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26 April 2024 |
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The Nature of Blue Cores in Spheroids: a Possible Connection with AGN and Star Formation | | Felipe Menanteau
; Andre R. Martel
; Paolo Tozzi
; Brenda Frye
; Holland C. Ford
; Leopoldo Infante
; Narciso Benitez
; Gaspar Galaz
; Daniel Coe
; Garth D. Illingworth
; George F. Hartig
; Marc Clampin
; | | Date: |
5 Nov 2004 | | Journal: | Astrophys.J. 620 (2005) 697-702 | | Subject: | astro-ph | | Abstract: | We investigate the physical nature of blue cores in early-type galaxies through the first multi-wavelength analysis of a serendipitously discovered field blue-nucleated spheroid in the background of the deep ACS/WFC griz multicolor observations of the cluster Abell 1689. The resolved g-r, r-i and i-z color maps reveal a prominent blue core identifying this galaxy as a ``typical’’ case study, exhibiting variations of 0.5-1.0 mag in color between the center and the outer regions, opposite to the expectations of reddened metallicity induced gradients in passively evolved ellipticals. From a Magellan-Clay spectrum we secure the galaxy redshift at $z=0.624$. We find a strong X-ray source coincident with the spheroid galaxy. Spectral features and a high X-ray luminosity indicate the presence of an AGN in the galaxy. However, a comparison of the X-ray luminosity to a sample derived from the Chandra Deep Field South displays Lx to be comparable to Type I/QSO galaxies while the optical flux is consistent with a normal star-forming galaxy. We conclude that the galaxy’s non-thermal component dominates at high-energy wavelengths while we associate the spheroid blue light with the stellar spectrum of normal star-forming galaxies. We argue about a probable association between the presence of blue cores in spheroids and AGN activity. | | Source: | arXiv, astro-ph/0411125 | | Services: | Forum | Review | PDF | Favorites | |
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