Stellar properties of the host galaxy of an ultraluminous X-ray source in NGC 5252

Abstract

An ultraluminous X-ray source (ULX) in NGC 5252 has been known as a strong candidate for an off-nuclear intermediate-mass black hole. We present near-infrared imaging data of the ULX obtained with the William Herschel Telescope. Using this data we estimate a stellar mass associated with the ULX of ≈ 10 7.9±0.1 M ⊙ , suggesting that it could be (the remnant of) a dwarf galaxy that is in the process of merging with NGC 5252. Based on a correlation between the mass of the central black hole (BH) and host galaxy, the ULX is powered by a 10 5 M ⊙ black hole. Alternatively, if the BH mass is ≈ 10 6 M ⊙ or larger, the host galaxy of the ULX must have been heavily stripped during the merger. The ULX K s -band luminosity is two orders of magnitude smaller than that expected from an ordinary active galactic nucleus with the observed [O iii] luminosity, which also suggests the ULX lacks a dusty torus. We discuss how these findings provide suggestive evidence that the ULX is hosting an intermediate-mass black hole.

The Nature of the IMBH Candidate CXO J133815.6+043255: High-frequency Radio Emission

“…These objects include NGC 5408 X-1, which is likely to be a stellar-mass object accreting at super-Eddington rates and driving a wind nebula (Pinto et al 2016;Luangtip et al 2021); Homberg II X-1, which is unlikely to be >100 M e and accreting at slightly sub-Eddington (Goad et al 2006;Ambrosi et al 2022); M 82 X1, whose nature is uncertain but may be a few ×100 M e black hole (Pasham et al 2014;Mondal et al 2022); and NGC 7424 ULX-2, which is located in a young OB association but does exhibit a steep radio spectrum like our source (Soria et al 2006). In short, most of these objects are either stellar-mass objects, or at least are well below the mass range established for CXO J1338+04 by previous investigations: 10 3.5 M e < M BH < 10 6.3 M e from Mezcua et al (2018) and 10 5 M e by Kim et al (2020). In fact, the majority of ULXs may be stellar-mass objects accreting at or above the Eddington rate (e.g., Berghea et al 2008), so if CXO J1338+04 is a bona fide intermediate-mass black hole producing a real analog of a radio-loud quasar jet, we might expect its L R /L X ratio to exceed that of other ULXs, as we observe here.…”

“…Using the black hole fundamental plane (Merloni et al 2003), they constrain the black hole mass to 10 3.5 M e < M BH < 10 6.3 M e . Finally, Kim et al (2020) conducted near-infrared (NIR) imaging of the source with the Herschel space telescope to study the stellar properties of the putative remnant dwarf host, finding a stellar mass of M * = 10 7.9 M e for the remnant galaxy, and used scaling relations to estimate the IMBH mass at 10 5 M e .…”

Intermediate mass black hole formation in compact young massive star clusters

“…1 The lower and upper mass boundaries depend on the stellar evolution model, i.e. details of stellar wind mass loss and supernova explosions Other notable sources in the same category are NGC 5252 and NGC 2276-3C, which have been estimated to host IMBHs of ∼ 10 5 M Kim et al (2020) and ∼ 5 × 10 4 M (Mezcua et al 2013(Mezcua et al , 2015, respectively. Another HLX is M82 X-1.…”

Potential Black Hole Seeding of the Spiral Galaxy NGC 4424 via an Infalling Star Cluster

“…The phenomenon of an infalling galaxy undergoing assimilation has been offered to explain the offset IMBH in ESO 243-49 (Farrell et al 2009;Bellovary et al 2010;Mapelli et al 2012;Webb et al 2017;Bellovary et al 2021;Ricarte et al 2021) and the ULX sources likely associated with a massive black hole in galaxies such as IC 4320 (Sutton et al 2012), NGC 5252 (Kim et al 2015(Kim et al , 2020, NGC 2276-3c (Mezcua et al 2015) and others. One such interesting example can be seen in the Virgo cluster galaxy NGC 4651 (Martínez-Delgado et al 2010;Foster et al 2014;Morales et al 2018), where the elongation process associated with infall has produced a tidal stream (Newberg 2016) which is immediately evident in optical images.…”