Browsing by Author "Khan, Sophia A."

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    A SPITZER-SELECTED GALAXY CLUSTER AT z=1.62
    (2010) Papovich, C.; Khan, Sophia A.
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    ON THE NATURE OF THE FIRST GALAXIES SELECTED AT 350 mu m
    (IOP PUBLISHING LTD, 2009) Khan, Sophia A.; Chanial, Pierre F.; Willner, S. P.; Pearson, Chris P.; Ashby, M. L. N.; Benford, Dominic J.; Clements, David L.; Dye, Simon; Farrah, Duncan; Fazio, G. G.; Huang, J. S.; Lebouteiller, V.; Le Floc'h, Emeric; Mainetti, Gabriele; Moseley, S. Harvey; Negrello, Mattia; Serjeant, Stephen; Shafer, Richard A.; Staguhn, Johannes; Sumner, Timothy J.; Vaccari, Mattia
    We present constraints on the nature of the first galaxies selected at 350 mu m. The sample includes galaxies discovered in the deepest blank-field survey at 350 mu m (in the Bootes Deep Field) and also later serendipitous detections in the Lockman Hole. In determining multiwavelength identifications, the 350 mu m position and map resolution of the second generation Submillimeter High Angular Resolution Camera are critical, especially in the cases where multiple radio sources exist and the 24 mu m counterparts are unresolved. Spectral energy distribution templates are fitted to identified counterparts, and the sample is found to comprise IR-luminous galaxies at 1 < z < 3 predominantly powered by star formation. The first spectrum of a 350 mu m selected galaxy provides an additional confirmation, showing prominent dust grain features typically associated with star-forming galaxies. Compared to submillimeter galaxies selected at 850 and 1100 mu m, galaxies selected at 350 mu m have a similar range of far-infrared color temperatures. However, no 350 mu m selected sources are reliably detected at 850 or 1100 mu m. Galaxies in our sample with redshifts 1 < z < 2 show a tight correlation between the far-and mid-infrared flux densities, but galaxies at higher redshifts show a large dispersion in their mid-to far-infrared colors. This implies a limit to which the mid-IR emission traces the far-IR emission in star-forming galaxies. The 350 mu m flux densities (15 < S(350) < 40 mJy) place these objects near the Herschel/SPIRE 350 mu m confusion threshold, with the lower limit on the star formation rate density suggesting the bulk of the 350 mu m contribution will come from less luminous infrared sources and normal galaxies. Therefore, the nature of the dominant source of the 350 mu m background-star-forming galaxies in the epoch of peak star formation in the universe-could be more effectively probed using ground-based instruments with their angular resolution and sensitivity offering significant advantages over space-based imaging.
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    Spectroscopically and spatially resolved optical line emission in the Superantennae (IRAS 19254-7245)
    (2009) Bendo, George J.; Clements, David L.; Khan, Sophia A.
    We present Visible Multi-Object Spectrograph integral-field spectroscopic observations of the ultraluminous infrared galaxy (ULIRG) pair IRAS 19254-7245 (the Superantennae). We resolveH alpha, [N II], [O I] and [S II] emission both spatially and spectroscopically, and separate the emission into multiple velocity components. We identify spectral line emission characteristic of star formation associated with both galaxies, broad spectral line emission from the nucleus of the southern progenitor and potential outflows with shock-excited spectral features near both nuclei. We estimate that less than or similar to 10 per cent of the 24 mu m flux density originates from star formation, implying that most of the 24 mu m emission originates from the active galactic nuclei in the southern nucleus. We also measure a gas consumption time of similar to 1 Gyr, which is consistent with other measurements of ULIRGs.