MUSE view of Arp220: Kpc-scale multi-phase outflow and evidence for positive feedback

Abstract

Context. Arp220 is the nearest and prototypical ultra-luminous infrared galaxy; it shows evidence of pc-scale molecular outflows in its nuclear regions and strongly perturbed ionised gas kinematics on kpc scales. It is therefore an ideal system for investigating outflow mechanisms and feedback phenomena in detail. Aims. We investigate the feedback effects on the Arp220 interstellar medium (ISM), deriving a detailed picture of the atomic gas in terms of physical and kinematic properties, with a spatial resolution that had never before been obtained (0.56″, i.e. ∼210 pc). Methods. We use optical integral-field spectroscopic observations from VLT/MUSE-AO to obtain spatially resolved stellar and gas kinematics, for both ionised ([N II]λ6583) and neutral (Na IDλλ5891, 96) components; we also derive dust attenuation, electron density, ionisation conditions, and hydrogen column density maps to characterise the ISM properties. Results. Arp220 kinematics reveal the presence of a disturbed kpc-scale disc in the innermost nuclear regions as well as highly perturbed multi-phase (neutral and ionised) gas along the minor axis of the disc, which we interpret as a galactic-scale outflow emerging from the Arp220 eastern nucleus. This outflow involves velocities up to ∼1000 km s−1 at galactocentric distances of ≈5 kpc; it has a mass rate of ∼50 M⊙ yr−1 and kinetic and momentum power of ∼1043 erg s−1 and ∼1035 dyne, respectively. The inferred energetics do not allow us to distinguish the origin of the outflows, namely whether they are active galactic nucleus- or starburst-driven. We also present evidence for enhanced star formation at the edges of – and within – the outflow, with a star-formation rate SFR ∼ 5 M⊙ yr−1 (i.e. ∼2% of the total SFR). Conclusions. Our findings suggest the presence of powerful winds in Arp220: They might be capable of heating or removing large amounts of gas from the host (“negative feedback”) but could also be responsible for triggering star formation (“positive feedback”).

Physics of ULIRGs with MUSE and ALMA: The PUMA project

“…In order to appreciate the MUSE data quality and its scientific potential, in this section we present three-colour, continuum, and emission line maps built directly from the MUSE data cubes, and briefly describe the general properties that can be inferred from them. A full characterisation of the systems, similar to the one obtained for Arp220 (Perna et al 2020;Catalán-Torrecilla et al, in prep. ), will be presented in future papers.…”

“…Finally, these images provide a first-order identification of foreground stars, generally associated with bright point-like sources, and galaxies at different redshifts, showing a heterogeneous mix of morphologies, colours, and sizes (see also e.g. Perna et al 2020). Nine ULIRGs in our sample present between one and two nearby satellites in the MUSE FOV at projected distances from ∼ 5 to ∼ 50 kpc (see e.g.…”

“…For each bright star in the FOV, we performed a 2D Gaussian fit, and derived an estimate for the angular resolution from the FWHM of the Gaussian fit. The spatial resolution in the data cube of F11095−0238 was obtained from a 2D Gaussian fit of the broad-line region (BLR) emission of a quasi-stellar object (QSO) at z ∼ 2.2 (CXOGSG J111204.2-025415); the spectral resolution of Arp220 was taken from Perna et al (2020). Because of the MUSE seeing-enhancer mode (and the good seeing conditions during the acquisition of seeing-limited MUSE data), we reached an overall average resolution of ∼ 0.7 , corresponding to physical scales in the range ∼ 0.2 − 2 kpc depending on the redshift of the system (Table 2).…”

“…Sect. 10.5 in Perna et al 2020). In this section, we therefore investigate the possible connection between AGN and SB activity and the atomic outflow velocities.…”

“…More detailed analyses of the outflow nature will be presented in future papers, however, together with detailed spatially resolved properties of neutral and ionised outflows (e.g. Perna et al 2020).…”