Showing papers by "Carol J. Lonsdale published in 2015"

The most luminous galaxies discovered by wise

Abstract: We present 20 Wide-field Infrared Survey Explorer (WISE)-selected galaxies with bolometric luminosities L_(bol) > 10^(14) L☉, including five with infrared luminosities L_(IR) ≡ L_((rest 8–1000 μm)) > 10^(14) L☉. These "extremely luminous infrared galaxies," or ELIRGs, were discovered using the "W1W2-dropout" selection criteria which requires marginal or non-detections at 3.4 and 4.6 μm (W1 and W2, respectively) but strong detections at 12 and 22 μm in the WISE survey. Their spectral energy distributions are dominated by emission at rest-frame 4–10 μm, suggesting that hot dust with T_d ~ 450 K is responsible for the high luminosities. These galaxies are likely powered by highly obscured active galactic nuclei (AGNs), and there is no evidence suggesting these systems are beamed or lensed. We compare this WISE-selected sample with 116 optically selected quasars that reach the same L_(bol) level, corresponding to the most luminous unobscured quasars in the literature. We find that the rest-frame 5.8 and 7.8 μm luminosities of the WISE-selected ELIRGs can be 30%–80% higher than that of the unobscured quasars. The existence of AGNs with L_(bol) > 10^(14) L☉ at z > 3 suggests that these supermassive black holes are born with large mass, or have very rapid mass assembly. For black hole seed masses ~10^3 M☉, either sustained super-Eddington accretion is needed, or the radiative efficiency must be <15%, implying a black hole with slow spin, possibly due to chaotic accretion.

ALMA detection of a disc-dominated [C ii] emission line at z=4.6 in the luminous QSO J1554+1937

Abstract: We present observations and analysis of an unusual [C II] emission line in the very luminous QSO SDSS J155426.16+193703.0 at z~4.6. The line is extremely broad (FWHM 735 km/s) and seems to have a flat-topped or double-peaked line profile. A velocity map of the line shows a gradient across the source that indicates large-scale rotation of star-forming gas. Together, the velocity map and line profile suggest the presence of a massive rotating disc with a dynamical mass M_dyn > 5x10^10 M_sun. Using the assumption of a rotating disc origin, we employ an empirical relation between galaxy disc circular velocity and bulge velocity dispersion (sigma) to estimate that sigma > 310 km/s, subject to a correction for the unknown disc inclination. This result implies that this source is consistent with the local M--sigma relation, or offset at most by an order of magnitude in black hole mass. In contrast, the assumption of a bulge origin for the [C II] emission line would lead to a conclusion that the black hole is nearly two orders of magnitude more massive than predicted by the M--sigma relation, similar to previous findings for other high-redshift QSOs. As disc rotation may be a common origin for [C II] emission at high redshifts, these results stress that careful consideration of dynamical origins is required when using observations of this line to derive properties of high-redshift galaxies.

Radio Jet Feedback and Star Formation in Heavily Obscured Quasars at Redshifts ~0.3-3, I: ALMA Observations

Abstract: We present ALMA 870 micron (345 GHz) data for 49 high redshift (0.47

ALMA detection of a disc-dominated [C II] emission line at z=4.6 in the luminous QSO J1554+1937

Abstract: We present observations and analysis of an unusual [C II] emission line in the very luminous QSO SDSS J155426.16+193703.0 at z~4.6. The line is extremely broad (FWHM 735 km/s) and seems to have a flat-topped or double-peaked line profile. A velocity map of the line shows a gradient across the source that indicates large-scale rotation of star-forming gas. Together, the velocity map and line profile suggest the presence of a massive rotating disc with a dynamical mass M_dyn > 5x10^10 M_sun. Using the assumption of a rotating disc origin, we employ an empirical relation between galaxy disc circular velocity and bulge velocity dispersion (sigma) to estimate that sigma > 310 km/s, subject to a correction for the unknown disc inclination. This result implies that this source is consistent with the local M--sigma relation, or offset at most by an order of magnitude in black hole mass. In contrast, the assumption of a bulge origin for the [C II] emission line would lead to a conclusion that the black hole is nearly two orders of magnitude more massive than predicted by the M--sigma relation, similar to previous findings for other high-redshift QSOs. As disc rotation may be a common origin for [C II] emission at high redshifts, these results stress that careful consideration of dynamical origins is required when using observations of this line to derive properties of high-redshift galaxies.

ALMA detected overdensity of sub-mm sources around WISE/NVSS-selected z~2 dusty quasars

Abstract: We study the environments of 49 WISE/NVSS-selected dusty, hyper-luminous, z~2 quasars using the Atacama Large Millimeter/Sub-millimeter Array (ALMA) 345GHz images. We find that 17 of the 49 WISE/NVSS sources show additional sub-mm galaxies within the ALMA primary beam, probing scales within ~150 kpc. We find a total of 23 additional sub-mm sources, four of which in the field of a single WISE/NVSS source. The measured 870 um source counts are ~10 times expectations for unbiased regions, suggesting such hyper-luminous dusty quasars are excellent at probing high-density peaks.