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 mass-luminosity relation for late-type stars has long been a critical tool for estimating stellar masses. However, there is growing need for both a higher-precision relation and a better understanding of systematic effects (e.g., metallicity). Here we present an empirical relationship between M K S and M * spanning 0.075M < M * < 0.70M . The relation is derived from 62 nearby binaries, whose orbits we determine using a combination of Keck/NIRC2 imaging, archival adaptive optics data, and literature astrometry. From their orbital parameters, we determine the total mass of each system, with a precision better than 1% in the best cases. We use these total masses, in combination with resolved K S magnitudes and system parallaxes, to calibrate the M K S -M * relation. The resulting posteriors can be used to determine masses of single stars with a precision of 2-3%, which we confirm by testing the relation on stars with individual dynamical masses from the literature. The precision is limited by scatter around the best-fit relation beyond measured M * uncertainties, perhaps driven by intrinsic variation in the M K S -M * relation or underestimated uncertainties in the input parallaxes. We find that the effect of [Fe/H] on the M K S -M * relation is likely negligible for metallicities in the solar neighborhood (0.0±2.2% change in mass per dex change in [Fe/H]). This weak effect is consistent with predictions from the Dartmouth Stellar Evolution Database, but inconsistent with those from MESA Isochrones and Stellar Tracks (at 5σ). A sample of binaries with a wider range of abundances will be required to discern the importance of metallicity in extreme populations (e.g., in the Galactic halo or thick disk).

Though half of cosmic starlight is absorbed by dust and reradiated at long wavelengths (3µm-3 mm), constraints on the infrared through millimeter galaxy luminosity function (the 'IRLF') are poor in comparison to the rest-frame ultraviolet and optical galaxy luminosity function, particularly at z > ∼ 2.5. Here we present a backward evolution model for interpreting number counts, redshift distributions, and cross-band flux density correlations in the infrared and submillimeter sky, from 70µm-2 mm, using a model for the IRLF out to the epoch of reionization. Mock submillimeter maps are generated by injecting sources according to the prescribed IRLF and flux densities drawn from model spectral energy distributions that mirror the distribution of SEDs observed in 0 < z < 5 dusty star-forming galaxies (DSFGs). We explore two extreme hypothetical case-studies: a dust-poor early Universe model, where DSFGs contribute negligibly (<10%) to the integrated star-formation rate density at z > 4, and an alternate dust-rich early Universe model, where DSFGs dominate ∼90% of z > 4 star-formation. We find that current submm/mm datasets do not clearly rule out either of these extreme models. We suggest that future surveys at 2 mm will be crucial to measuring the IRLF beyond z ∼ 4. The model framework developed in this paper serves as a unique tool for the interpretation of multiwavelength IR/submm extragalactic datasets and will enable more refined constraints on the IRLF than can be made from direct measurements of individual galaxies' integrated dust emission.

We combine Herschel PACS and SPIRE maps of the full 2 deg 2 COSMOS field with existing multiwavelength data to obtain template and model-independent optical-to-far-infrared spectral energy distributions (SEDs) for 4,218 Herschel-selected sources with log(L IR /L ) = 9.4-13.6 and z = 0.02-3.54. Median SEDs are created by binning the optical to far-infrared (FIR) bands available in COSMOS as a function of infrared luminosity. Herschel probes rest-frame wavelengths where the bulk of the infrared radiation is emitted, allowing us to more accurately determine fundamental dust properties of our sample of infrared luminous galaxies. We find that the SED peak wavelength (λ peak ) decreases and the dust mass (M dust ) increases with increasing total infrared luminosity (L IR ). In the lowest infrared luminosity galaxies (log(L IR /L ) = 10.0-11.5), we see evidence of Polycyclic Aromatic Hydrocarbons (PAH) features (λ ∼ 7-9 µm), while in the highest infrared luminosity galaxies (L IR > 10 12 L ) we see an increasing contribution of hot dust and/or power-law emission, consistent with the presence of heating from an active galactic nucleus (AGN). We study the relationship between stellar mass and star formation rate of our sample of infrared luminous galaxies and find no evidence that Herschel-selected galaxies follow the SF R/M * "main sequence" as previously determined from studies of optically selected, star-forming galaxies. Finally, we compare the mid-infrared (MIR) to FIR properties of our infrared luminous galaxies using the previously defined diagnostic, IR8 ≡ L IR /L 8 , and find that galaxies with L IR 10 11.3 L tend to systematically lie above (×3-5) the IR8 "infrared main sequence", suggesting either suppressed PAH emission or an increasing contribution from AGN heating.