Journal
ASTROPHYSICAL JOURNAL
Volume 785, Issue 2, Pages -Publisher
IOP PUBLISHING LTD
DOI: 10.1088/0004-637X/785/2/147
Keywords
galaxies: individual (NGC 4472); galaxies: star clusters: individual ( NGC 4472); globular clusters: general; X-rays: binaries; X-rays: galaxies: clusters
Categories
Funding
- NSF [AST-0807557]
- NASA [GO1-12112X, GO0-11111A]
- NSF Faculty Early Career Development grant [AST-0847109]
- Chandra X-Ray Observatory
- Division Of Astronomical Sciences
- Direct For Mathematical & Physical Scien [0847109] Funding Source: National Science Foundation
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We present an analysis of optical spectra from the globular cluster RZ2109 in NGC 4472, which hosts the first unambiguous globular cluster black hole. We use these spectra to determine the elemental composition of the emission line system associated with this source, and to constrain the age and metallicity of the host globular cluster. For the emission line system of RZ2109, our analysis indicates the [O III] lambda 5007 equivalent width is 33.82 +/- 0.39 angstrom and the H beta equivalent width is 0.32 +/- 0.32 angstrom, producing a formal [OIII] lambda 5007/H beta emission line ratio of 106 for a 3200 km s(-1) measurement aperture covering the full velocity width of the [O III] lambda 5007 line. Within a narrower 600 km s(-1) aperture covering the highest luminosity velocity structure in the line complex, we find [O III] lambda 5007/H beta = 62. The measured [O III] lambda 5007/H beta ratios are significantly higher than can be produced in radiative models of the emission line region with solar composition, and the confidence interval limits exclude all but models which have gas masses much larger than those for a single star. Therefore, we conclude that the region from which the [O III] lambda 5007 emission originates is hydrogen-depleted relative to solar composition gas. This finding is consistent with emission from an accretion-powered outflow driven by a hydrogen-depleted donor star, such as a white dwarf, being accreted onto a black hole.
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