Had I special: The Astronomical Contributions of the Herschel Family

НазваниеHad I special: The Astronomical Contributions of the Herschel Family
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Testing the Radiative-Driving Hypothesis of Quasar Outflows

Michele A. Stark1, R. Ganguly1, S. C. Gallagher2, R. Gibson3, M. S. Brotherton4
1University of Michigan - Flint, 2University of Western Ontario, Canada, 3University of Washington, 4University of Wyoming.

Exhibit Hall

Outflows are seen prominently in the UV spectra of Broad Absorption Line (BAL) QSOs. Models of radiatively-driven outflows predict that the velocity should scale with UV luminosity. Observations show that the UV luminosity only provides a cap to the velocity. One explanation is that the X-ray absorbing gas in an individual quasar provides a shield that improves its radiative-driving efficiency. That is, quasars with thick shields can accelerate gas to higher velocity. X-ray observations of BALQSOs support this in the sense that BALQSOs with more soft X-ray absorption tend to have higher velocity outflows. But there is much scatter in this trend, making the underlying physics difficult to extract. To combat this, we conducted an experiment using exploratory Chandra-ACIS observations of 12 carefully-selected z=1.7-2.0 BALQSOs. These BALQSOs were chosen to have very narrow ranges in (1) UV luminosity, (2) UV spectral shape, and (3) absorption velocity width. Within this otherwise uniform sample, the outflow velocities range from 4500km/s to 18000km/s, a factor of four. All objects are detected in the full band (0.5-8keV), with count rates in the range (0.5-5)e-3 cps, and have hardness ratios in the range -0.6 to 0.3. We compare the X-ray brightnesses and spectral shapes of our sample with those of more diverse samples of BALQSOs.
We gratefully acknowledge support through Chandra grant GO9-0120X.


Toward a Prescription for Feedback from Quasar Outflows

Rajib Ganguly1, M. Bourjaily1, J. Munsell1, M. S. Brotherton2, A. Bhattacharjee2, J. Runnoe2, J. C. Charlton3, M. Eracleous3
1Univ. of Michigan-Flint, 2Univ. of Wyoming, 3The Pennsylvania State University.

Exhibit Hall

Models have shown that quasars are a crucial ingredient in the evolution of massive galaxies. Outflows play a key role in the story of quasars and their host galaxies, by helping regulate the accretion process, the star-formation rate and mass of the host galaxy (i.e., feedback). The prescription for modeling outflows as a contributor to feedback requires knowledge of the outflow velocity, distance, geometry, and column density. In particular, we need to understand how these depend on physical parameters and how much is determined stochastically (and with what distribution). For this purpose, we are examining a sample of 14000 z=1.7-2.0 quasars from the Sloan Digital Sky Survey. This redshift range permits the following from the SDSS spectra: (1) separation of objects that do and do not exhibit outflows; (2) classification/measurement of outflow properties (ionization, velocity, velocity width); and (3) estimates of the quasar black hole mass. To this, we are adding photometry from GALEX, 2MASS, and ROSAT in an effort to characterize more fully the quasar SEDs. ROSAT photometry provides estimates of the level of soft X-ray absorption, which helps regulate the velocity of outflows. GALEX photometry samples the extreme ultraviolet range where several high ionization species, that may be present in the outflows, absorb light. 2MASS photometry samples the rest-frame optical, where the effects of absorption and dust reddening are minimal, yield better estimates of the bolometric luminosity (hence, Eddington ratio). In this poster, we will present preliminary measurements of the amount of absorption in the soft X-ray and extreme ultraviolet bands as a function of both outflow properties and quasar physical properties.
This material is based upon work supported by the National Aeronautics and Space Administration under Grant No. 09-ADP09-0016 issued through the Astrophysics Data Analysis Program.


Recent Star-formation in Post-Starburst Quasars

Shonda Townsend1, R. Ganguly1, A. Strom2, S. Cales3, M. S. Brotherton3
1University of Michigan - Flint, 2University of Arizona, 3University of Wyoming.

Exhibit Hall

Post-Starburst Quasars (PSQ, alternatively Q+As) show simultaneously the spectrum of a massive A-type stellar population and a quasar. The prototype PSQ, UNJ1025-0040, shows a UV excess over the quasar spectrum, indicating more recent star-formation (Brotherton et al 2002). To gauge the frequency and distribution of these younger stellar populations in PSQs, we have collected GALEX (GR45) and 2MASS photometry for 409 objects. The objects are catalog 609 spectroscopically-selected PSQs from Brotherton et al. (2010) that uses similar criteria as Zabludoff et al. (1996) for post-starburst galaxies (PSG, E+A). For comparison, we have compiled two samples: (1) 16,000 quasars that is matched in redshift (0.01-0.7) and Sloan-u magnitude (16.1-21.2), which is blueward of the Balmer edge and provides the least contamination from the massive stellar population; and (2) 500 PSGs from Goto et al. (2007). 389 (55) PSQs show an NUV (FUV) excess over the expected UV flux if the underlying quasar were ``normal.’’ 126 (460) objects show an NUV (FUV) decrement. The observed NUV to u-band flux ratio of the median PSQ rises from ~1 at z=0.01 to 2.5 at z=0.4, while the same for the median QSO remains at ~1. The observed FUV to u-band flux ratio of the median QSO rises slightly from ~0.6 to ~0.8 over the redshift range 0.05-0.2, whereas the median PSQ is nearly a factor of three lower. The disparity between the median PSQ and QSO suggests the presence of young stars that add in NUV light, but not FUV light. To quantify the youth and mass of this putative population, we will present preliminary efforts to model PSQs using two simple stellar populations, an underlying quasar, and dust reddening. We acknowledge funding from GALEX through grant NNX10AC63G.


Parsec-Scale Localization of the Quasar SDSS J1536+0441A, a Candidate Binary Black Hole System

J. M. Wrobel1, A. Laor2
1NRAO, 2Technion, Israel.

Exhibit Hall

The radio-quiet quasar (RQQ) SDSS J1536+0441A shows two broad-line emission systems, recently interpreted as a binary black hole (BBH) system with a subparsec separation; as a double-peaked emitter (DPE); or as both types of systems. The NRAO VLBA was used to search for 8.4 GHz emission from SDSS J1536+0441A, focusing on the localization region for the broad-line emission, of area 5400 mas2 (0.15 kpc2). One source was detected, with a diameter of less than 1.63 mas (8.5 pc) and a brightness temperature Tb > 1.2 x 107 K. New NRAO VLA photometry at 22.5 GHz, and earlier photometry at 8.5 GHz, gives a rising spectral slope of alpha = 0.35+/-0.08. The slope implies an optically thick synchrotron source, with a radius of about 0.04 pc, and thus Tb ~ 4.8 x 1010 K. The implied radio sphere at the rest frequency 31.2 GHz has a radius of 800 gravitational radii, just below the size of the broad line region in this object. Observations at higher frequencies with the EVLA and ALMA can probe whether or not the radio sphere is as compact as expected from the coronal framework for the radio emission of RQQs. The NRAO is a facility of the NSF operated under cooperative agreement by AUI.


Galaxy-scale Clouds Of Ionized Gas Around Agn - History And Obscuration

Drew Chojnowski1, W. C. Keel2
1Texas Christian University, 2University of Alabama.

Exhibit Hall

Motivated by the discovery of Hanny's Voorwerp, a 45-kpc highly-ionized cloud near the spiral galaxy IC 2497, and accompanying evidence for strong variability of its AGN over 105 year scales, members of the Galaxy Zoo project have carried out surveys for similar (albeit smaller) ionized clouds around galaxies both with and without spectroscopic AGN. The color-composite SDSS images detect strong [OIII] in the g band at low z, allowing a useful color search of Galaxy Zoo targets. In addition, a targeted search was made of over 16,000 spectroscopic AGN and candidates. We used SDSS data to produce crude [OIII] images of the top candidates, and obtained long-slit optical spectra from KPNO and Lick for 30 of the most promising. Roughly half of the spectra showed extended [OIII]λ5007 emission, some exceeding 30 kpc in radial extent. Of the 16 extended clouds we identified, 11 lie in strongly interacting or merging systems, probably because these events leave cold gas out of the plane to be ionized. Most nuclei of extended cloud hosts are type 2 Seyferts. We consider the energy budgets, between ionizing luminosity required for the most distant line emission and the FIR output of the nucleus, to see whether any suggest strong variability rather than obscuration. Several galaxies have such strong mismatches that obscuration alone becomes implausible as an explanation for the strong ionizing continuum, and are candidates for fading events similar to that in IC 2497 and Hanny's Voorwerp. This project was funded by the National Science Foundation Research Experiences for Undergraduates (REU) program through grant NSF AST-1004872.


The History And Environment Of A Faded Quasar: HST Observations Of Hanny's Voorwerp And IC 2497

William C. Keel1, C. Lintott2, K. Schawinski3, V. Bennert4, D. Thomas5, A. Manning1, S. D. Chojnowski6, H. van Arkel7, S. Lynn8, Galaxy Zoo team
1Univ. of Alabama, 2Adler Planetarium, 3Yale Univ., 4UCSB, 5Univ. of Portsmouth, United Kingdom, 6Texas Christian Univ., 7CITAVERDE College, Netherlands, 8Oxford Univ., United Kingdom.

Exhibit Hall

Perhaps the signature discovery of the Galaxy Zoo citizen-science project has been Hanny's Voorwerp, high-ionization cloud extending 45 kpc from the spiral galaxy IC 2497. It must be ionized by a luminous AGN, either deeply obscured or having dimmed dramatically within 200,000 years. We explore this system using HST imaging and spectroscopy. The disk of IC 2497 is warped, with complex dust absorption near the nucleus; the near-IR peak coincides closely with the VLBI core marking the AGN. STIS spectra show the AGN as a low-luminosity LINER, with ionization parameter log U= -3.5, matching its weak X-ray emission. The nucleus is accompanied by an expanding loop of ionized gas ∼ 500 pc in diameter, opposite Hanny's Voorwerp. The loop's Doppler span 300 km/s implies kinematic age < 700,000 years. We find no high-ionization gas near the core, further evidence that the AGN is seen at a low radiative output (perhaps now dominated by kinetic energy). [O III] and Hα +[N II] ACS images show fine structure in Hanny's Voorwerp, including limb-brightened sections suggesting modest interaction with a galactic outflow. We identify small regions ionized by recent star formation, unlike the AGN ionization of the overall cloud. These H II regions contain blue continuum objects, consistent with young stellar populations; these occur where projected closest to IC 2497, perhaps meaning that the star formation was triggered by compression from an outflow. The ionization-sensitive [O III]/Hα ratio shows broad bands across the object, and no discernible pattern with emission-line structures or near the prominent "hole" in the ionized gas. These results fit with our picture of an ionization echo from an AGN whose ionizing luminosity has dropped by a factor >100 within the last 200,000 years. Such rapid fluctuations in luminosity could alter our understanding of AGN demographics. Supported by NASA/STScI.


Twenty-Year Optical Variability of The Blazar PKS 1749+096: Exponential Outbursts?

Thomas J. Balonek1, M. T. Lam1, P. A. Patrick1, E. L. Scott1, A. J. Kaercher1, J. Rupert2, T. Taber2, P. Hegel3, Y. H. N. Tam4, A. Morin5, K. Levandowski6, E. L. Graber7, T. S. Quirk8
1Colgate Univ., 2Vassar Coll., 3Wesleyan Univ., 4Williams Coll., 5RPI, 6Wellesley Coll., 7Univ. Michigan, 8Siena Coll..

Exhibit Hall

We present the twenty-year R-band optical variability light curve for the BL Lac type quasar PKS 1749+096. We investigate the characteristic timescales and intensity of outbursts and flares by fitting exponential profiles to the variations. PKS 1749+096 underwent strong optical outbursts during the summers of 2007 and 2008, reaching its brightest optical level in two decades, and exhibited an inactive period during summer 2009. We compare these two outbursts with lower amplitude well-sampled variations in 2000 through 2003. Observations were obtained as part of the intensive blazar variability monitoring program at the Colgate University Foggy Bottom Observatory (FBO). We gratefully acknowledge support for student research through an REU grant to the Keck Northeast Astronomy Consortium from the National Science Foundation, the NASA / New York Space Grant, and the Justus and Jayne Schlichting Student Research Fund at Colgate University.


Time Series Analysis of the Quasar PKS 1749+096

Michael T. Lam1, T. J. Balonek1
1Colgate University.

Exhibit Hall

Multiple timescales of variability are observed in quasars at a variety of wavelengths, the nature of which is not fully understood. In 2007 and 2008, the quasar 1749+096 underwent two unprecedented optical outbursts, reaching a brightness never before seen in our twenty years of monitoring. Much lower level activity had been seen prior to these two outbursts. We present an analysis of the timescales of variability over the two regimes using a variety of statistical techniques. An IDL software package developed at Colgate University over the summer of 2010, the Quasar User Interface (QUI), provides effective computation of four time series functions for analyzing underlying trends present in generic, discretely sampled data sets. Using the Autocorrelation Function, Structure Function, and Power Spectrum, we are able to quickly identify possible variability timescales. QUI is also capable of computing the Cross-Correlation Function for comparing variability at different wavelengths. We apply these algorithms to 1749+096 and present our analysis of the timescales for this object. Funding for this project was received from Colgate University, the Justus and Jayne Schlichting Student Research Fund, and the NASA / New York Space Grant.


Feedback from radio-quiet quasars

Nadia L. Zakamska1, J. E. Greene2
1KIPAC/Stanford, 2UT Austin.

Exhibit Hall

The correlations between properties of supermassive black holes and stellar spheroids in nearby galaxies strongly suggest that there is a physical connection between these two components, even though their masses and physical scales are vastly different. There is growing evidence that radio-loud active galactic nuclei exert a strong feedback on the gas in their host galaxies, providing a possible mechanism for such connection. However, as only a minority of active galaxies are radio-loud at any given time, the radio-loud feedback may only be a part of the explanation. Here we report the discovery of powerful outflows from radio-quiet quasars observed in the emission lines of the photo-ionized gas.

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