The stellar host in star-forming low-mass galaxies: Evidence for two classes

A. Lumbreras-Calle; J. Méndez-Abreu; C. Muñoz-Tuñón

doi:10.1051/0004-6361/201935288

paper

The stellar host in star-forming low-mass galaxies: Evidence for two classes

arXiv:1904.10462 · doi:10.1051/0004-6361/201935288

Abstract

The morphological evolution of star-forming galaxies provides important clues to understand their physical properties, as well as the triggering and quenching mechanisms of star formation. We aim at connecting morphology and star-formation properties of low-mass galaxies (median stellar mass $\sim$ 10 $^{8.5}$ M $_{⊙}$ ) at low redshift ( $z < 0.36$ ). We use a sample of medium-band selected star-forming galaxies from the GOODS-North field. H $α$ images for the sample are created combining both spectral energy distribution fits and HST data. Using them, we mask the star forming regions to obtain an unbiased two-dimensional model of the light distribution of the host galaxies. For this purpose we use $PHI$ , a new Bayesian photometric decomposition code. We apply it independently to 7 HST bands assuming a Sérsic surface brightness model. Star-forming galaxy hosts show low Sérsic index (with median $n$ $\sim$ 0.9), as well as small sizes (median $R_{e}$ $\sim$ 1.6 kpc), and negligible change of the parameters with wavelength (except for the axis ratio, which grows with wavelength). Using a clustering algorithm, we find two different classes of star-forming galaxies: A more compact, redder, and high- $n$ (class A) and a more extended, bluer and lower- $n$ one (class B). We also find evidence that the first class is more spheroidal-like. In addition, we find that 48% of the analyzed galaxies present negative color gradients (only 5% are positive). The host component of low-mass star-forming galaxies at $z < 0.36$ separates into two different classes, similar to what has been found for their higher mass counterparts. The results are consistent with an evolution from class B to class A. Several mechanisms from the literature, like minor and major mergers, and violent disk instability, can explain the physical process behind the likely transition between the classes. [abridged]

arXiv commentAccepted for publication in Astronomy & Astrophysics. 13 pages, 11 figures

The stellar host in star-forming low-mass galaxies: Evidence for two classes

Abstract

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