Hubble Space Telescope Imaging of Bright Lyman-break Galaxy Candidates from the Sloan Digital Sky Survey: Not LBGs After All

We present deep Hubble Space Telescope ACS and NICMOS images of six bright Lyman-break galaxy candidates that were previously discovered in the Sloan Digital Sky Survey. We find that five of the objects are consistent with unresolved point sources. Although somewhat atypical of the class, they are most likely LoBAL quasars, perhaps FeLoBALs. The sixth object, J1147, has a faint companion galaxy located ~0.8 arcsec to the southwest. The companion contributes ~8% of the flux in the observed-frame optical and infrared. It is unknown whether this companion is located at the same redshift as J1147.Comment: 16 pages, 8 figures, 3 tables; accepted for publication in A

Constraints on the broad line region from regularized linear inversion: Velocity-delay maps for five nearby active galactic nuclei

Reverberation mapping probes the structure of the broad emission-line region (BLR) in active galactic nuclei (AGN). The kinematics of the BLR gas can be used to measure the mass of the central supermassive black hole. The main uncertainty affecting black hole mass determinations is the structure of the BLR. We present a new method for reverberation mapping based on regularized linear inversion (RLI) that includes modelling of the AGN continuum light curves. This enables fast calculation of velocity-resolved response maps to constrain BLR structure. RLI allows for negative response, such as when some areas of the BLR respond in inverse proportion to a change in ionizing continuum luminosity. We present time delays, integrated response functions, and velocity-delay maps for the $\rm{H}\,\beta$ broad emission line in five nearby AGN, as well as for $\rm{H}\,\alpha$ and $\rm{H}\,\gamma$ in Arp 151, using data from the Lick AGN Monitoring Project 2008. We find indications of prompt response in three of the objects (Arp 151, NGC 5548 and SBS 1116+583A) with additional prompt response in the red wing of $\rm{H}\,\beta$. In SBS 1116+583A we find evidence for a multimodal broad prompt response followed by a second narrow response at 10 days. We find no clear indications of negative response. The results are complementary to, and consistent with, other methods such as cross correlation, maximum entropy and dynamical modelling. Regularized linear inversion with continuum light curve modelling provides a fast, complementary method for velocity-resolved reverberation mapping and is suitable for use on large datasets.Comment: 20 pages, 13 figures, accepted to MNRA

Light echoes

The first light echo - scattered light from a stellar outburst arriving at the Earth months or years after the direct light from the event - was detected more than 100 years ago, around Nova Persei 1901. Renewed interest in light echoes has come from the spectacular echo around V838 Monocerotis, and from discoveries of light echoes from historical and prehistorical supernovæ in the Milky Way and Large Magellanic Cloud as well as from the 19 th-century Great Eruption of η Carinae. A related technique is reverberation mapping of active galactic nuclei. This report of a workshop on Light Echoes gives an introduction to light echoes, and summarizes presentations on discoveries of light echoes from historical and prehistorical events, light and shadow echoes around R CrB stars, and reverberation mapping. © 2012 International Astronomical Union

Reverberation Mapping of IC4329A

We present the results of a new reverberation mapping campaign for the broad-lined active galactic nucleus (AGN) in the edge-on spiral IC4329A. Monitoring of the optical continuum with $V-$band photometry and broad emission-line flux variability with moderate-resolution spectroscopy allowed emission-line light curves to be measured for H$\beta$, H$\gamma$, and HeII $\lambda 4686$. We find a time delay of $16.3^{+2.6}_{-2.3}$ days for H$\beta$, a similar time delay of $16.0^{+4.8}_{-2.6}$ days for H$\gamma$, and an unresolved time delay of $-0.6^{+3.9}_{-3.9}$ days for HeII. The time delay for H$\beta$ is consistent with the predicted value from the relationship between AGN luminosity and broad line region radius, after correction for the $\sim2.4$mag of intrinsic extinction at 5100A. Combining the measured time delay for H$\beta$ with the broad emission line width and an adopted value of $\langle f \rangle = 4.8$, we find a central supermassive black hole mass of $M_{\rm BH}=6.8^{+1.2}_{-1.1}\times10^7 M_{\rm \odot}$. Velocity-resolved time delays were measured across the broad H$\beta$ emission-line profile and may be consistent with an ''M''-like shape. Modeling of the full reverberation response of H$\beta$ was able to provide only modest constraints on some parameters, but does exhibit agreement with the black hole mass and average time delay. The models also suggest that the AGN structure is misaligned by a large amount from the edge-on galaxy disk. This is consistent with expectations from the unified model of AGNs, in which broad emission lines are expected to be visible only for AGNs that are viewed at relatively face-on inclinations.Comment: 12 pages, 6 figures, 3 tables; accepted for publication in Ap