科研之友
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摘要
The point-like X-ray source HLX-1, close to the S0 galaxy ESO 243-49, is the brightest known ultraluminous X-ray source and one the strongest intermediate-mass black hole candidates. We argue that the counterpart of HLX-1 may be the nucleus of a satellite galaxy, undergoing minor merger with the S0 galaxy. We investigate this scenario by running a set of N-body/smoothed particle hydrodynamics simulations of the minor merger between an S0 galaxy and a gas-rich bulgy satellite galaxy, and by comparing the results with the available photometric Hubble Space Telescope (HST) data of ESO 243-49 and of the HLX-1 counterpart. In particular, we derive synthetic surface brightness profiles for the simulated counterpart of HLX-1 in six HST filters, ranging from far-ultraviolet (FUV) to infrared wavelengths. Such synthetic profiles include a contribution from the stellar population associated with the simulated disrupted satellite and a contribution from an irradiated disc model. These are in reasonable agreement with the observed surface brightness profiles of the HLX-1 counterpart, provided that the merger is at sufficiently late stage (greater than or similar to 2.5 Gyr since the first pericentre passage). The main difference between models and observations is in the FUV band, where the HST image shows a fuzzy and extended emission. %26lt;br%26gt;We show that the spectral energy distribution of the bulge of ESO 243-49 cannot be explained with a single old stellar population, but requires the existence of a younger stellar component. This is in good agreement with the star formation history derived from our N-body simulations, and is a further hint for the minor merger scenario.
- 出版日期2013-7
