極亮X光源（ultraluminous X-ray sources）是在河外星系中發現的偏離中心的X光
點光源，具有X光亮度高於每秒1E39爾格，此亮度約為10倍太陽質量的恆星質
量黑洞的愛丁頓極限（Eddington limit）。一般的X光雙星（X-ray binary）以約每
秒1E36-38爾格的較低效率發光，難以解釋極亮X光源的亮度，然而，這些偏離星系
中心的點源不太可能以超大質量的黑洞來解釋。鑑於此，涉及不同輻射過程的假說
則被提出用以解釋這種異常明亮的X光源。例如，極亮X光源可以是中等質量的黑
洞或更高質量的X光雙星，借此獲得更高的愛丁頓極限。或者，極亮X光源可以通
過超級愛丁頓吸積流超過愛丁頓極限。但是，要探討極亮X光源的性質，它需要高
品質的光譜，成像和長期監控。由於有限的觀測時間，只有少數極亮X光源受到
關注，並獲得對其結構、光度、光譜和光度變化的深入研究。此外，有關完整極
亮X光源的數量與特性普查以及與其宿主環境的關係（例如恆星形成活動和對應之
恆星特性）的研究受限於距離我們較近的星系。

本論文通過探索從錢德拉X光望遠鏡，史隆數位化巡天和史匹哲太空望遠鏡獲得
之X光到紅外線數據，並著重研究極亮X光源種群和環境，而樣本是來自於距離我
們約4千9百萬秒差距內的鄰近星系合併（galaxy merger）。為了克服部分極亮X光
源的X光光子數過低的問題，我們使用貝葉斯（Bayesian）方法來分析其冪律能量
光譜（power-law energy spectra）和柱密度（column density）的特性。在極亮X光源
周圍的區域，我們使用兩種方法估算恆星形成率（star formation rate）和恆星質量
（stellar mass）：光學到紅外光譜能量分佈擬合以及使用紅外線通量的經驗公式。
在我們的研究中，我們從16個星系合併中獲得了42個極亮X光源候選對象。X光特
性表明光子指數（photon index）的分佈與過去的極亮X光源群體研究一致。柱密
度可以解釋X光顏色的吸收特徵，而吸收效果不能僅由附近的恆星形成率和恆星質
量來解釋，這暗示著有其他的吸收源來自極亮X光源系統內部或星際塵埃。在X光
亮度於每秒1-5倍1E39爾格與光子指數介於0.5-2的子樣本中， 其X光的亮度和恆星形
成率以及恆星質量的關係變得顯著，由此我們推得極亮X光源種群中可能有一種以
上的種類，而某些極亮X光源可能起源於X光雙星的X光亮度函數（X-ray luminosity
function）的高亮度端。

Ultraluminous X-ray sources (ULXs) are extragalactic off-center X-ray point sources with X-ray luminosities Lx ≥ 1039 erg s−1, which is typically the Eddington limit for a ∼ 10 M。stellar-mass black hole. Ordinary X-ray binaries (XRB), shining at a lower rate of 1036−38 erg s−1, cannot be accounted for the ULX luminosity, while these non-nuclear populations are unlikely to be supermassive black holes. Given this, hypotheses invoking different radiation processes are proposed to explain this unusually bright X-ray luminosity. For instance, ULXs may be intermediate-mass black holes or massive XRBs to allow a higher Eddington limit. Or, ULXs can exceed the Eddington limit through super-Eddington accretion flow. However, to examine the nature of ULXs, it requires high-quality spectroscopy, imaging and long-term monitoring. Due to limited observation time, only a handful of ULXs are under the spotlight and well studied for their structures, luminosities, spectra, and variability. Moreover, studies on the complete ULX census and their relation to their hosting environment (e.g. star formation activities, stellar counterparts) are restricted to nearby galaxies.

This thesis focuses on ULX populations and environments by exploring the X-ray to infrared data obtained from the Chandra X-ray observatory, the Sloan Digital Sky Survey and the Spitzer Space Telescope for a galaxy merger sample (D<48.9Mpc). To overcome the low X-ray count for some ULXs, we use a Bayesian approach to constrain their power-law energy spectra and column densities. For the sub-galactic regions around ULXs, we estimate the star formation rate (SFR) and stellar mass (M*) using two methods: optical- to-infrared spectral energy distribution fitting and empirical formulae using infrared fluxes. In our study, we create a clean sample of 42 ULX candidates selected from 16 galaxy mergers. The X-ray properties suggest that the photon index distribution be consistent with previous ULX population study. The column density can explain the absorbed features of the X-ray colors, while the absorption effect cannot be solely explained by the nearby SFR and M*, indicating other absorption from inside the ULX systems or interstellar dust. For a sub-sample of Lx=1-5× 1039 erg s−1 and 「=0.5-2.0, a relation between the X-ray luminosity and SFR and stellar mass emerges, implying there could be more than one species in the ULX population and some ULXs could be originated from the luminous end of X-ray binaries.

Abstract...............................................................i
Acknowledgements.......................................................iv
Table of Contents......................................................vi
List of Figures........................................................viii
List of Tables.........................................................x

1 Introduction......................................................1
1.1 Ultraluminous X-ray sources......................................2
1.1.1 X-ray binaries................................................3
1.1.2 Intermediate-mass black holes.................................5
1.1.3 Pulsating ultraluminous X-ray sources.........................6
1.1.4 Supernovae and supernova remnants.............................7
1.1.5 Background active galactic nuclei.............................8
1.2 Emission mechanisms and spectral properties.....................9
1.2.1 Accretion.....................................................10
1.2.2 Mass accretion rate and beaming effect........................11
1.2.3 Comptonization................................................15
1.2.4 Absorption....................................................15
1.3 A brief overview of observational studies of ULXs...............16
1.4 Motivation and objectives of this work..........................19

2 Sample Selection..................................................20
2.1 Major merger samples............................................20
2.2 Multi-wavelength data...........................................21
2.2.1 Chandra X-ray Observatory.....................................22
2.2.2 Sloan Digital Sky Survey......................................24
2.2.3 Spitzer IRAC..................................................25
2.3 Additional data.................................................26
2.4 X-ray detection limit and final galaxy sample...................28

3 X-ray Data Reduction and Analysis.................................30
3.1 Data preparation................................................30
3.2 Photometric analysis............................................32
3.2.1 ULX candidate identification..................................32
3.2.2 Spurious ULX removal..........................................32
3.2.3 Background contamination......................................33
3.2.4 X-ray color and hardness ratio................................39
3.3 Spectral analysis...............................................41
3.4 Discussion......................................................48
3.4.1 Photometric properties........................................49
3.4.2 Spectral properties...........................................53

4 Optical and Infrared Data Analysis................................58
4.1 Data processing.................................................58
4.2 Photometry of the ULX environment...............................64
4.3 Spectral energy distribution fitting analysis...................70
4.3.1 Introduction to MAGPHYS.......................................70
4.3.2 Fitting process...............................................72
4.4 Discussion......................................................75
4.4.1 Stellar mass..................................................75
4.4.2 Star formation rate...........................................78
4.4.3 Connection between the ULX nature and ULX environment.........80

5 Summary and Future Work...........................................88
5.1 Summary.........................................................88
5.2 Future work.....................................................90
5.2.1 The physical size of the ULX environment......................90
5.2.2 Star formation rate indicators................................90
5.2.3 The credibility of SED fitting................................91

Aniano, G., Draine, B. T., Gordon, K. D., and Sandstrom, K. (2011). Common-resolution convolution kernels for space- and ground-based telescopes. Publications of the Astronomical Society of the Pacific, 123(908):1218–1236.

Bachetti, M., Harrison, F. A., Walton, D. J., Grefenstette, B. W., Chakrabarty, D., Fürst, F., Barret, D., Beloborodov, A., Boggs, S. E., Christensen, F. E., Craig, W. W., Fabian,

A. C., Hailey, C. J., Hornschemeier, A., Kaspi, V., Kulkarni, S. R., Maccarone, T., Miller,

J. M., Rana, V., Stern, D., Tendulkar, S. P., Tomsick, J., Webb, N. A., and Zhang, W. W. (2014). An ultraluminous X-ray source powered by an accreting neutron star. Nature, 514(7521):202–204.

Barrows, R. S., Mezcua, M., and Comerford, J. M. (2019). A catalog of hyper-luminous x-ray sources and intermediate-mass black hole candidates out to high redshifts. The Astrophysical Journal, 882(2):181.

Beall, J. H. (1979). An upper limit for the total energy of relativistic particles contained in the early stages of supernova explosions. The Astrophysical Journal, 230:713–716.

Belczynski, K., Bulik, T., Fryer, C. L., Ruiter, A., Valsecchi, F., Vink, J. S., and Hurley, J. R. (2010). ON THE MAXIMUM MASS OF STELLAR BLACK HOLES. The Astrophysical Journal, 714(2):1217–1226.

Belczynski, K., Hirschi, R., Kaiser, E. A., Liu, J., Casares, J., Lu, Y., O’Shaughnessy, R., Heger, A., Justham, S., and Soria, R. (2020). The formation of a 70 m 。 black hole at high metallicity. The Astrophysical Journal, 890(2):113.92

Bondi, H. (1952). On Spherically Symmetrical Accretion. Monthly Notices of the Royal Astronomical Society, 112(2):195–204.

Brandt, W. N., Alexander, D. M., Hornschemeier, A. E., Garmire, G. P., Schneider, D. P., Barger, A. J., Bauer, F. E., Broos, P. S., Cowie, L. L., Townsley, L. K., Burrows, D. N., Chartas, G., Feigelson, E. D., Griffiths, R. E., Nousek, J. A., and Sargent, W. L. W. (2001). The chandra deep field north survey. v. 1 m[CLC]s[/CLC] source catalogs. The Astronomical Journal, 122(6):2810–2832.

Bruzual, G. and Charlot, S. (2003). Stellar population synthesis at the resolution of 2003. Monthly Notices of the Royal Astronomical Society, 344(4):1000–1028.

Cardelli, J. A., Clayton, G. C., and Mathis, J. S. (1989). The Relationship between Infrared, Optical, and Ultraviolet Extinction. The Astrophysical Journal, 345:245.

Cash, W. (1979). Parameter estimation in astronomy through application of the likelihood ratio. The Astrophysical Journal, 228:939–947.

Chabrier, G. (2003). Galactic stellar and substellar initial mass function. Publications of the Astronomical Society of the Pacific, 115(809):763–795.

Chandra, P., Chevalier, R. A., Chugai, N., Fransson, C., and Soderberg, A. M. (2015). X-RAY AND RADIO EMISSION FROM TYPE IIn SUPERNOVA SN 2010jl. The Astrophysical Journal, 810(1):32.

Charlot, S. and Fall, S. M. (2000). A simple model for the absorption of starlight by dust in galaxies. The Astrophysical Journal, 539(2):718–731.

Colbert, E. J. M., Heckman, T. M., Ptak, A. F., Strickland, D. K., and Weaver, K. A. (2004). Old and young x-ray point source populations in nearby galaxies. The Astrophysical Journal, 602(1):231–248.

Cseh, D., Kaaret, P., Corbel, S., Grisé, F., Lang, C., Körding, E., Falcke, H., Jonker, P. G., Miller-Jones, J. C. A., Farrell, S., Yang, Y. J., Paragi, Z., and Frey, S. (2014). Unveiling recurrent jets of the ULX Holmberg II X-1: evidence for a massive stellar-mass black hole? Monthly Notices of the Royal Astronomical Society: Letters, 439(1):L1–L5.

Da Cunha, E., Charlot, S., and Elbaz, D. (2008). A simple model to interpret the ultraviolet, optical and infrared emission from galaxies. Monthly Notices of the Royal Astronomical Society, 388(4):1595–1617.

Dale, D. A., Bendo, G. J., Engelbracht, C. W., Gordon, K. D., Regan, M. W., Armus, L.,

Cannon, J. M., Calzetti, D., Draine, B. T., Helou, G., Joseph, R. D., Kennicutt, R. C., Li, A., Murphy, E. J., Roussel, H., Walter, F., Hanson, H. M., Hollenbach, D. J., Jarrett, T. H., Kewley, L. J., Lamanna, C. A., Leitherer, C., Meyer, M. J., Rieke, G. H., Rieke, M. J., Sheth, K., Smith, J. D. T., and Thornley, M. D. (2005). Infrared spectral energy distributions of nearby galaxies. The Astrophysical Journal, 633(2):857–870.

de Vaucouleurs, G., de Vaucouleurs, A., Corwin, Herold G., J., Buta, R. J., Paturel, G., and Fouque, P. (1991). Third Reference Catalogue of Bright Galaxies.

Dickey, J. M. and Lockman, F. J. (1990). H i in the galaxy. Annual Review of Astronomy and Astrophysics, 28(1):215–259.

Doi, M., Tanaka, M., Fukugita, M., Gunn, J. E., Yasuda, N., Ivezić, Ž., Brinkmann, J., de Haars, E., Kleinman, S. J., Krzesinski, J., and Leger, R. F. (2010). PHOTOMETRIC RESPONSE FUNCTIONS OF THE SLOAN DIGITAL SKY SURVEY IMAGER. The Astronomical Journal, 139(4):1628–1648.

Farrell, S. A., Webb, N. A., Barret, D., Godet, O., and Rodrigues, J. M. (2009). An intermediate-mass black hole of over 500 solar masses in the galaxy ESO243-49. Nature, 460(7251):73–75.

Fazio, G. G., Hora, J. L., Allen, L. E., Ashby, M. L. N., Barmby, P., Deutsch, L. K., Huang, J.-S., Kleiner, S., Marengo, M., Megeath, S. T., Melnick, G. J., Pahre, M. A., Patten,
B. M., Polizotti, J., Smith, H. A., Taylor, R. S., Wang, Z., Willner, S. P., Hoffmann, W. F., Pipher, J. L., Forrest, W. J., McMurty, C. W., McCreight, C. R., McKelvey, M. E., McMurray, R. E., Koch, D. G., Moseley, S. H., Arendt, R. G., Mentzell, J. E., Marx, C. T., Losch, P., Mayman, P., Eichhorn, W., Krebs, D., Jhabvala, M., Gezari, D. Y., Fixsen, D. J., Flores, J., Shakoorzadeh, K., Jungo, R., Hakun, C., Workman, L., Karpati, G., Kichak, R., Whitley, R., Mann, S., Tollestrup, E. V., Eisenhardt, P., Stern, D., Gorjian, V., Bhattacharya, B., Carey, S., Nelson, B. O., Glaccum, W. J., Lacy, M., Lowrance, P. J., Laine, S., Reach, W. T., Stauffer, J. A., Surace, J. A., Wilson, G., Wright, E. L., Hoffman, A., Domingo, G., and Cohen, M. (2004). The infrared array camera (IRAC) for the spitzer space telescope. The Astrophysical Journal Supplement Series, 154(1):10–17.

Feng, H. and Soria, R. (2011). Ultraluminous x-ray sources in the chandra and xmm-newton era. New Astronomy Reviews, 55(5):166 – 183.

Frank, J., King, A., and Raine, D. (2002). Accretion Power in Astrophysics. Cambridge University Press, 3 edition.

Freeman, P., Doe, S., and Siemiginowska, A. (2001). Sherpa: a mission-independent data analysis application. In Starck, J.-L. and Murtagh, F. D., editors, Astronomical Data Analysis, volume 4477, pages 76 – 87. International Society for Optics and Photonics, SPIE.

Fruscione, A., McDowell, J. C., Allen, G. E., Brickhouse, N. S., Burke, D. J., Davis, J. E., Durham, N., Elvis, M., Galle, E. C., Harris, D. E., Huenemoerder, D. P., Houck, J. C., Ishibashi, B., Karovska, M., Nicastro, F., Noble, M. S., Nowak, M. A., Primini, F. A., Siemiginowska, A., Smith, R. K., and Wise, M. (2006). CIAO: Chandra’s data analysis system. In Silva, D. R. and Doxsey, R. E., editors, Observatory Operations: Strategies, Processes, and Systems, volume 6270, pages 586 – 597. International Society for Optics and Photonics, SPIE.

Fryer, C. L. and Kalogera, V. (2001). Theoretical black hole mass distributions. The Astrophysical Journal, 554(1):548–560.

Gebhardt, K., Rich, R. M., and Ho, L. C. (2002). A 20,000 [ITAL]m[/ITAL][TINF]。[/TINF] black hole in the stellar cluster g1. The Astrophysical Journal, 578(1):L41–L45.

Gebhardt, K., Rich, R. M., and Ho, L. C. (2005). An intermediate-mass black hole in the globular cluster g1: Improved significance from new keck andHubble space Tele- scopeObservations. The Astrophysical Journal, 634(2):1093–1102.

Gehrz, R. D., Roellig, T. L., Werner, M. W., Fazio, G. G., Houck, J. R., Low, F. J., Rieke, G. H., Soifer, B. T., Levine, D. A., and Romana, E. A. (2007). The nasa spitzer space telescope. Review of Scientific Instruments, 78(1):011302.

Gelman, A., Carlin, J., Stern, H., Dunson, D., Vehtari, A., and Rubin, D. (2013). Bayesian data analysis third edition. boca raton. FL: CRC Press.[Google Scholar].

Gendreau, K. C., Barcons, X., and Fabian, A. C. (1998). Deep hard X-ray source counts from a fluctuation analysis of ASCA SIS images. Monthly Notices of the Royal Astronomical Society, 297(1):41–48.

Giacconi, R., Rosati, P., Tozzi, P., Nonino, M., Hasinger, G., Norman, C., Bergeron, J., Borgani, S., Gilli, R., Gilmozzi, R., and Zheng, W. (2001). First results from the x-ray and optical survey of theChandraDeep field south. The Astrophysical Journal, 551(2):624–634.

Gladstone, J. C., Copperwheat, C., Heinke, C. O., Roberts, T. P., Cartwright, T. F., Levan, A. J., and Goad, M. R. (2013). OPTICAL COUNTERPARTS OF THE NEAREST ULTRALUMINOUS x-RAY SOURCES. The Astrophysical Journal Supplement Series, 206(2):14.

Grimm, H.-J., Gilfanov, M., and Sunyaev, R. (2002). The milky way in x-rays for an outside observer - log(n)-log(s) and luminosity function of x-ray binaries from rxte/asm data. Astronomy and Astrophysics, 391(3):923–944.

Grimm, H.-J., Gilfanov, M., and Sunyaev, R. (2003). High-mass X-ray binaries as a star formation rate indicator in distant galaxies. Monthly Notices of the Royal Astronomical Society, 339(3):793–809.

Hasinger, G., Burg, R., Giacconi, R., Hartner, G., Schmidt, M., Trumper, J., and Zamorani, G. (1993). A deep X-ray survey in the Lockman hole and the soft X-ray log N-log S. Astronomy and Astrophysics, 275:1–15.

Hasinger, G., Giacconi, R., Gunn, J. E., Lehmann, I., Schmidt, M., Schneider, D. P., Truemper, J., Wambsganss, J., Woods, D., and Zamorani, G. (1998). The ROSAT Deep Survey. IV. A distant lensing cluster of galaxies with a bright arc. Astronomy and Astrophysics, 340:L27–L30.

Heger, A., Fryer, C. L., Woosley, S. E., Langer, N., and Hartmann, D. H. (2003). How massive single stars end their life. The Astrophysical Journal, 591(1):288–300.

Heikkilä, T., Tsygankov, S., Mattila, S., Eldridge, J. J., Fraser, M., and Poutanen, J. (2016). Progenitor constraints for core-collapse supernovae from Chandra X-ray observations. Monthly Notices of the Royal Astronomical Society, 457(1):1107–1123.

Heil, L. M., Vaughan, S., and Roberts, T. P. (2009). A systematic study of variability in a sample of ultraluminous X-ray sources. Monthly Notices of the Royal Astronomical Society, 397(2):1061–1072.

Holincheck, A. J., Wallin, J. F., Borne, K., Fortson, L., Lintott, C., Smith, A. M., Bamford, S., Keel, W. C., and Parrish, M. (2016). Galaxy Zoo: Mergers – Dynamical models of interacting galaxies. Monthly Notices of the Royal Astronomical Society, 459(1):720–745.

Hu, C.-P., Kong, A. K. H., Ng, C.-Y., and Li, K. L. (2018). NGC 7793 p9: An ultraluminous x-ray source evolved from a canonical black hole x-ray binary. The Astrophysical Journal, 864(1):64.

Israel, G. L., Belfiore, A., Stella, L., Esposito, P., Casella, P., De Luca, A., Marelli, M., Papitto, A., Perri, M., Puccetti, S., Castillo, G. A. R., Salvetti, D., Tiengo, A., Zampieri, L., D’Agostino, D., Greiner, J., Haberl, F., Novara, G., Salvaterra, R., Turolla, R., Watson,

M., Wilms, J., and Wolter, A. (2017). An accreting pulsar with extreme properties drives an ultraluminous x-ray source in NGC 5907. Science, 355(6327):817–819.

Israel, G. L., Papitto, A., Esposito, P., Stella, L., Zampieri, L., Belfiore, A., Rodríguez Castillo, G. A., De Luca, A., Tiengo, A., Haberl, F., Greiner, J., Salvaterra, R., Sandrelli, S., and Lisini, G. (2016). Discovery of a 0.42-s pulsar in the ultraluminous X-ray source NGC 7793 P13. Monthly Notices of the Royal Astronomical Society: Letters, 466(1):L48–L52.

Kaaret, P., Feng, H., and Roberts, T. P. (2017). Ultraluminous x-ray sources. Annual Review of Astronomy and Astrophysics, 55(1):303–341.

Kato, S., Fukue, J., and Mineshige, S. (2008). Black-Hole Accretion Disks — Towards a New Paradigm —.

Kennicutt, Robert C., J., Armus, L., Bendo, G., Calzetti, D., Dale, D. A., Draine, B. T., Engelbracht, C. W., Gordon, K. D., Grauer, A. D., Helou, G., Hollenbach, D. J., Jarrett,


T. H., Kewley, L. J., Leitherer, C., Li, A., Malhotra, S., Regan, M. W., Rieke, G. H., Rieke, M. J., Roussel, H., Smith, J.-D. T., Thornley, M. D., and Walter, F. (2003). SINGS: TheSIRTFNearby galaxies survey. Publications of the Astronomical Society of the Pacific, 115(810):928–952.

King, A. R., Davies, M. B., Ward, M. J., Fabbiano, G., and Elvis, M. (2001). Ultraluminous x-ray sources in external galaxies. The Astrophysical Journal, 552(2):L109–L112.

King, A. R. and Dehnen, W. (2005). Hierarchical merging, ultraluminous and hyperluminous X-ray sources. Monthly Notices of the Royal Astronomical Society, 357(1):275–278.

Kitaki, T., Mineshige, S., Ohsuga, K., and Kawashima, T. (2017). Theoretical modeling of Comptonized X-ray spectra of super-Eddington accretion flow: Origin of hard excess in ultraluminous X-ray sources. Publications of the Astronomical Society of Japan, 69(6). 92.

Kong, A. K. H. and Stefano, R. D. (2005). An unusual spectral state of an ultraluminous very soft x-ray source during outburst. The Astrophysical Journal, 632(2):L107–L110.

Kouroumpatzakis, K., Zezas, A., Sell, P., Kovlakas, K., Bonfini, P., Willner, S. P., Ashby, M. L. N., Maragkoudakis, A., and Jarrett, T. H. (2020). Sub-galactic scaling relations between X-ray luminosity, star formation rate, and stellar mass. Monthly Notices of the Royal Astronomical Society, 494(4):5967–5984.

Lau, R. M., Heida, M., Walton, D. J., Kasliwal, M. M., Adams, S. M., Cody, A. M., De, K., Gehrz, R. D., Fürst, F., Jencson, J. E., Kennea, J. A., and Masci, F. (2019). Uncovering red and dusty ultraluminous x-ray sources withSpitzer. The Astrophysical Journal, 878(1):71.

Lin, L. C.-C., Hu, C.-P., Kong, A. K. H., Yen, D. C.-C., Takata, J., and Chou, Y. (2015). Long-term X-ray variability of ultraluminous X-ray sources. Monthly Notices of the Royal Astronomical Society, 454(2):1644–1657.

Liu, J.-F., Bregman, J. N., Bai, Y., Justham, S., and Crowther, P. (2013). Puzzling accretion onto a black hole in the ultraluminous X-ray source M 101 ULX-1. Nature, 503(7477):500–503.

Luangtip, W., Roberts, T. P., Mineo, S., Lehmer, B. D., Alexander, D. M., Jackson, F. E., Goulding, A. D., and Fischer, J. L. (2014). A deficit of ultraluminous X-ray sources in luminous infrared galaxies. Monthly Notices of the Royal Astronomical Society, 446(1):470– 492.

Luo, B., Brandt, W. N., Xue, Y. Q., Lehmer, B., Alexander, D. M., Bauer, F. E., Vito, F., Yang, G., Basu-Zych, A. R., Comastri, A., Gilli, R., Gu, Q.-S., Hornschemeier, A. E., Koekemoer, A., Liu, T., Mainieri, V., Paolillo, M., Ranalli, P., Rosati, P., Schneider, D. P., Shemmer, O., Smail, I., Sun, M., Tozzi, P., Vignali, C., and Wang, J.-X. (2016). THE CHANDRA DEEP FIELD-SOUTH SURVEY: 7 MS SOURCE CATALOGS. The Astrophysical Journal Supplement Series, 228(1):2.

López, K. M., Jonker, P. G., Heida, M., Torres, M. A. P., Roberts, T. P., Walton, D., Moon, D.-S., and Harrison, F. A. (2019). Discovery and analysis of a ULX nebula in NGC 3521. Monthly Notices of the Royal Astronomical Society, 489(1):1249–1264.

Madau, P. and Rees, M. J. (2001). Massive black holes as population III remnants. The Astrophysical Journal, 551(1):L27–L30.

Mapelli, M., Ripamonti, E., Zampieri, L., Colpi, M., and Bressan, A. (2010). Ultra-luminous X-ray sources and remnants of massive metal-poor stars. Monthly Notices of the Royal Astronomical Society, 408(1):234–253.

Mezcua, M., Lobanov, A. P., Mediavilla, E., and Karouzos, M. (2014). PHOTOMETRIC DECOMPOSITION OF MERGERS IN DISK GALAXIES. The Astrophysical Journal, 784(1):16.

Miller, J. M., Fabian, A. C., and Miller, M. C. (2004). A comparison of intermediate-mass black hole candidate ultraluminous x-ray sources and stellar-mass black holes. The Astrophysical Journal, 614(2):L117–L120.

Miller, M. C. and Colbert, E. J. M. (2004). Intermediate-Mass Black Holes. International Journal of Modern Physics D, 13(1):1–64.

Mineo, S., Gilfanov, M., and Sunyaev, R. (2012). X-ray emission from star-forming galaxies – I. High-mass X-ray binaries. Monthly Notices of the Royal Astronomical Society, 419(3):2095–2115.

Mineo, S., Rappaport, S., Levine, A., Pooley, D., Steinhorn, B., and Homan, J. (2014). A COMPREHENSIVE x-RAY AND MULTIWAVELENGTH STUDY OF THE COLLIDING GALAXY PAIR NGC 2207/IC 2163. The Astrophysical Journal, 797(2):91.

Mitsuda, K., Inoue, H., Koyama, K., Makishima, K., Matsuoka, M., Ogawara, Y., Shibazaki, N., Suzuki, K., Tanaka, Y., and Hirano, T. (1984). Energy spectra of low-mass binary X-ray sources observed from Tenma. Publications of the Astronomical Society of Japan, 36:741–759.

Nelder, J. A. and Mead, R. (1965). A Simplex Method for Function Minimization. The Computer Journal, 7(4):308–313.

Ogasaka, Y., Kii, T., Ueda, Y., Takahashi, T., Yamada, T., Inoue, H., Ishisaki, Y., Ohta, K., Makishima, K., Miyaji, T., and Hasinger, G. (1998). Sky surveys with ASCA — Deep Sky Survey. Astronomische Nachrichten, 319(1):43.

Peeters, E., Spoon, H. W. W., and Tielens, A. G. G. M. (2004). Polycyclic aromatic hydrocarbons as a tracer of star formation? The Astrophysical Journal, 613(2):986– 1003.

Poutanen, J., Lipunova, G., Fabrika, S., Butkevich, A. G., and Abolmasov, P. (2007). Supercritically accreting stellar mass black holes as ultraluminous X-ray sources. Monthly Notices of the Royal Astronomical Society, 377(3):1187–1194.

Prestwich, A. H., Irwin, J. A., Kilgard, R. E., Krauss, M. I., Zezas, A., Primini, F., Kaaret, P., and Boroson, B. (2003). Classifying x-ray sources in external galaxies from x-ray colors. The Astrophysical Journal, 595(2):719–726.

Remillard, R. A. and McClintock, J. E. (2006). X-ray properties of black-hole binaries. Annual Review of Astronomy and Astrophysics, 44(1):49–92.

Roberts, T. P., Warwick, R. S., Ward, M. J., and Murray, S. S. (2002). A Chandra observation of the interacting pair of galaxies NGC 4485/44901. Monthly Notices of the Royal Astronomical Society, 337(2):677–692.

Sathyaprakash, R., Roberts, T. P., and Siwek, M. M. (2019). Observational limits on the X-ray emission from the bubble nebula surrounding Ho IX X-1. Monthly Notices of the Royal Astronomical Society, 488(4):4614–4622.

Schlegel, D. J., Finkbeiner, D. P., and Davis, M. (1998). Maps of dust infrared emission for use in estimation of reddening and cosmic microwave background radiation foregrounds. The Astrophysical Journal, 500(2):525–553.

Schlegel, E. M. (1995). X-ray emission from supernovae: a review of the observations. Reports on Progress in Physics, 58(11):1375–1413.

Shakura, N. I. and Sunyaev, R. A. (1973). Reprint of 1973A&A....24..337S. Black holes in binary systems. Observational appearance. Astronomy and Astrophysics, 500:33–51.

Siemiginowska, A., Kashyap, V., Refsdal, B., van Dyk, D., Connors, A., and Park, T. (2011). pyblocxs: Bayesian Low-Counts X-ray Spectral Analysis in Sherpa. In Evans,

I. N., Accomazzi, A., Mink, D. J., and Rots, A. H., editors, Astronomical Data Analysis Software and Systems XX, volume 442 of Astronomical Society of the Pacific Conference Series, page 439.

Smith, B. J., Campbell, K., Struck, C., Soria, R., Swartz, D., Magno, M., Dunn, B., and Giroux, M. L. (2018). Diffuse x-ray-emitting gas in major mergers. The Astronomical Journal, 155(2):81.

Smith, B. J., Swartz, D. A., Miller, O., Burleson, J. A., Nowak, M. A., and Struck, C. (2012). ChAInGeS: THECHANDRAARP INTERACTING GALAXIES SURVEY. The Astronomical Journal, 143(6):144.

Smith, N. (2014). Mass loss: Its effect on the evolution and fate of high-mass stars. Annual Review of Astronomy and Astrophysics, 52(1):487–528.

Song, X., Walton, D. J., Lansbury, G. B., Evans, P. A., Fabian, A. C., Earnshaw, H., and Roberts, T. P. (2019). The hunt for pulsating ultraluminous X-ray sources. Monthly Notices of the Royal Astronomical Society, 491(1):1260–1277.

Soria, R. and Motch, C. (2004). A variable ultra-luminous x-ray source in the colliding galaxy ngc4. Astronomy and Astrophysics, 422(3):915–923.

Steiner, J. F., Narayan, R., McClintock, J. E., and Ebisawa, K. (2009). A simple comptonization model. Publications of the Astronomical Society of the Pacific, 121(885):1279–1290.

Sutton, A. D., Roberts, T. P., and Middleton, M. J. (2013). The ultraluminous state revisited: fractional variability and spectral shape as diagnostics of super-Eddington accretion. Monthly Notices of the Royal Astronomical Society, 435(2):1758–1775.

Sutton, A. D., Roberts, T. P., Walton, D. J., Gladstone, J. C., and Scott, A. E. (2012). The most extreme ultraluminous X-ray sources: evidence for intermediate-mass black holes? Monthly Notices of the Royal Astronomical Society, 423(2):1154–1177.

Swartz, D. A., Ghosh, K. K., Tennant, A. F., and Wu, K. (2004). The ultraluminous x-ray source population from the chandra archive of galaxies. The Astrophysical Journal Supplement Series, 154(2):519–539.

Swartz, D. A., Soria, R., Tennant, A. F., and Yukita, M. (2011). A COMPLETE SAMPLE OF ULTRALUMINOUS x-RAY SOURCE HOST GALAXIES. The Astrophysical Journal, 741(1):49.

Swartz, D. A., Tennant, A. F., and Soria, R. (2009). ULTRALUMINOUS x-RAY SOURCE CORRELATIONS WITH STAR-FORMING REGIONS. The Astrophysical Journal, 703(1):159–168.

Tauris, T. M. and van den Heuvel, E. P. J. (2006). Formation and evolution of compact stellar X-ray sources, volume 39, pages 623–665.

Ueda, Y., Takahashi, T., Inoue, H., Tsuru, T., Sakano, M., Ishisaki, Y., Ogasaka, Y., Makishima, K., Yamada, T., Ohta, K., and Akiyama, M. (1998). A population of faint galaxies that contribute to the cosmic X-ray background. Nature, 391(6670):866–868.

van Dyk, D. A., Connors, A., Kashyap, V. L., and Siemiginowska, A. (2001). Analysis of energy spectra with low photon counts via bayesian posterior simulation. The Astrophysical Journal, 548(1):224–243.

Vink, J. (2016). X-Ray Emission Properties of Supernova Remnants, pages 1–24. Springer International Publishing, Cham.

Walton, D. J., Roberts, T. P., Mateos, S., and Heard, V. (2011). 2XMM ultraluminous X-ray source candidates in nearby galaxies. Monthly Notices of the Royal Astronomical Society, 416(3):1844–1861.

Wenger, M., Ochsenbein, F., Egret, D., Dubois, P., Bonnarel, F., Borde, S., Genova, F., Jasniewicz, G., Laloë, S., Lesteven, S., and Monier, R. (2000). The simbad astronomical database - the cds reference database for astronomical objects. Astron. Astrophys. Suppl. Ser., 143(1):9–22.

Wolter, A., Fruscione, A., and Mapelli, M. (2018). The x-ray luminosity function of ultraluminous x-ray sources in collisional ring galaxies. The Astrophysical Journal, 863(1):43.

Wu, H., Cao, C., Hao, C.-N., Liu, F.-S., Wang, J.-L., Xia, X.-Y., Deng, Z.-G., and Young, C. K.-S. (2005). PAH and mid-infrared luminosities as measures of star formation rate in spitzer first look survey galaxies. The Astrophysical Journal, 632(2):L79–L82.

Yuan, F.-T., Argudo-Fernández, María, Shen, Shiyin, Hao, Lei, Jiang, Chunyan, Yin, Jun, Boquien, Médéric, and Lin, Lihwai (2018). Spatially resolved star formation and dust attenuation in mrk 848: Comparison of the integral field spectra and the uv-to-ir sed. Astronomy and Astrophysics, 613:A13.

Zezas, A. and Fabbiano, G. (2002). ChandraObservations of “the antennae” galaxies (NGC 4038/4039). IV. the x-ray source luminosity function and the nature of ultraluminous x-ray sources. The Astrophysical Journal, 577(2):726–737.

Zhu, Y.-N., Wu, H., Li, H.-N., and Cao, C. (2010). Stellar mass estimation based on IRAC photometry for Spitzer SWIRE-field galaxies. Research in Astronomy and Astrophysics, 10(4):329–347.