A Comprehensive X-Ray and Multiwavelength Study of the Colliding Galaxy Pair NGC 2207/Ic 2163

Abstract

We present a comprehensive study of the total X-ray emission from the colliding galaxy pair NGC 2207/IC 2163, based on Chandra, Spitzer, and GALEX data. We detect 28 ultra-luminous X-ray sources ('ULXs'), 7 of which were not detected previously due to X-ray variability. Twelve sources show significant long-term variability, with no correlated spectral changes. Seven sources are transient candidates. One ULX coincides with an extremely blue star cluster (B-V = -0.7). We confirm that the global relation between the number and luminosity of ULXs and the integrated star formation rate ('SFR') of the host galaxy also holds on local scales. We investigate the effects of dust extinction and/or age on the X-ray binary ('XRB') population on sub-galactic scales. The distributions of N X and L X are peaked at L IR /L NUV ∼ 1, which may be associated with an age of ∼10 Myr for the underlying stellar population. We find that ∼1/3 of the XRBs are located in close proximity to young star complexes. The luminosity function of the X-ray binaries ('XRBs') is consistent with that typical for high-mass X-ray binaries, and appears unaffected by variability. We disentangle and compare the X-ray diffuse spectrum with that of the bright XRBs. The hot interstellar medium dominates the diffuse X-ray emission at E 1 keV, has a temperature kT = 0.28 +0.05 −0.04 keV and intrinsic 0.5-2 keV luminosity of 7.9 × 10 40 erg s −1 , a factor of ∼2.3 higher than the average thermal luminosity produced per unit SFR in local star-forming galaxies. The total X-ray output of NGC 2207/IC 2163 is 1.5 × 10 41 ergs s −1 , and the corresponding total integrated SFR is 23.7 M yr −1 .

ALMA CO Clouds and Young Star Complexes in the Interacting Galaxies IC 2163 and NGC 2207

“…The locations of maximum brightness in the N2207 nucleus in 6 cm radio continuum and 8 μm coincide, within the uncertainties, with the Chandra position listed by Mineo et al (2014) of a low-luminosity AGN X-ray source in N2207, which has a nonsymmetric shape of the central AGN in X-rays. The radio continuum is probably from the AGN.…”

Diffuse X-Ray-emitting Gas in Major Mergers

“…These additional systems were obtained from the surveys of Keel & Wu (1995), Gao & Solomon (1999), Rothberg & Joseph (2004), Taylor-Mager et al (2007), Brassington et al (2007), and Ellison et al (2013). We also added the nearby pre-merger pair NGC 2207/IC 2163 (Mineo et al 2014). This brings our final sample to 49 systems.…”

“…They found a total 0.3 − 8 keV luminosity of 2.5 × 10 40 erg s −1 for this region, after correcting for a total (Galactic plus internal) absorption of N H = 5.9 × 10 21 cm −2 obtained from the Hα/24 µm ratio. Mineo et al (2014) extracted and fit the spectrum of the diffuse X-ray light for the entire system, and found a thermal component with kT = 0.28 ± 0.05 0.04 keV, a total (internal plus Galactic) absorption of N H = 2.0 ± 1.4 × 10 21 cm −2 , and an 0.5 − 2 keV L X of 7.9 × 10 40 erg s −1 . Their absorbing column is about twice the value we obtained from the UV/IR ratio but within the uncertainties; their luminosity is a factor of two higher than our determination.…”

Outflow from Outer-arm Starburst in a Grazing Collision between Galaxies

“…References-(1) Elmegreen et al 1995a; (2) In four Chandra observations between 2010 and 2013, Mineo et al (2014) detect Feature i as an elongated soft X-ray source and suggest that it may contain a non-variable Ultta-luminous X-ray Source (ULX) surrounded by hot diffuse gas. The possible ULX and the radio continuum peak coincide within the uncertainties.…”

“…This star complex is too young to host a ULX. Neither Mineo et al (2014) nor Smith et al (2014) measure the X-ray extinction A X within the Feature i core. Assuming an A v of 4 mag to the midplane, Smith et al (2014) deduce the value of A X and get a de-reddened L X ∼ 2 × 10 40 erg s −1 for the 0.5 -10 keV luminosity of the central source in Feature i.…”