Abstract
Abstract We introduce a collection of primarily centrally star-forming galaxies that are selected by disk color to have truncated disk star formation. We show that common explanations for centrally concentrated star formation—low stellar mass, bars, and high-density environments—do not universally apply to this sample. To gain insight into our sample, we compare these galaxies to a parent sample of strongly star-forming galaxies and to a parent sample of galaxies with low specific star formation rates. We find that in star formation and color space from ultraviolet to the infrared these galaxies either fall between the two samples or agree more closely with galaxies with high specific star formation rates. Their morphological characteristics also lie between high and low specific star formation rate galaxies, although their Petrosian radii agree well with that of the low specific star formation rate parent sample. We discuss whether this sample is likely to be quenching or showing an unusual star formation distribution while continuing to grow through star formation. Future detailed studies of these galaxies will give us insights into how the local conditions within a galaxy balance environmental influence to govern the distribution of star formation. In this first paper in a series, we describe the global properties that identify this sample as separate from more average spiral galaxies, and we identify paths forward to explore the underlying causes of their differences.
Highlights
Over the last two decades, galaxy population studies at low to intermediate redshift have exposed a fundamental evolution in the overall galaxy population since a redshift of z∼2 (Bell et al 2004; Faber et al 2007; Muzzin et al 2013; Ilbert et al 2013; Tomczak et al 2014; Moutard et al 2016)
We examine our sample in WISE color (drawn from the VAGC (Blanton et al 2005; Abazajian et al 2009)), to see where the galaxies lie with respect to the InfraRed Transition Zone (IRTZ, Alatalo et al (2014))
The blue WISE colors are less of a mystery, as Alatalo et al (2014) show that galaxies will transition in optical colors before WISE colors, and the blue WISE colors indicate the presence of ISM gas
Summary
Over the last two decades, galaxy population studies at low to intermediate redshift have exposed a fundamental evolution in the overall galaxy population since a redshift of z∼2 (Bell et al 2004; Faber et al 2007; Muzzin et al 2013; Ilbert et al 2013; Tomczak et al 2014; Moutard et al 2016). Observations with MUSE and CALIFA have explored specific star formation through the use of resolved gas and stellar populations, respectively (Perez et al 2013; Lopez Fernandez et al 2018; Erroz-Ferrer et al 2019) They find results consistent with the inside-out path for spiral galaxy growth. Some galaxies have been observed to fall outside of standard morphological categories in a way that may indicate a transitional nature, such as the recent “red misfits” of Evans et al (2018) These misfits tend to be massive star-forming galaxies with active galactic nuclei (AGN). We identify a class of galaxies that falls outside of the red-bulge, blue-disk (or inside-out) formation model: primarily centrally star-forming galaxies that are selected by disk optical color to have truncated disk star formation.
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