Massive compact galaxies with high-velocity outflows: morphological analysis and constraints on AGN activity

Abstract

We investigate the process of rapid star formation quenching in a sample of 12 massive galaxies at intermediate redshift (z ∼ 0.6) that host high-velocity ionized gas outflows (v > 1000 km s −1 ). We conclude that these fast outflows are most likely driven by feedback from star formation rather than active galactic nuclei (AGN). We use multiwavelength survey and targeted observations of the galaxies to assess their star formation, AGN activity, and morphology. Common attributes include diffuse tidal features indicative of recent mergers accompanied by bright, unresolved cores with effective radii less than a few hundred parsecs. The galaxies are extraordinarily compact for their stellar mass, even when compared with galaxies at z ∼ 2 -3. For 9/12 galaxies, we rule out an AGN contribution to the nuclear light and hypothesize that the unresolved core comes from a compact central starburst triggered by the dissipative collapse of very gas-rich progenitor merging disks. We find evidence of AGN activity in half the sample but we argue that it accounts for only a small fraction ( 10%) of the total bolometric luminosity. We find no correlation between AGN activity and outflow velocity and we conclude that the fast outflows in our galaxies are not powered by on-going AGN activity, but rather by recent, extremely compact starbursts.

Massive Quenched Galaxies at z ∼ 0.7 Retain Large Molecular Gas Reservoirs

“…ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada), NSC and ASIAA . Top: median stacked spectra of "K+A" (French et al 2015;blue), "active" (Sell et al 2014;orange), and "A" type (black) post-starburst galaxies. Bottom: Hδ A vs. D n 4000 for the same three post-starburst samples.…”

“…In Figure 4, we show for comparison the low-redshift "K+A" post-starburst galaxies in French et al (2015), an "active" poststarburst galaxy in the Sell et al (2014) sample observed in CO by Geach et al (2013), and star-forming and quiescent galaxies at z∼0 (COLDGASS, Saintonge et al 2011; ATLAS-3D, Cappellari et al 2011Cappellari et al , 2013Young et al 2011;Davis et al 2013Davis et al , 2014and MASSIVE, Davis et al 2016) …”

Morphology Dependence of Stellar Age in Quenched Galaxies at Redshift ∼1.2:Massive Compact Galaxies Are Older than More Extended Ones

“…(Similar Lyα signatures were identified among quenching galaxies by Taniguchi et al 2015. )They interpreted these observational signatures as related to the compact galaxies having enhanced feedback in the ISMdue to ahigher surface density of star formation than their more extended counterparts (see also Diamond-Stanic et al 2012;Sell et al 2014;Alexandroff et al 2015;Heckman & Borthakur 2016), plausibly leading to the truncation of future star formation.…”

STORM IN A “TEACUP”: A RADIO-QUIET QUASAR WITH ≈10 kpc RADIO-EMITTING BUBBLES AND EXTREME GAS KINEMATICS

“…Indeed, extremely compact star-forming regions, with SFRs of ≈200 M yr −1 and sizes ≈100 pc, have been attributed to driving ≈1000 km s −1 outflows (Heckman et al 2011;DiamondStanic et al 2012;Sell et al 2014). However, maximum velocities as high as that observed around the HR-B radio structure (i.e., v max ≈ 1100 km s −1 ) are not seen in non-AGN host galaxies with SFRs comparable to that of the "Teacup" AGN (i.e., SFRs ≈ 10 M yr −1 ; e.g., Genzel et al 2011;Arribas et al 2014) and compact starbursts are often associated with flatter radio spectral indices than that observed here (Murphy et al 2013).…”