Browsing by Subject "galaxies: high-redshift"

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    Overdensities of SMGs around WISE-selected, ultraluminous, high-redshift AGNs
    (2017) Jones, Suzy F; Blain, Andrew W; Assef, Roberto J; Eisenhardt, Peter; Lonsdale, Carol; Condon, James; Farrah, Duncan; Tsai, Chao-Wei; Bridge, Carrie; Wu, Jingwen; Wright, Edward L; Jarrett, Tom
    We investigate extremely luminous dusty galaxies in the environments around Wide-field Infrared Survey Explorer (WISE)-selected hot dust-obscured galaxies (Hot DOGs) and WISE/radio-selected active galactic nuclei (AGNs) at average redshifts of z = 2.7 and 1.7, respectively. Previous observations have detected overdensities of companion submillimetre-selected sources around 10 Hot DOGs and 30 WISE/radio AGNs, with overdensities of similar to 2-3 and similar to 5-6, respectively. We find that the space densities in both samples to be overdense compared to normal star-forming galaxies and submillimetre galaxies (SMGs) in the Submillimetre Common-User Bolometer Array 2 (SCUBA-2) Cosmology Legacy Survey (S2CLS). Both samples of companion sources have consistent mid-infrared (mid-IR) colours and mid-IR to submm ratios as SMGs. The brighter population around WISE/radio AGNs could be responsible for the higher overdensity reported. We also find that the star formation rate densities are higher than the field, but consistent with clusters of dusty galaxies. WISE-selected AGNs appear to be good signposts for protoclusters at high redshift on arcmin scales. The results reported here provide an upper limit to the strength of angular clustering using the two-point correlation function. Monte Carlo simulations show no angular correlation, which could indicate protoclusters on scales larger than the SCUBA-2 1.5-arcmin scale maps.
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    The Role of the Most Luminous Obscured AGNs in Galaxy Assembly at z similar to 2
    (2017) Farrah, Duncan; Petty, Sara; Blain, Andrew; Efstathiou, Andreas; Lacy, Mark; Stern, Daniel; Lake, Sean; Jarrett, Tom; Benford, Dominic; Tsai, Chao-Wei; Assef, Roberto; Moustakas, Leonidas
    We present Hubble Space Telescope WFC3 F160W imaging and infrared spectral energy distributions for 12 extremely luminous, obscured active galactic nuclei (AGNs) at 1.8 < z < 2.7. selected via "hot, dust-obscured" mid-infrared colors. Their infrared luminosities span (2-15) x 10(13) L-circle dot, making them among the most luminous objects in the universe at z similar to 2. In all cases, the infrared emission is consistent with arising at least for the. most part from AGN activity. The AGN fractional luminosities are higher than those in either submillimeter galaxies. or AGNs selected via other mid-infrared criteria. Adopting the G, M-20, and A morphological parameters, together with traditional classification boundaries, infers that three-quarters of the sample are mergers. Our sample does not, however, show any correlation between the considered morphological parameters and either infrared luminosity or AGN fractional luminosity. Moreover, the asymmetries and effective radii of our sample are distributed identically to those of massive galaxies at z similar to 2. We conclude that our sample is not preferentially associated with mergers, though a significant merger fraction is still plausible. Instead, we propose that our sample includes. examples of the massive galaxy population at z similar to 2 that harbor a briefly luminous, "flickering" AGN. and in which the G and M-20 values have been perturbed. due to either the AGN. and/or the earliest formation stages of a bulge in an inside-out manner. Furthermore, we find that the mass assembly of the central black holes in our sample leads the mass assembly of any bulge component. Finally, we speculate that our sample represents. a small fraction of the immediate antecedents of compact star-forming galaxies at z similar to 2.