Browsing by Author "Wu, J. W."

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    Hot Dust-obscured Galaxies with Excess Blue Light
    (2020) Assef, R. J.; Brightman, M.; Walton, D. J.; Stern, D.; Bauer, F. E.; Blain, A. W.; Diaz-Santos, T.; Eisenhardt, P. R. M.; Hickox, R. C.; Jun, H. D.; Psychogyios, A.; Tsai, C-W; Wu, J. W.
    Hot dust-obscured galaxies (Hot DOGs) are among the most luminous galaxies in the universe. Powered by highly obscured, possibly Compton-thick, active galactic nuclei (AGNs), Hot DOGs are characterized by spectral energy distributions that are very red in the mid-infrared yet dominated by the host galaxy stellar emission in the UV and optical. An earlier study identified a subsample of Hot DOGs with significantly enhanced UV emission. One target, W0204-0506, was studied in detail and, based on Chandra observations, it was concluded that the enhanced emission was most likely due to either extreme unobscured star formation (star formation rate > 1000Myr(-1)) or to light from the highly obscured AGN scattered by gas or dust into our line of sight. Here, we present a follow-up study of W0204-0506 as well as two more Hot DOGs with excess UV emission. For the two new objects we obtained Chandra/ACIS-S observations, and for all three targets we obtained Hubble Space Telescope/WFC3 F555W and F160W imaging. The analysis of these observations, combined with multiwavelength photometry and UV/optical spectroscopy suggests that UV emission is most likely dominated by light from the central highly obscured, hyperluminous AGN that has been scattered into our line of sight, by either gas or dust. We cannot decisively rule out, however, that star formation or a second AGN in the system may significantly contribute to the UV excess of these targets.
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    Imaging Polarization of the Blue-excess Hot Dust-obscured Galaxy WISE J011601.41-050504.0
    (2022) Assef, R. J.; Bauer, F. E.; Blain, A. W.; Brightman, M.; Diaz-Santos, T.; Eisenhardt, P. R. M.; Jun, H. D.; Stern, D.; Tsai, C-W; Walton, D. J.; Wu, J. W.
    We report on VLT/FORS2 imaging polarimetry observations in the R (Special) band of WISE J011601.41-050504.0 (W0116-0505), a heavily obscured hyperluminous quasar at z = 3.173 classified as a Hot Dust-obscured Galaxy (Hot DOG) based on its mid-IR colors. Recently, Assef et al. identified W0116-0505 as having excess rest-frame optical/UV emission and concluded that this excess emission is most likely scattered light from the heavily obscured AGN. We find that the broadband rest-frame UV flux is strongly linearly polarized (10.8% +/- 1.9%, with a polarization angle of 74 degrees +/- 9 degrees), confirming this conclusion. We analyze these observations in the context of a simple model based on scattering either by free electrons or by optically thin dust, assuming a classical dust torus with polar openings. Both can replicate the degree of polarization and the luminosity of the scattered component for a range of geometries and column densities, but we argue that optically thin dust in the ISM is the more likely scenario. We also explore the possibility that the scattering medium corresponds to an outflow recently identified for W0116-0505. This is a feasible option if the outflow component is biconical with most of the scattering occurring at the base of the receding outflow. In this scenario, the quasar would still be obscured even if viewed face-on but might appear as a reddened type 1 quasar once the outflow has expanded. We discuss a possible connection between blue-excess Hot DOGs, extremely red quasars, reddened type 1 quasars, and unreddened quasars that depends on a combination of evolution and viewing geometry.
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    Spectral Classification and Ionized Gas Outflows in z ∼ 2 WISE-selected Hot Dust-obscured Galaxies
    (2020) Jun, H. D.; Assef, R. J.; Bauer, Franz Erik; Blain, A.; Díaz Santos, T.; Eisenhardt, P. R. M.; Stern, D.; Tsai, C. W.; Wright, E. L.; Wu, J. W.