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Articles 1 - 7 of 7
Full-Text Articles in Physical Sciences and Mathematics
The Halo Occupation Distribution Of X-Ray-Bright Active Galactic Nuclei: A Comparison With Luminous Quasars, Jonathan Richardson, Suchetana Chatterjee, Zheng Zheng, Adam D. Myers, Ryan Hickox
The Halo Occupation Distribution Of X-Ray-Bright Active Galactic Nuclei: A Comparison With Luminous Quasars, Jonathan Richardson, Suchetana Chatterjee, Zheng Zheng, Adam D. Myers, Ryan Hickox
Dartmouth Scholarship
We perform halo occupation distribution (HOD) modeling of the projected two-point correlation function (2PCF) of high-redshift (z~1.2) X-ray-bright active galactic nuclei (AGN) in the XMM-COSMOS field measured by Allevato et al. The HOD parameterization is based on low-luminosity AGN in cosmological simulations. At the median redshift of z~1.2, we derive a median mass of (1.02+0.21/-0.23)x10^{13} Msun/h for halos hosting central AGN and an upper limit of ~10% on the AGN satellite fraction. Our modeling results indicate (at the 2.5-sigma level) that X-ray AGN reside in more massive halos compared to more bolometrically luminous, optically-selected quasars at similar redshift. The modeling …
Spectral Energy Distributions Of Type 1 Agn In Xmm-Cosmos – Ii. Shape Evolution, Heng Hao, Martin Elvis, Francesca Civano, Gianni Zamorani
Spectral Energy Distributions Of Type 1 Agn In Xmm-Cosmos – Ii. Shape Evolution, Heng Hao, Martin Elvis, Francesca Civano, Gianni Zamorani
Dartmouth Scholarship
The mid-infrared to ultraviolet (0.1 -- 10 μm) spectral energy distribution (SED) shapes of 407 X-ray-selected radio-quiet type 1 AGN in the wide-field ``Cosmic Evolution Survey" (COSMOS) have been studied for signs of evolution. For a sub-sample of 200 radio-quiet quasars with black hole mass estimates and host galaxy corrections, we studied their mean SEDs as a function of a broad range of redshift, bolometric luminosity, black hole mass and Eddington ratio, and compared them with the Elvis et al. (1994, E94) type 1 AGN mean SED. We found that the mean SEDs in each bin are closely similar to …
Finding Rare Agn: Xmm-Newton And Chandra Observations Of Sdss Stripe 82, Stephanie M. Lamassa, C. Megan Urry, Nico Cappelluti, Francesca Civano
Finding Rare Agn: Xmm-Newton And Chandra Observations Of Sdss Stripe 82, Stephanie M. Lamassa, C. Megan Urry, Nico Cappelluti, Francesca Civano
Dartmouth Scholarship
We have analysed the XMM–Newton and Chandra data overlapping ∼16.5 deg2 of Sloan Digital Sky Survey Stripe 82, including ∼4.6 deg2 of proprietary XMM–Newton data that we present here. In total, 3362 unique X-ray sources are detected at high significance. We derive the XMM–Newton number counts and compare them with our previously reported Chandra logN–logS relations and other X-ray surveys. The Stripe 82 X-ray source lists have been matched to multiwavelength catalogues using a maximum likelihood estimator algorithm. We discovered the highest redshift (z = 5.86) quasar yet identified in an X-ray survey. We …
Salt Long-Slit Spectroscopy Of Luminous Obscured Quasars: An Upper Limit On The Size Of The Narrow-Line Region?, Kevin N. Hainline, Ryan Hickox, Jenny E. Greene, Adam D. Myers, Nadia L. Zakamska
Salt Long-Slit Spectroscopy Of Luminous Obscured Quasars: An Upper Limit On The Size Of The Narrow-Line Region?, Kevin N. Hainline, Ryan Hickox, Jenny E. Greene, Adam D. Myers, Nadia L. Zakamska
Dartmouth Scholarship
We present spatially resolved long-slit spectroscopy from the Southern African Large Telescope (SALT) to examine the spatial extent of the narrow-line regions (NLRs) of a sample of 8 luminous obscured quasars at 0.10 < z < 0.43. Our results are consistent with an observed shallow slope in the relationship between NLR size and L_[OIII], which has been interpreted to indicate that NLR size is limited by the density and ionization state of the NLR gas rather than the availability of ionizing photons. We also explore how the NLR size scales with a more direct measure of instantaneous AGN power using mid-IR photometry from WISE, which probes warm to hot dust near the central black hole and so, unlike [OIII], does not depend on the properties of the NLR. Using our results as well as samples from the literature, we obtain a power-law relationship between NLR size and L_8micron that is significantly steeper than that observed for NLR size and L_[OIII]. We find that the size of the NLR goes approximately as L^(1/2)_8micron, as expected from the simple scenario of constant-density clouds illuminated by a central ionizing source. We further see tentative evidence for a flattening of the relationship between NLR size and L_8micron at the high luminosity end, and propose that we are seeing a limiting NLR size of 10 - 20 kpc, beyond which the availability of gas to ionize becomes too low. We find that L_[OIII] ~ L_8micron^(1.4), consistent with a picture in which the L_[OIII] is dependent on the volume of the NLR. These results indicate that high-luminosity quasars have a strong effect in ionizing the available gas in a galaxy.
A Quasar–Galaxy Mixing Diagram: Quasar Spectral Energy Distribution Shapes In The Optical To Near-Infrared, Heng Hao, Martin Elvis, Angela Bongiorno, Gianni Zamorani, Andrea Merloni, C. Kelly, Francesca Civano
A Quasar–Galaxy Mixing Diagram: Quasar Spectral Energy Distribution Shapes In The Optical To Near-Infrared, Heng Hao, Martin Elvis, Angela Bongiorno, Gianni Zamorani, Andrea Merloni, C. Kelly, Francesca Civano
Dartmouth Scholarship
We define a quasar–galaxy mixing diagram using the slopes of their spectral energy distributions (SEDs) from 1 μm to 3000 Å and from 1 to 3 μm in the rest frame. The mixing diagram can easily distinguish among quasar-dominated, galaxy-dominated and reddening-dominated SED shapes. By studying the position of the 413 XMM-selected type 1 AGN in the wide-field ‘Cosmic Evolution Survey’ in the mixing diagram, we find that a combination of the Elvis et al. mean quasar SED with various contributions from galaxy emission and some dust reddening is remarkably effective in describing the SED shape from 0.3 to …
Finding Rare Agn: X-Ray Number Counts Of Chandra Sources In Stripe 82, Stephanie M. Lamassa, C. Megan Urry, Eilat Glikman, Nico Cappelluti, Francesca Civano
Finding Rare Agn: X-Ray Number Counts Of Chandra Sources In Stripe 82, Stephanie M. Lamassa, C. Megan Urry, Eilat Glikman, Nico Cappelluti, Francesca Civano
Dartmouth Scholarship
We present the first results of a wide area X-ray survey within the Sloan Digital Sky Survey (SDSS) Stripe 82, a 300 deg2 region of the sky with a substantial investment in multi-wavelength coverage. We analyzed archival {\it Chandra} observations that cover 7.5 deg2 within Stripe 82 ("Stripe 82 ACX"), reaching 4.5σ flux limits of 7.9×10−16, 3.4×10−15 and 1.8×10−15 erg s−1 cm−2 in the soft (0.5-2 keV), hard (2-7 keV) and full (0.5-7 keV) bands, to find 774, 239 and 1118 X-ray sources, respectively. Three hundred twenty-one sources are detected only in the full band and 9 sources are detected …
Narrow-Line Region Gas Kinematics Of 24 264 Optically Selected Agn: The Radio Connection, J. R. Mullaney, D. M. Alexander, S. Fine, A. D. Goulding, C. M. Harrison, R. C. Hickox
Narrow-Line Region Gas Kinematics Of 24 264 Optically Selected Agn: The Radio Connection, J. R. Mullaney, D. M. Alexander, S. Fine, A. D. Goulding, C. M. Harrison, R. C. Hickox
Dartmouth Scholarship
Using a sample of 24 264 optically selected active galactic nuclei (AGNs) from the SDSS DR7 data base, we characterize how the profile of the [O iii] λ5007 emission line relates to bolometric luminosity (LAGN), Eddington ratio, radio loudness, radio luminosity (L1.4 GHz) and optical class (i.e. broad/narrow-line Seyfert 1, type 2) to determine what drives the kinematics of this kpc-scale line emitting gas. First, we use spectral stacking to characterize how the average [O iii] λ5007 profile changes as a function of these five variables. After accounting for the known correlation between L …