3 10 *( ) to 0.05…”

“…We caution the reader against a wrong interpretation: this coincidence is just fortuitous, as our own main sequence is an upper limit and the Speagle et al (2014) and Whitaker et al (2014) main sequences include all star-forming galaxies, so any direct comparison could be misleading. Our main-sequence determination can be more fairly compared with that of Bisigello et al (2017) at z 2.5 , which has been obtained after a starburst segregation. Taking into account that our own main sequence at z 3.9 4.9 = -is an upper limit to the true main sequence at these redshifts, we can conclude that there is probably little or no evolution of this sequence between z 2.5 and z 3.9 4.9 = -.…”

“…For reference, we also show some recent main-sequence determinations at z 2 3 < < Whitaker et al 2014;Bisigello et al 2017). Among these literature results, only the Bisigello et al (2017) curve has been obtained after performing a starburst/main-sequence separation as we do here. The others fit all star-forming galaxies onto a single sequence.…”

Very Compact Millimeter Sizes for Composite Star-forming/AGN Submillimeter Galaxies

“…All SMGs here have redshift information and a single component at ∼0 2 resolution. More than 15 out of the 25 are located above 4´the main sequence at z 2 in the stellar mass versus SFR plane (Figure 2), indicating that the majority of the sample are starbursts (Bisigello et al 2017). Note that among the 29 SMGs with z=1-3, four are not used in the analysis: two SMGs are not detected at 24 μm and the other are blended in the IRAC maps.…”