X-Ray Emission from the Nuclear Region of Arp 220

Abstract

We present an imaging and spectral analysis of the nuclear region of the ULIRG merger Arp 220, using deep Chandra-ACIS observations summing up to ∼ 300 ks. Narrow-band imaging with sub-pixel resolution of the innermost nuclear region reveals two distinct Fe-K emitting sources, coincident with the infrared and radio nuclear clusters. These sources are separated by 1' (∼ 380 pc). The X-ray emission is extended and elongated in the eastern nucleus, like the disk emission observed in millimeter radio images, suggesting starburst dominance in this region. We estimate Fe-K equivalent width 1 keV for both sources, and observed 2-10 keV luminosities ∼ 2 × 10 40 erg s −1 (W) and ∼ 3 × 10 40 erg s −1 (E). In the 6-7 keV band the emission from these regions is dominated by the 6.7 keV Fe xxv line, suggesting contribution from collisionally ionized gas. The thermal energy content of this gas is consistent with kinetic energy injection in the interstellar medium by Type II SNe. However, nuclear winds from hidden AGN ( ∼ 2000 km s −1 ) cannot be excluded. The 3σ upper limits on the neutral Fe-Kα flux of the nuclear regions correspond to intrinsic AGN 2-10 keV luminosities < 1 × 10 42 erg s (W) and < 8 × 10 43 erg s −1 (E), and black hole masses < 1 × 10 5 M (W) and < 5 × 10 5 M (E) for Eddington limited AGNs with a standard 10% efficiency.

Cosmic ray transport and radiative processes in nuclei of starburst galaxies

“…The different emission in the hard X-ray band between Models A and B on one hand and Model C on the other illustrate well the potential importance of the detection of hard X-rays from SBNi, in that such photons carry information about the calorimetric properties of the SBN. Although hard X-rays from the cores of SBGs have been observed (Strickland & Heckman 2007;Paggi et al 2017;Wik et al 2014), an important contribution to such diffuse emission is typically attributed to unresolved X-ray binaries (XBs), SNRs, O or early-B spectral type stars, diffuse thermal plasma and a possible AGN activity (for a detailed discussion of these components see Persic & Rephaeli 2002). CR electrons are also expected to contribute to the diffuse hard X-ray emission mainly through ICS on the IR background (see Persic & Rephaeli 2002).…”

“…The multifrequency spectrum of Arp220 is shown in Figure 7. Gamma ray observations (see Peng et al 2016) suggest that Arp220 requires a softer injection slope with (2016), whereas the X-ray point (which again we take as upper limit for our diffuse flux taking into account possible contamination from pointlike sources and thermal plasma) has been taken from Paggi et al (2017).…”

“…The diffuse hard X-ray flux from the central region of Arp220 has been investigated by Paggi et al (2017). Taking into account that we are modelling the core of Arp220 as a unique region we show their measured X-ray luminosity coming from the central 4.5 , corresponding to a radius of ∼ 840 pc that also accounts for the region between the two nuclei (see X-ray upper limit in the lower panel of Figure 7).…”

Cosmic rays escaping from Galactic starburst-driven superbubbles

“…For example, it could be applied to superbubbles in various starburst galaxies, such as Arp 220 (e.g. Anantharamaiah et al 2000;Paggi et al 2017) and extragalactic 'Fermi Bubbles' in NGC 3079 (e.g. Li et al 2019).…”

Astrophysics: Macroobject Shell Model

“…Observations with NASA's Chandra X-ray Observatory have also revealed X-rays in the range 2 -10 keV coming from both cores [47]. The collision, which began about 700 million years ago, has sparked a cracking burst of star formation, resulting in about 200 huge star clusters in a packed, dusty region about 5000…”