Complex molecular gas kinematics in the inner 5 kpc of 4C12.50 as seen by ALMA

M Papachristou,F Combes,K M Dasyra,C M Fotopoulou,P Salomé

doi:10.1051/0004-6361/201834416

Abstract

The nearby system 4C12.50, also known as IRAS 13451+1217 and PKS 1345+12, is a merger of gas-rich galaxies with infrared and radio activity. It has a perturbed interstellar medium (ISM) and a dense configuration of gas and dust around the nucleus. The radio emission at small (∼100 pc) and large (∼100 kpc) scales, as well as the large X-ray cavity in which the system is embedded, are indicative of a jet that could have affected the ISM. We carried out observations of the CO(1−0), (3−2), and (4−3) lines with the Atacama Large Millimeter Array (ALMA) to determine basic properties (i.e., extent, mass, and excitation) of the cold molecular gas in this system, including its already-known wind. The CO emission reveals the presence of gaseous streams related to the merger, which result in a small (∼4 kpc-wide) disk around the western nucleus. The disk reaches a rotational velocity of 200 km s−1, and has a mass of 3.8(±0.4) × 109 M⊙. It is truncated at a gaseous ridge north of the nucleus that is bright in [O III]. Regions with high-velocity CO emission are seen at signal-to-noise ratios of between 3 and 5 along filaments that radially extend from the nucleus to the ridge and that are bright in [O III] and stellar emission. A tentative wind detection is also reported in the nucleus and in the disk. The molecular gas speed could be as high as 2200 km s−1 and the total wind mass could be as high as 1.5(±0.1) × 109 M⊙. Energetically, it is possible that the jet, assisted by the radiation pressure of the active nucleus or the stars, accelerated clouds inside an expanding bubble.

Highlights

Previous CO(1−0) interferometric observations taken with the IRAM Plateau de Bure (PdB) array yielded a CO(1−0) flux of 18.2(±1.5) Jy km s−1 at a resolution of 4.0 × 3.8 (Dasyra et al 2014)
We obtained Atacama Large Millimeter Array (ALMA) data of the radio galaxy 4C12.50 in order to determine the millimeter properties of its outflow, which was previously known to exist from large- and small-angularresolution observations at other wavelengths
Some co-rotating CO emission is seen in the secondary nucleus and in a bridge connecting the nuclei

Summary

Introduction

Galactic winds that are driven by the feedback of active galactic nuclei (AGNs) or young stars and that are detected in molecular gas tracers are considered common (Sakamoto et al 2006, 2009, 2014; Leon et al 2007; Feruglio et al 2010; Fischer et al 2010; Fluetsch et al 2019; Alatalo et al 2011, 2014; Rangwala et al 2011; Sturm et al 2011; Krips et al 2011; Dasyra & Combes 2011, 2012; Aalto et al 2012, 2016; Tsai et al 2012; Morganti et al 2013a; Combes et al 2013; Spoon et al 2013; Veilleux et al 2013; Cicone et al 2014; García-Burillo et al 2014; George et al 2014; Tombesi et al 2015; Stone et al 2016; GonzálezAlfonso et al 2017; Pereira-Santaella et al 2018). In galaxies with active nuclei, the momentum rate of the molecular winds is often considerably higher, that is, about 20 times higher, than the pressure exerted by the AGN radiation (e.g., Cicone et al 2014; Carniani et al 2015). Multiple photon scatterings (Ishibashi & Fabian 2015) and, more frequently, an energy-conserving expansion of an ionized gas bubble that leads to momentum boosting (King et al 2011; Faucher-Giguère & Quataert 2012; Zubovas & King 2014) have been evoked to justify the high momentum rates of molecular winds. Radiation pressure can drive such winds during specific phases of the ionized medium expansion: when. Radio jets, when powerful or nearly relativistic, can efficiently drive adiabatically expanding bubbles as they rapidly deposit energy in the interstellar medium (ISM) for most expansion phases (Wagner et al 2016). Several of the molecular winds in the above-mentioned studies were detected in galaxies with AGN jets

Results

Discussion

Conclusion