Evolution of Intrinsic Scatter in the SFR-Stellar Mass Correlation at 0.5<z<3

TL;DR

This study measures the intrinsic scatter in the SFR-Stellar Mass relation from redshift 0.5 to 3, revealing a gradual increase over cosmic time and extending to very low-mass galaxies, supporting a self-similar galaxy assembly model.

Contribution

It provides the first detailed measurement of intrinsic scatter in the SFR-M* relation down to 10^7 Msun across a broad redshift range, using ultra-deep photometry.

Findings

Intrinsic scatter increases from 0.2 to 0.4 dex over time.

Slope of the SFR-M* relation is near unity at all redshifts.

No significant increase in scatter at low mass within the studied timescales.

Abstract

We present estimates of intrinsic scatter in the Star Formation Rate (SFR) - Stellar Mass (M*) correlation in the redshift range 0.5 < z < 3.0 and in the mass range 10^7 < M* < 10^11 Msun. We utilize photometry in the Hubble Ultradeep Field (HUDF12), Ultraviolet Ultra Deep Field (UVUDF) campaigns and CANDELS/GOODS-S. We estimate SFR, M* from broadband Spectral Energy Distributions (SEDs) and the best available redshifts. The maximum depth of the HUDF photometry (F160W 29.9 AB, 5 sigma depth) probes the SFR-M* correlation down to M* ~ 10 ^7 Msun, a factor of 10-100X lower in M* than previous studies, and comparable to dwarf galaxies in the local universe. We find the slope of the SFR-M* relationship to be near unity at all redshifts and the normalization to decrease with cosmic time. We find a moderate increase in intrinsic scatter with cosmic time from 0.2 to 0.4 dex across the epoch of peak cosmic star formation. None of our redshift bins show a statistically significant increase in intrinsic scatter at low mass. However, it remains possible that intrinsic scatter increases at low mass on timescales shorter than ~ 100 Myr. Our results are consistent with a picture of gradual and self-similar assembly of galaxies across more than three orders of magnitude in stellar mass from as low as 10^7 Msun.