VTechWorks staff will be away for the Thanksgiving holiday starting at noon on Wednesday, November 23, through Friday, November 25, and will not be replying to requests during this time. Thank you for your patience.
UV-bright nearby early-type galaxies observed in the mid-infrared: evidence for a multi-stage formation history by way of WISE and GALEX imaging
Petty, S. M.
Neill, J. D.
Jarrett, T. H.
Blain, A. W.
Rich, R. M.
Tsai, C. W.
Benford, D. J.
Bridge, C. R.
Lake, S. E.
Masci, F. J.
Wright, E. L.
MetadataShow full item record
In the local universe, 10% of massive elliptical galaxies are observed to exhibit a peculiar property: a substantial excess of ultraviolet emission than what is expected from their old, red stellar populations. Several origins for this ultraviolet excess (UVX) have been proposed including a population of hot young stars and a population of old, blue horizontal branch or extended horizontal branch (BHB or EHB) stars that have undergone substantial mass loss from their outer atmospheres. We explore the radial distribution of UVX in a selection of 49 nearby E/S0-type galaxies by measuring their extended photometry in the UV through mid-infrared (mid-IR) with the Galaxy Evolution Explorer (GALEX), the Sloan Digital Sky Survey, and the Wide-field Infrared Survey Explorer (WISE). We compare UV/optical and UV/mid-IR colors with the Flexible Stellar Population Synthesis models, which allow for the inclusion of EHB stars. We find that combined WISE mid-IR and GALEX UV colors are more effective in distinguishing models than optical colors, and that the UV/mid-IR combination is sensitive to the EHB fraction. There are strong color gradients, with the outer radii bluer than the inner half-light radii by similar to 1 mag. This color difference is easily accounted for with an increase in the BHB fraction of 0.25 with radius. We estimated that the average ages for the inner and outer radii are 7.0 +/- 0.3 Gyr, and 6.2 +/- 0.2 Gyr, respectively, with the implication that the outer regions are likely to have formed similar to 1 Gyr after the inner regions. Additionally, we find that metallicity gradients are likely not a significant factor in the color difference. The separation of color between the inner and outer regions, which agrees with a specific stellar population difference (e. g., higher EHB populations), and the similar to 0.5-2 Gyr age difference suggests multi-stage formation. Our results are best explained by inside-out formation: rapid star formation within the core at early epochs (>4 Gyr ago) and at least one later stage starburst event coinciding with z similar to 1.
Showing items related by title, author, creator and subject.
Casey, C. M.; Berta, S.; Bethermin, M.; Bock, J.; Bridge, C. R.; Burgarella, D.; Chapin, E.; Chapman, S. C.; Clements, D. L.; Conley, A.; Conselice, C. J.; Cooray, A.; Farrah, D.; Hatziminaoglou, E.; Ivison, R. J.; Le Floc'h, E.; Lutz, D.; Magdis, G. E.; Magnelli, B.; Oliver, S. J.; Page, M. J.; Pozzi, F.; Rigopoulou, D.; Riguccini, L.; Roseboom, I. G.; Sanders, D. B.; Scott, D.; Seymour, N.; Valtchanov, I.; Vieira, J. D.; Viero, M.; Wardlow, J. (IOP Publishing Ltd., 2012-12)We present spectroscopic observations for a sample of 36 Herschel-Spire 250-500 mu m selected galaxies (HSGs) at 2 < z < 5 from the Herschel Multi-tiered Extragalactic Survey. Redshifts are confirmed as part of a large ...
Ivison, R. J.; Swinbank, A. M.; Smail, I.; Harris, A. I.; Bussmann, R. S.; Cooray, A.; Cox, P.; Fu, H.; Kovacs, A.; Krips, M.; Narayanan, D.; Negrello, M.; Neri, R.; Penarrubia, J.; Richard, J.; Riechers, D. A.; Rowlands, K.; Staguhn, J. G.; Targett, T. A.; Amber, S.; Baker, A. J.; Bourne, N.; Bertoldi, F.; Bremer, M.; Calanog, J. A.; Clements, D. L.; Dannerbauer, H.; Dariush, A.; De Zotti, G.; Dunne, L.; Eales, S. A.; Farrah, D.; Fleuren, S.; Franceschini, A.; Geach, J. E.; George, R. D.; Helly, J. C.; Hopwood, R.; Ibar, E.; Jarvis, M. J.; Kneib, J. P.; Maddox, S.; Omont, A.; Scott, D.; Serjeant, S.; Smith, M. W. L.; Thompson, M. A.; Valiante, E.; Valtchanov, I.; Vieira, J.; van der Werf, P. (IOP PUBLISHING LTD, 2013-08)Panchromatic observations of the best candidate hyperluminous infrared galaxies from the widest Herschel extragalactic imaging survey have led to the discovery of at least four intrinsically luminous z = 2.41 galaxies ...
Santini, P.; Maiolino, R.; Magnelli, B.; Lutz, D.; Lamastra, A.; Causi, G. L.; Eales, S.; Andreani, P.; Berta, S.; Buat, V.; Cooray, A.; Cresci, G.; Daddi, E.; Farrah, D.; Fontana, A.; Franceschini, A.; Genzel, R.; Granato, G.; Grazian, A.; Le Floc'h, E.; Magdis, G. E.; Magliocchetti, M.; Mannucci, F.; Menci, N.; Nordon, R.; Oliver, S.; Popesso, P.; Pozzi, F.; Riguccini, L.; Rodighiero, G.; Rosario, D. J.; Salvato, M.; Scott, D.; Silva, L.; Tacconi, L.; Viero, M.; Wang, L.; Wuyts, S.; Xu, K. (EDP SCIENCES, 2014-02)We use deep Herschel observations taken with both PACS and SPIRE imaging cameras to estimate the dust mass of a sample of galaxies extracted from the GOODS-S, GOODS-N and the COSMOS fields. We divide the redshift-stellar ...