Browsing by Author "Clements, David L."

Now showing 1 - 4 of 4
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    Characterization of Two 2 mm detected Optically Obscured Dusty Star-forming Galaxies
    (2022) Manning, Sinclaire M.; Casey, Caitlin M.; Zavala, Jorge A.; Magdis, Georgios E.; Drew, Patrick M.; Champagne, Jaclyn B.; Aravena, Manuel; Béthermin, Matthieu; Clements, David L.; Finkelstein, Steven L.; Fujimoto, Seiji; Hayward, Christopher C.; Hodge, Jacqueline A.; Ilbert, Olivier; Kartaltepe, Jeyhan S.; Knudsen, Kirsten K.; Koekemoer, Anton M.; Man, Allison W. S.; Sanders, David B.; Sheth, Kartik; Spilker, Justin S.; Staguhn, Johannes; Talia, Margherita; Treister, Ezequiel; Yun, Min S.
    The 2 mm Mapping Obscuration to Reionization with ALMA (MORA) Survey was designed to detect high-redshift (z greater than or similar to 4), massive, dusty star-forming galaxies (DSFGs). Here we present two likely high-redshift sources, identified in the survey, whose physical characteristics are consistent with a class of optical/near-infrared (OIR)-invisible DSFGs found elsewhere in the literature. We first perform a rigorous analysis of all available photometric data to fit spectral energy distributions and estimate redshifts before deriving physical properties based on our findings. Our results suggest the two galaxies, called MORA-5 and MORA-9, represent two extremes of the "OIR-dark" class of DSFGs. MORA-5 (z(phot) = 4.3(-1.3)(+1.5)) is a significantly more active starburst with a star formation rate (SFR) of 830(-190)(+340) M-circle dot yr(-1) compared to MORA-9 (z(phot) = 4.3(-1.0)(+1.3)), whose SFR is a modest 200(-60)(+250) M-circle dot yr(-1). Based on the stellar masses (M-star approximate to 10(10-11) M-circle dot), space density (n similar to (5 +/- 2) x 10(-6) Mpc(-3), which incorporates two other spectroscopically confirmed OIR-dark DSFGs in the MORA sample at z = 4.6 and z = 5.9), and gas depletion timescales (<1 Gyr) of these sources, we find evidence supporting the theory that OIR-dark DSFGs are the progenitors of recently discovered 3 < z < 4 massive quiescent galaxies.
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    Mapping Obscuration to Reionization with ALMA (MORA): 2 mm Efficiently Selects the Highest-redshift Obscured Galaxies
    (2021) Casey, Caitlin M.; Zavala, Jorge A.; Manning, Sinclaire M.; Aravena, Manuel; Béthermin, Matthieu; Caputi, Karina I.; Champagne, Jaclyn B.; Clements, David L.; Drew, Patrick; Finkelstein, Steven L.; Fujimoto, Seiji; Hayward, Christopher C.; Dekel, Anton M.; Kokorev, Vasily; Lagos, Claudia del P.; Long, Arianna S.; Magdis, Georgios E.; Man, Allison W. S.; Mitsuhashi, Ikki; Popping, Gergö; Spilker, Justin; Staguhn, Johannes; Talia, Margherita; Toft, Sune; Treister, Ezequiel; Weaver, John R.; Yun, Min
    We present the characteristics of 2 mm selected sources from the largest Atacama Large Millimeter/submillimeter Array (ALMA) blank-field contiguous survey conducted to date, the Mapping Obscuration to Reionization with ALMA (MORA) survey covering 184 arcmin(2) at 2 mm. Twelve of 13 detections above 5 sigma are attributed to emission from galaxies, 11 of which are dominated by cold dust emission. These sources have a median redshift of < Z(2) (mm)> = 3.6(-0.3)(+0.4) primarily based on optical/near-infrared photometric redshifts with some spectroscopic redshifts, with 77% +/- 11% of sources at z > 3 and 38% +/- 12% of sources at z > 4. This implies that 2 mm selection is an efficient method for identifying the highest-redshift dusty star-forming galaxies (DSFGs). Lower-redshift DSFGs (z < 3) are far more numerous than those at z > 3 yet are likely to drop out at 2 mm. MORA shows that DSFGs with star formation rates in excess of 300 M-circle dot yr(-1) and a relative rarity of similar to 10(-5) Mpc(-3) contribute similar to 30% to the integrated star formation rate density at 3 < z < 6. The volume density of 2 mm selected DSFGs is consistent with predictions from some cosmological simulations and is similar to the volume density of their hypothesized descendants: massive, quiescent galaxies at z > 2. Analysis of MORA sources' spectral energy distributions hint at steeper empirically measured dust emissivity indices than reported in typical literature studies, with = 2.2(-0.4)(+0.5). The MORA survey represents an important step in taking census of obscured star formation in the universe's first few billion years, but larger area 2 mm surveys are needed to more fully characterize this rare population and push to the detection of the universe's first dusty galaxies.
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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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    Physical Characterization of an Unlensed, Dusty Star-forming Galaxy at z = 5.85
    (2019) Casey, Caitlin M.; Zavala, Jorge A.; Aravena, Manuel; Bethermin, M.; Caputi, Karina I.; Champagne, Jaclyn B.; Clements, David L.; Cunha, Elisabete da; Drew, Patrick; Treister, Ezequiel