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Papers by Rosalie McGurk
We present optical spectroscopy of six short-period cataclysmic variable stars obtained with ESO&... more We present optical spectroscopy of six short-period cataclysmic variable stars obtained with ESO's 8-meter Very Large Telescope. Four of the stars and their K1 amplitudes are GW Lib, 43.3 km/s; BW Scl, 56.6 km/s; V436 Cen, 77.5 km/s; VY Aqr, 48.7 km/s; and Z Cha, 180.6 km/s. We determined the mass ratio, q, for each system, but found likely unrealistic q values for GW Lib and Z Cha. GW Lib is a low inclination system and its accretion may be more of an accretion ring than an accretion disk. Z Cha's high inclination and strong hot spot impact the determination of q. V436 Cen's spectra show a strongly- rising blue continuum and Balmer decrements HAlpha/HBeta and HDelta/HBeta indicative an optically thick disk with a hot, thin chromosphere. WZ Sge was observed soon after its 2001 superoutburst. The emission lines were strongly dominated by the S-wave component leading to a unique radial velocity curve. We can model the RV variations as a combination of the underlying, weak ...
We apply Principal Component Analysis (PCA) to ~100,000 stellar spectra obtained by the Sloan Dig... more We apply Principal Component Analysis (PCA) to ~100,000 stellar spectra obtained by the Sloan Digital Sky Survey (SDSS). In order to avoid strong non-linear variation of spectra with effective temperature, the sample is binned into 0.02 mag wide intervals of the g-r color (-0.20<g-r<0.90, roughly corresponding to MK spectral types A3 to K3), and PCA is applied independently for each bin. In each color bin, the first four eigenspectra are sufficient to describe the observed spectra within the measurement noise. We discuss correlations of eigencoefficients with metallicity and gravity estimated by the Sloan Extension for Galactic Understanding and Exploration (SEGUE) Stellar Parameters Pipeline. The resulting high signal-to-noise mean spectra and the other three eigenspectra are made publicly available. These data can be used to generate high quality spectra for an arbitrary combination of effective temperature, metallicity, and gravity within the parameter space probed by the SDSS. The SDSS stellar spectroscopic database and the PCA results presented here offer a convenient method to classify new spectra, to search for unusual spectra, to train various spectral classification methods, and to synthesize accurate colors in arbitrary optical bandpasses.
The Astrophysical Journal, Sep 1, 2011
Active galaxies hosting two accreting and merging supermassive black holes (SMBHs)---dual active ... more Active galaxies hosting two accreting and merging supermassive black holes (SMBHs)---dual active galactic nuclei (AGNs)---are predicted by many current and popular models of black-hole-galaxy co-evolution. We present here the results of a program that has identified a set of probable dual AGN candidates based on near-infrared laser guide star adaptive optics imaging with the Keck II telescope. These candidates are selected from a complete sample of radio-quiet quasi-stellar objects (QSOs) drawn from the Sloan Digital Sky Survey (SDSS), which show double-peaked narrow AGN emission lines. Of the 12 AGNs imaged, we find 6 with double galaxy structure, of which four are in galaxy mergers. We measure the ionization of the two velocity components in the narrow AGN lines to test the hypothesis that both velocity components come from an active nucleus. The combination of a well-defined parent sample and high-quality imaging allows us to place constraints on the fraction of SDSS QSOs that host dual accreting black holes separated on kiloparsec scales: ~0.3%-0.65%. We derive from this fraction the time spent in a QSO phase during a typical merger and find a value that is much lower than estimates that arise from QSO space densities and galaxy merger statistics. We discuss possible reasons for this difference. Finally, we compare the SMBH mass distributions of single and dual AGNs and find little difference between the two within the limited statistics of our program, hinting that most SMBH growth happens in the later stages of a merger process.
The Astronomical Journal
We apply Principal Component Analysis (PCA) to ~100,000 stellar spectra obtained by the Sloan Dig... more We apply Principal Component Analysis (PCA) to ~100,000 stellar spectra obtained by the Sloan Digital Sky Survey (SDSS). In order to avoid strong nonlinear variation of spectra with effective temperature, the sample is binned into 0.02 mag wide intervals of the g – r color (–0.20 < g – r < 0.90, roughly corresponding to MK spectral types A3-K3), and PCA is applied independently for each bin. In each color bin, the first four eigenspectra are sufficient to describe the observed spectra within the measurement noise. We discuss correlations of eigencoefficients with metallicity and gravity estimated by the Sloan Extension for Galactic Understanding and Exploration Stellar Parameters Pipeline. The resulting high signal-to-noise mean spectra and the other three eigenspectra are made publicly available. These data can be used to generate high-quality spectra for an arbitrary combination of effective temperature, metallicity, and gravity within the parameter space probed by the SDSS....
Astronomical Journal, 2009
We present new K-band spectra of VY Aqr and EI Psc obtained with NIRSPEC on the Keck II telescope... more We present new K-band spectra of VY Aqr and EI Psc obtained with NIRSPEC on the Keck II telescope. We find a best-fitting spectral type of K4 for EI Psc, in agreement with the previous classification. The Keck spectrum of VY Aqr suggests an M0 spectral type, much hotter than previously derived. We re-reduce the original data for VY Aqr
Hierarchical merging of smaller structures into larger ones is fundamental to galaxy evolution in... more Hierarchical merging of smaller structures into larger ones is fundamental to galaxy evolution in LambdaCDM cosmologies. The Mbh sigma relation suggests that when galaxies merge, their central supermassive black holes merge and grow as well. Using spectroscopic surveys such as SDSS and DEEP, candidates for galaxies containing two active black holes or an offset black hole have been identified by
Proceedings of the International Astronomical Union, 2013
ABSTRACT When galaxies merge, gas accretes onto both central supermassive black holes. Thus, one ... more ABSTRACT When galaxies merge, gas accretes onto both central supermassive black holes. Thus, one expects to see dual active galactic nuclei (AGNs) in a fraction of galaxy mergers. Candidates for galaxies containing dual AGNs have been identified by the presence of double-peaked narrow [O III] emission lines and by high spatial resolution images of close galaxy pairs. 30% of double-peaked narrow [OIII] emission line SDSS AGNs have two spatial components within a 3” radius. However, spatially resolved spectroscopy is needed to confirm these galaxy pairs as systems with double AGNs. With the Keck 2 Laser Guide Star Adaptive Optics system and the OSIRIS near-infrared integral field spectrograph, we obtained spatially resolved spectra for SDSS J09527.62+255257.2, confirming that it contains a Type 1 and a Type 2 AGN separated by 4.8 kpc (=1.0"). We performed similar observations of more spatially separated candidate dual AGNs and will report on the varied results. By assessing what fraction of radio-quiet double-peaked emission line SDSS AGNs are true dual AGNs, we can better constrain the statistics of dual AGNs and characterize physical conditions throughout these interacting AGNs.
Adaptive Optics Systems IV, 2014
A new high-order adaptive optics system is now being commissioned at the Lick Observatory Shane 3... more A new high-order adaptive optics system is now being commissioned at the Lick Observatory Shane 3-meter telescope in California. This system uses a high return efficiency sodium beacon and a combination of low and high-order deformable mirrors to achieve diffraction-limited imaging over a wide spectrum of infrared science wavelengths covering 0.8 to 2.2 microns. We present the design performance goals and the first on-sky test results. We discuss several innovations that make this system a pathfinder for next generation AO systems. These include a unique woofer-tweeter control that provides full dynamic range correction from tip/tilt to 16 cycles, variable pupil sampling wavefront sensor, new enhanced silver coatings developed at UC Observatories that improve science and LGS throughput, and tight mechanical rigidity that enables a multi-hour diffractionlimited exposure in LGS mode for faint object spectroscopy science.
Adaptive Optics Systems IV, 2014
We describe the design and first-light early science performance of the Shane Adaptive optics inf... more We describe the design and first-light early science performance of the Shane Adaptive optics infraRed Camera-Spectrograph (ShARCS) on Lick Observatory's 3-m Shane telescope. Designed to work with the new ShaneAO adaptive optics system, ShARCS is capable of high-efficiency, diffraction-limited imaging and low-dispersion grism spectroscopy in J, H, and K-bands. ShARCS uses a HAWAII-2RG infrared detector, giving high quantum efficiency (>80%) and Nyquist sampling the diffraction limit in all three wavelength bands. The ShARCS instrument is also equipped for linear polarimetry and is sensitive down to 650 nm to support future visible-light adaptive optics capability. We report on the early science data taken during commissioning.
Adaptive Optics Systems III, 2012
ABSTRACT The Lick Observatory 3-meter telescope has a history of serving as a testbed for innovat... more ABSTRACT The Lick Observatory 3-meter telescope has a history of serving as a testbed for innovative adaptive optics techniques. In 1996, it became one of the first astronomical observatories to employ laser guide star (LGS) adaptive optics as a facility instrument available to the astronomy community. Work on a second-generation LGS adaptive optics system, ShaneAO, is well underway, with plans to deploy on telescope in 2013. In this paper we discuss key design features and implementation plans for the ShaneAO adaptive optics system. Once again, the Shane 3-m will host a number of new techniques and technologies vital to the development of future adaptive optics systems on larger telescopes. Included is a woofer-tweeter based wavefront correction system incorporating a voice-coil actuated, low spatial and temporal bandwidth, high stroke deformable mirror in conjunction with a high order, high bandwidth MEMs deformable mirror. The existing dye laser, in operation since 1996, will be replaced with a fiber laser recently developed at Lawrence Livermore National Laboratories. The system will also incorporate a high-sensitivity, high bandwidth wavefront sensor camera. Enhanced IR performance will be achieved by replacing the existing PICNIC infrared array with an Hawaii 2RG. The updated ShaneAO system will provide opportunities to test predictive control algorithms for adaptive optics. Capabilities for astronomical spectroscopy, polarimetry, and visible-light adaptive optical astronomy will be supported.
Adaptive Optics Systems IV, 2014
The Lick Observatory's Shane 3-meter telescope has been upgraded with a new infrared instrument (... more The Lick Observatory's Shane 3-meter telescope has been upgraded with a new infrared instrument (ShARCS -Shane Adaptive optics infraRed Camera and Spectrograph) and dual-deformable mirror adaptive optics (AO) system (ShaneAO). We present first-light measurements of imaging sensitivity in the Ks band. We compare measured results to predicted signal-to-noise ratio and magnitude limits from modeling the emissivity and throughput of ShaneAO and ShARCS. The model was validated by comparing its results to the Keck telescope adaptive optics system model and then by estimating the sky background and limiting magnitudes for IRCAL, the previous infra-red detector on the Shane telescope, and comparing to measured, published results. We predict that the ShaneAO system will measure lower sky backgrounds and achieve 20% higher throughput across the JHK bands despite having more optical surfaces than the current system. It will enable imaging of fainter objects (by 1-2 magnitudes) and will be faster to reach a fiducial signal-to-noise ratio by a factor of 10-13. We highlight the improvements in performance over the previous AO system and its camera, IRCAL.
Astronomical Journal, 2009
Coordinates, magnitudes and spectra are presented for 39 cataclysmic variables found in Sloan Dig... more Coordinates, magnitudes and spectra are presented for 39 cataclysmic variables found in Sloan Digital Sky Survey spectra that were primarily obtained in 2006. Of these, 12 were CVs identified prior to the SDSS spectra (GY Cnc, GO Com, ST LMi, NY Ser, MR Ser, QW Ser, EU UMa, IY UMa, HS1340+1524, RXJ1610.1+0352, Boo 1, Leo 5). Follow-up spectroscopic observations of seven systems (including one from year 2005 and another from year 2004) were obtained, resulting in estimates of the orbital periods for 3 objects. The new CVs include two candidates for high inclination, eclipsing systems, 4 new Polars and three systems whose spectra clearly reveal atmospheric absorption lines from the underlying white dwarf.
The Astrophysical Journal, 2011
Active galaxies hosting two accreting and merging super-massive black holes (SMBHs) -dual Active ... more Active galaxies hosting two accreting and merging super-massive black holes (SMBHs) -dual Active Galactic Nuclei (AGN) -are predicted by many current and popular models of black hole-galaxy coevolution. We present here the results of a program that has identified a set of probable dual AGN candidates based on near Infra-red (NIR) Laser Guide-Star Adaptive Optics (LGS AO) imaging with the Keck II telescope. These candidates are selected from a complete sample of radio-quiet Quasistellar Objects (QSOs) that show double-peaked narrow AGN emission lines, drawn from the Sloan Digital Sky Survey (SDSS). Of the twelve QSOs imaged, we find six with double galaxy structure, of which four are in galaxy mergers. We measure the ionization of the two velocity components in the narrow AGN lines to test the hypothesis that both velocity components come from an active nucleus. The combination of a well-defined parent sample and high-quality imaging allows us to place constraints on the fraction of SDSS QSOs that host dual accreting black holes separated on kiloparsec (kpc) scales: ∼ 0.4%. We derive from this fraction the time spent in a QSO phase during a typical merger (the 'duty cycle') and find a value that is strongly discrepant with estimates that come from QSO space densities and galaxy merger statistics. We conclude that either a) double-peaked line selection is a highly incomplete method of finding double AGN, b) AGN activity may be suppressed in early-to mid-stage mergers, or, more likely, c) most QSOs are not associated with gas rich majormergers. Finally, we compare the SMBH mass distributions of single and dual AGN and find little difference between the two, hinting that most SMBH growth happens in the later stages of a merger process.
The Astrophysical Journal, 2010
We study Milky Way kinematics using a sample of 18.8 million main-sequence stars with r < 20 and ... more We study Milky Way kinematics using a sample of 18.8 million main-sequence stars with r < 20 and proper-motion measurements derived from SDSS and POSS astrometry, including ∼170,000 stars with radial-velocity measurements from the SDSS spectroscopic survey. Distances to stars are determined using a photometric parallax relation, covering a distance range from ∼100 pc to 10 kpc over a quarter of the sky at high Galactic latitudes (|b| > 20 • ). We find that in the region defined by 1 kpc < Z < 5 kpc and 3 kpc < R < 13 kpc, the rotational velocity for disk stars smoothly decreases, and all three components of the velocity dispersion increase, with distance from the Galactic plane. In contrast, the velocity ellipsoid for halo stars is aligned with a spherical coordinate system and appears to be spatially invariant within the probed volume. The velocity distribution of nearby (Z < 1 kpc) K/M stars is complex, and cannot be described by a standard Schwarzschild ellipsoid. For stars in a distance-limited subsample of stars (<100 pc), we detect a multimodal velocity distribution consistent with that seen by HIPPARCOS. This strong non-Gaussianity significantly affects the measurements of the velocity ellipsoid tilt and vertex deviation when using the Schwarzschild approximation. We develop and test a simple descriptive model for the overall kinematic behavior that captures these features over most of the probed volume, and can be used to search for substructure in kinematic and metallicity space. We use this model to predict further improvements in kinematic mapping of the Galaxy expected from Gaia and LSST.
The Astronomical Journal, 2010
We apply Principal Component Analysis (PCA) to ∼100,000 stellar spectra obtained by the Sloan Dig... more We apply Principal Component Analysis (PCA) to ∼100,000 stellar spectra obtained by the Sloan Digital Sky Survey (SDSS). In order to avoid strong nonlinear variation of spectra with effective temperature, the sample is binned into 0.02 mag wide intervals of the g − r color (−0.20 < g − r < 0.90, roughly corresponding to MK spectral types A3-K3), and PCA is applied independently for each bin. In each color bin, the first four eigenspectra are sufficient to describe the observed spectra within the measurement noise. We discuss correlations of eigencoefficients with metallicity and gravity estimated by the Sloan Extension for Galactic Understanding and Exploration Stellar Parameters Pipeline. The resulting high signal-to-noise mean spectra and the other three eigenspectra are made publicly available. These data can be used to generate high-quality spectra for an arbitrary combination of effective temperature, metallicity, and gravity within the parameter space probed by the SDSS. The SDSS stellar spectroscopic database and the PCA results presented here offer a convenient method to classify new spectra, to search for unusual spectra, to train various spectral classification methods, and to synthesize accurate colors in arbitrary optical bandpasses.
The Astronomical Journal, 2009
We present new K-band spectra of VY Aqr and EI Psc obtained with NIRSPEC on the Keck II telescope... more We present new K-band spectra of VY Aqr and EI Psc obtained with NIRSPEC on the Keck II telescope. We find a best-fitting spectral type of K4 for EI Psc, in agreement with the previous classification. The Keck spectrum of VY Aqr suggests an M0 spectral type, much hotter than previously derived. We re-reduce the original data for VY Aqr that were obtained using ISAAC on the Very Large Telescope (VLT) and find a best-fitting spectral type of M6 for VY Aqr. We are unable to reconcile the two data sets. We analyze new phase-resolved optical spectroscopy of VY Aqr, obtained using UVES on the VLT, to derive the mass ratio, and show that the mass of its secondary star is very likely below the stellar/substellar boundary. We also present and model phase-resolved JHK infrared light curves for both objects, and g-and I-band light curves for EI Psc. While the light curve models for EI Psc are consistent with its spectral type, we are unable to model the light curves of VY Aqr without assuming binary star parameters outside the published range for this object.
The Astronomical Journal, 2009
Coordinates, magnitudes and spectra are presented for 39 cataclysmic variables found in Sloan Dig... more Coordinates, magnitudes and spectra are presented for 39 cataclysmic variables found in Sloan Digital Sky Survey spectra that were primarily obtained in 2006. Of these, 12 were CVs identified prior to the SDSS spectra (GY Cnc, GO Com, ST LMi, NY Ser, MR Ser, QW Ser, EU UMa, IY UMa, HS1340+1524, RXJ1610.1+0352, Boo 1, Leo 5). Follow-up spectroscopic observations of seven systems (including one from year 2005 and another from year 2004) were obtained, resulting in estimates of the orbital periods for 3 objects. The new CVs include two candidates for high inclination, eclipsing systems, 4 new Polars and three systems whose spectra clearly reveal atmospheric absorption lines from the underlying white dwarf.
The Astrophysical Journal, 2011
Most massive galaxies contain supermassive black holes (SMBHs) in their cores. When galaxies merg... more Most massive galaxies contain supermassive black holes (SMBHs) in their cores. When galaxies merge, gas is driven to nuclear regions and can accrete onto the central black hole. Thus one expects to see dual AGN in a fraction of galaxy mergers. Candidates for galaxies containing dual AGN have been identified by the presence of double-peaked narrow [O III] emission lines and by high spatial resolution images of close galaxy pairs. Spatially-resolved spectroscopy is needed to confirm these galaxy pairs as systems with spatially-separated double SMBHs. With the Keck 2 Laser Guide Star Adaptive Optics system and the OSIRIS near-infrared integral field spectrograph, we obtained spatially-resolved spectra for SDSS J09527.62+255257.2, a radio-quiet quasar shown by previous imaging to consist of a galaxy and its close (1. ′′ 0) companion. We find that the main galaxy is a Type 1 AGN with both broad and narrow AGN emission lines in its spectrum, while the companion galaxy is a Type 2 AGN with narrow emission lines only. The two AGN are separated by 4.8 kpc, and their redshifts correspond to those of the double peaks of the [O III] emission line seen in the SDSS spectrum. Line diagnostics indicate that both components of the double [O III] emission lines are due to AGN photoionization. These results confirm that J0952+2552 contains two spatially-separated AGN. As one of the few confirmed dual AGN at an intermediate separation of <10 kpc, this system offers a unique opportunity to study galaxy mergers and their effect on black hole growth.
Arxiv preprint arXiv:1001.4340, 2010
arXiv:1001.4340v2 [astro-ph.SR] 26 Jan 2010 Principal Component Analysis of SDSS Stellar Spectra ... more arXiv:1001.4340v2 [astro-ph.SR] 26 Jan 2010 Principal Component Analysis of SDSS Stellar Spectra Rosalie C. McGurk, Amy E. Kimball, Zeljko Ivezic Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 ABSTRACT ... 2.3. The g − r Color Binning ...
Adaptive Optics Systems IV, 2014
We measure the long-term systematic component of the astrometric error in the GeMS MCAO system as... more We measure the long-term systematic component of the astrometric error in the GeMS MCAO system as a function of field radius and Ks magnitude. The experiment uses two epochs of observations of NGC 1851 separated by one month. The systematic component is estimated for each of three field of view cases (15'' radius, 30'' radius, and full field) and each of three distortion correction schemes: 8 DOF/chip + local distortion correction (LDC), 8 DOF/chip with no LDC, and 4 DOF/chip with no LDC. For bright, unsaturated stars with 13 < Ks < 16, the systematic component is < 0.2, 0.3, and 0.4 mas, respectively, for the 15'' radius, 30'' radius, and full field cases, provided that an 8 DOF/chip distortion correction with LDC (for the full-field case) is used to correct distortions. An 8 DOF/chip distortion-correction model always outperforms a 4 DOF/chip model, at all field positions and magnitudes and for all field-of-view cases, indicating the presence of high-order distortion changes. Given the order of the models needed to correct these distortions (~8 DOF/chip or 32 degrees of freedom total), it is expected that at least 25 stars per square arcminute would be needed to keep systematic errors at less than 0.3 milliarcseconds for multi-year programs. We also estimate the short-term astrometric precision of the newly upgraded Shane AO system with undithered M92 observations. Using a 6-parameter linear transformation to register images, the system delivers ~0.3 mas astrometric error over short-term observations of 2-3 minutes. Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/30/2015 Terms of Use: http://spiedl.org/terms Proc. of SPIE Vol. 9148 91481J-2 Proc. of SPIE Vol. 9148 91481J-7 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/30/2015 Terms of Use: http://spiedl.org/terms
We present optical spectroscopy of six short-period cataclysmic variable stars obtained with ESO&... more We present optical spectroscopy of six short-period cataclysmic variable stars obtained with ESO's 8-meter Very Large Telescope. Four of the stars and their K1 amplitudes are GW Lib, 43.3 km/s; BW Scl, 56.6 km/s; V436 Cen, 77.5 km/s; VY Aqr, 48.7 km/s; and Z Cha, 180.6 km/s. We determined the mass ratio, q, for each system, but found likely unrealistic q values for GW Lib and Z Cha. GW Lib is a low inclination system and its accretion may be more of an accretion ring than an accretion disk. Z Cha's high inclination and strong hot spot impact the determination of q. V436 Cen's spectra show a strongly- rising blue continuum and Balmer decrements HAlpha/HBeta and HDelta/HBeta indicative an optically thick disk with a hot, thin chromosphere. WZ Sge was observed soon after its 2001 superoutburst. The emission lines were strongly dominated by the S-wave component leading to a unique radial velocity curve. We can model the RV variations as a combination of the underlying, weak ...
We apply Principal Component Analysis (PCA) to ~100,000 stellar spectra obtained by the Sloan Dig... more We apply Principal Component Analysis (PCA) to ~100,000 stellar spectra obtained by the Sloan Digital Sky Survey (SDSS). In order to avoid strong non-linear variation of spectra with effective temperature, the sample is binned into 0.02 mag wide intervals of the g-r color (-0.20<g-r<0.90, roughly corresponding to MK spectral types A3 to K3), and PCA is applied independently for each bin. In each color bin, the first four eigenspectra are sufficient to describe the observed spectra within the measurement noise. We discuss correlations of eigencoefficients with metallicity and gravity estimated by the Sloan Extension for Galactic Understanding and Exploration (SEGUE) Stellar Parameters Pipeline. The resulting high signal-to-noise mean spectra and the other three eigenspectra are made publicly available. These data can be used to generate high quality spectra for an arbitrary combination of effective temperature, metallicity, and gravity within the parameter space probed by the SDSS. The SDSS stellar spectroscopic database and the PCA results presented here offer a convenient method to classify new spectra, to search for unusual spectra, to train various spectral classification methods, and to synthesize accurate colors in arbitrary optical bandpasses.
The Astrophysical Journal, Sep 1, 2011
Active galaxies hosting two accreting and merging supermassive black holes (SMBHs)---dual active ... more Active galaxies hosting two accreting and merging supermassive black holes (SMBHs)---dual active galactic nuclei (AGNs)---are predicted by many current and popular models of black-hole-galaxy co-evolution. We present here the results of a program that has identified a set of probable dual AGN candidates based on near-infrared laser guide star adaptive optics imaging with the Keck II telescope. These candidates are selected from a complete sample of radio-quiet quasi-stellar objects (QSOs) drawn from the Sloan Digital Sky Survey (SDSS), which show double-peaked narrow AGN emission lines. Of the 12 AGNs imaged, we find 6 with double galaxy structure, of which four are in galaxy mergers. We measure the ionization of the two velocity components in the narrow AGN lines to test the hypothesis that both velocity components come from an active nucleus. The combination of a well-defined parent sample and high-quality imaging allows us to place constraints on the fraction of SDSS QSOs that host dual accreting black holes separated on kiloparsec scales: ~0.3%-0.65%. We derive from this fraction the time spent in a QSO phase during a typical merger and find a value that is much lower than estimates that arise from QSO space densities and galaxy merger statistics. We discuss possible reasons for this difference. Finally, we compare the SMBH mass distributions of single and dual AGNs and find little difference between the two within the limited statistics of our program, hinting that most SMBH growth happens in the later stages of a merger process.
The Astronomical Journal
We apply Principal Component Analysis (PCA) to ~100,000 stellar spectra obtained by the Sloan Dig... more We apply Principal Component Analysis (PCA) to ~100,000 stellar spectra obtained by the Sloan Digital Sky Survey (SDSS). In order to avoid strong nonlinear variation of spectra with effective temperature, the sample is binned into 0.02 mag wide intervals of the g – r color (–0.20 < g – r < 0.90, roughly corresponding to MK spectral types A3-K3), and PCA is applied independently for each bin. In each color bin, the first four eigenspectra are sufficient to describe the observed spectra within the measurement noise. We discuss correlations of eigencoefficients with metallicity and gravity estimated by the Sloan Extension for Galactic Understanding and Exploration Stellar Parameters Pipeline. The resulting high signal-to-noise mean spectra and the other three eigenspectra are made publicly available. These data can be used to generate high-quality spectra for an arbitrary combination of effective temperature, metallicity, and gravity within the parameter space probed by the SDSS....
Astronomical Journal, 2009
We present new K-band spectra of VY Aqr and EI Psc obtained with NIRSPEC on the Keck II telescope... more We present new K-band spectra of VY Aqr and EI Psc obtained with NIRSPEC on the Keck II telescope. We find a best-fitting spectral type of K4 for EI Psc, in agreement with the previous classification. The Keck spectrum of VY Aqr suggests an M0 spectral type, much hotter than previously derived. We re-reduce the original data for VY Aqr
Hierarchical merging of smaller structures into larger ones is fundamental to galaxy evolution in... more Hierarchical merging of smaller structures into larger ones is fundamental to galaxy evolution in LambdaCDM cosmologies. The Mbh sigma relation suggests that when galaxies merge, their central supermassive black holes merge and grow as well. Using spectroscopic surveys such as SDSS and DEEP, candidates for galaxies containing two active black holes or an offset black hole have been identified by
Proceedings of the International Astronomical Union, 2013
ABSTRACT When galaxies merge, gas accretes onto both central supermassive black holes. Thus, one ... more ABSTRACT When galaxies merge, gas accretes onto both central supermassive black holes. Thus, one expects to see dual active galactic nuclei (AGNs) in a fraction of galaxy mergers. Candidates for galaxies containing dual AGNs have been identified by the presence of double-peaked narrow [O III] emission lines and by high spatial resolution images of close galaxy pairs. 30% of double-peaked narrow [OIII] emission line SDSS AGNs have two spatial components within a 3” radius. However, spatially resolved spectroscopy is needed to confirm these galaxy pairs as systems with double AGNs. With the Keck 2 Laser Guide Star Adaptive Optics system and the OSIRIS near-infrared integral field spectrograph, we obtained spatially resolved spectra for SDSS J09527.62+255257.2, confirming that it contains a Type 1 and a Type 2 AGN separated by 4.8 kpc (=1.0"). We performed similar observations of more spatially separated candidate dual AGNs and will report on the varied results. By assessing what fraction of radio-quiet double-peaked emission line SDSS AGNs are true dual AGNs, we can better constrain the statistics of dual AGNs and characterize physical conditions throughout these interacting AGNs.
Adaptive Optics Systems IV, 2014
A new high-order adaptive optics system is now being commissioned at the Lick Observatory Shane 3... more A new high-order adaptive optics system is now being commissioned at the Lick Observatory Shane 3-meter telescope in California. This system uses a high return efficiency sodium beacon and a combination of low and high-order deformable mirrors to achieve diffraction-limited imaging over a wide spectrum of infrared science wavelengths covering 0.8 to 2.2 microns. We present the design performance goals and the first on-sky test results. We discuss several innovations that make this system a pathfinder for next generation AO systems. These include a unique woofer-tweeter control that provides full dynamic range correction from tip/tilt to 16 cycles, variable pupil sampling wavefront sensor, new enhanced silver coatings developed at UC Observatories that improve science and LGS throughput, and tight mechanical rigidity that enables a multi-hour diffractionlimited exposure in LGS mode for faint object spectroscopy science.
Adaptive Optics Systems IV, 2014
We describe the design and first-light early science performance of the Shane Adaptive optics inf... more We describe the design and first-light early science performance of the Shane Adaptive optics infraRed Camera-Spectrograph (ShARCS) on Lick Observatory's 3-m Shane telescope. Designed to work with the new ShaneAO adaptive optics system, ShARCS is capable of high-efficiency, diffraction-limited imaging and low-dispersion grism spectroscopy in J, H, and K-bands. ShARCS uses a HAWAII-2RG infrared detector, giving high quantum efficiency (>80%) and Nyquist sampling the diffraction limit in all three wavelength bands. The ShARCS instrument is also equipped for linear polarimetry and is sensitive down to 650 nm to support future visible-light adaptive optics capability. We report on the early science data taken during commissioning.
Adaptive Optics Systems III, 2012
ABSTRACT The Lick Observatory 3-meter telescope has a history of serving as a testbed for innovat... more ABSTRACT The Lick Observatory 3-meter telescope has a history of serving as a testbed for innovative adaptive optics techniques. In 1996, it became one of the first astronomical observatories to employ laser guide star (LGS) adaptive optics as a facility instrument available to the astronomy community. Work on a second-generation LGS adaptive optics system, ShaneAO, is well underway, with plans to deploy on telescope in 2013. In this paper we discuss key design features and implementation plans for the ShaneAO adaptive optics system. Once again, the Shane 3-m will host a number of new techniques and technologies vital to the development of future adaptive optics systems on larger telescopes. Included is a woofer-tweeter based wavefront correction system incorporating a voice-coil actuated, low spatial and temporal bandwidth, high stroke deformable mirror in conjunction with a high order, high bandwidth MEMs deformable mirror. The existing dye laser, in operation since 1996, will be replaced with a fiber laser recently developed at Lawrence Livermore National Laboratories. The system will also incorporate a high-sensitivity, high bandwidth wavefront sensor camera. Enhanced IR performance will be achieved by replacing the existing PICNIC infrared array with an Hawaii 2RG. The updated ShaneAO system will provide opportunities to test predictive control algorithms for adaptive optics. Capabilities for astronomical spectroscopy, polarimetry, and visible-light adaptive optical astronomy will be supported.
Adaptive Optics Systems IV, 2014
The Lick Observatory's Shane 3-meter telescope has been upgraded with a new infrared instrument (... more The Lick Observatory's Shane 3-meter telescope has been upgraded with a new infrared instrument (ShARCS -Shane Adaptive optics infraRed Camera and Spectrograph) and dual-deformable mirror adaptive optics (AO) system (ShaneAO). We present first-light measurements of imaging sensitivity in the Ks band. We compare measured results to predicted signal-to-noise ratio and magnitude limits from modeling the emissivity and throughput of ShaneAO and ShARCS. The model was validated by comparing its results to the Keck telescope adaptive optics system model and then by estimating the sky background and limiting magnitudes for IRCAL, the previous infra-red detector on the Shane telescope, and comparing to measured, published results. We predict that the ShaneAO system will measure lower sky backgrounds and achieve 20% higher throughput across the JHK bands despite having more optical surfaces than the current system. It will enable imaging of fainter objects (by 1-2 magnitudes) and will be faster to reach a fiducial signal-to-noise ratio by a factor of 10-13. We highlight the improvements in performance over the previous AO system and its camera, IRCAL.
Astronomical Journal, 2009
Coordinates, magnitudes and spectra are presented for 39 cataclysmic variables found in Sloan Dig... more Coordinates, magnitudes and spectra are presented for 39 cataclysmic variables found in Sloan Digital Sky Survey spectra that were primarily obtained in 2006. Of these, 12 were CVs identified prior to the SDSS spectra (GY Cnc, GO Com, ST LMi, NY Ser, MR Ser, QW Ser, EU UMa, IY UMa, HS1340+1524, RXJ1610.1+0352, Boo 1, Leo 5). Follow-up spectroscopic observations of seven systems (including one from year 2005 and another from year 2004) were obtained, resulting in estimates of the orbital periods for 3 objects. The new CVs include two candidates for high inclination, eclipsing systems, 4 new Polars and three systems whose spectra clearly reveal atmospheric absorption lines from the underlying white dwarf.
The Astrophysical Journal, 2011
Active galaxies hosting two accreting and merging super-massive black holes (SMBHs) -dual Active ... more Active galaxies hosting two accreting and merging super-massive black holes (SMBHs) -dual Active Galactic Nuclei (AGN) -are predicted by many current and popular models of black hole-galaxy coevolution. We present here the results of a program that has identified a set of probable dual AGN candidates based on near Infra-red (NIR) Laser Guide-Star Adaptive Optics (LGS AO) imaging with the Keck II telescope. These candidates are selected from a complete sample of radio-quiet Quasistellar Objects (QSOs) that show double-peaked narrow AGN emission lines, drawn from the Sloan Digital Sky Survey (SDSS). Of the twelve QSOs imaged, we find six with double galaxy structure, of which four are in galaxy mergers. We measure the ionization of the two velocity components in the narrow AGN lines to test the hypothesis that both velocity components come from an active nucleus. The combination of a well-defined parent sample and high-quality imaging allows us to place constraints on the fraction of SDSS QSOs that host dual accreting black holes separated on kiloparsec (kpc) scales: ∼ 0.4%. We derive from this fraction the time spent in a QSO phase during a typical merger (the 'duty cycle') and find a value that is strongly discrepant with estimates that come from QSO space densities and galaxy merger statistics. We conclude that either a) double-peaked line selection is a highly incomplete method of finding double AGN, b) AGN activity may be suppressed in early-to mid-stage mergers, or, more likely, c) most QSOs are not associated with gas rich majormergers. Finally, we compare the SMBH mass distributions of single and dual AGN and find little difference between the two, hinting that most SMBH growth happens in the later stages of a merger process.
The Astrophysical Journal, 2010
We study Milky Way kinematics using a sample of 18.8 million main-sequence stars with r < 20 and ... more We study Milky Way kinematics using a sample of 18.8 million main-sequence stars with r < 20 and proper-motion measurements derived from SDSS and POSS astrometry, including ∼170,000 stars with radial-velocity measurements from the SDSS spectroscopic survey. Distances to stars are determined using a photometric parallax relation, covering a distance range from ∼100 pc to 10 kpc over a quarter of the sky at high Galactic latitudes (|b| > 20 • ). We find that in the region defined by 1 kpc < Z < 5 kpc and 3 kpc < R < 13 kpc, the rotational velocity for disk stars smoothly decreases, and all three components of the velocity dispersion increase, with distance from the Galactic plane. In contrast, the velocity ellipsoid for halo stars is aligned with a spherical coordinate system and appears to be spatially invariant within the probed volume. The velocity distribution of nearby (Z < 1 kpc) K/M stars is complex, and cannot be described by a standard Schwarzschild ellipsoid. For stars in a distance-limited subsample of stars (<100 pc), we detect a multimodal velocity distribution consistent with that seen by HIPPARCOS. This strong non-Gaussianity significantly affects the measurements of the velocity ellipsoid tilt and vertex deviation when using the Schwarzschild approximation. We develop and test a simple descriptive model for the overall kinematic behavior that captures these features over most of the probed volume, and can be used to search for substructure in kinematic and metallicity space. We use this model to predict further improvements in kinematic mapping of the Galaxy expected from Gaia and LSST.
The Astronomical Journal, 2010
We apply Principal Component Analysis (PCA) to ∼100,000 stellar spectra obtained by the Sloan Dig... more We apply Principal Component Analysis (PCA) to ∼100,000 stellar spectra obtained by the Sloan Digital Sky Survey (SDSS). In order to avoid strong nonlinear variation of spectra with effective temperature, the sample is binned into 0.02 mag wide intervals of the g − r color (−0.20 < g − r < 0.90, roughly corresponding to MK spectral types A3-K3), and PCA is applied independently for each bin. In each color bin, the first four eigenspectra are sufficient to describe the observed spectra within the measurement noise. We discuss correlations of eigencoefficients with metallicity and gravity estimated by the Sloan Extension for Galactic Understanding and Exploration Stellar Parameters Pipeline. The resulting high signal-to-noise mean spectra and the other three eigenspectra are made publicly available. These data can be used to generate high-quality spectra for an arbitrary combination of effective temperature, metallicity, and gravity within the parameter space probed by the SDSS. The SDSS stellar spectroscopic database and the PCA results presented here offer a convenient method to classify new spectra, to search for unusual spectra, to train various spectral classification methods, and to synthesize accurate colors in arbitrary optical bandpasses.
The Astronomical Journal, 2009
We present new K-band spectra of VY Aqr and EI Psc obtained with NIRSPEC on the Keck II telescope... more We present new K-band spectra of VY Aqr and EI Psc obtained with NIRSPEC on the Keck II telescope. We find a best-fitting spectral type of K4 for EI Psc, in agreement with the previous classification. The Keck spectrum of VY Aqr suggests an M0 spectral type, much hotter than previously derived. We re-reduce the original data for VY Aqr that were obtained using ISAAC on the Very Large Telescope (VLT) and find a best-fitting spectral type of M6 for VY Aqr. We are unable to reconcile the two data sets. We analyze new phase-resolved optical spectroscopy of VY Aqr, obtained using UVES on the VLT, to derive the mass ratio, and show that the mass of its secondary star is very likely below the stellar/substellar boundary. We also present and model phase-resolved JHK infrared light curves for both objects, and g-and I-band light curves for EI Psc. While the light curve models for EI Psc are consistent with its spectral type, we are unable to model the light curves of VY Aqr without assuming binary star parameters outside the published range for this object.
The Astronomical Journal, 2009
Coordinates, magnitudes and spectra are presented for 39 cataclysmic variables found in Sloan Dig... more Coordinates, magnitudes and spectra are presented for 39 cataclysmic variables found in Sloan Digital Sky Survey spectra that were primarily obtained in 2006. Of these, 12 were CVs identified prior to the SDSS spectra (GY Cnc, GO Com, ST LMi, NY Ser, MR Ser, QW Ser, EU UMa, IY UMa, HS1340+1524, RXJ1610.1+0352, Boo 1, Leo 5). Follow-up spectroscopic observations of seven systems (including one from year 2005 and another from year 2004) were obtained, resulting in estimates of the orbital periods for 3 objects. The new CVs include two candidates for high inclination, eclipsing systems, 4 new Polars and three systems whose spectra clearly reveal atmospheric absorption lines from the underlying white dwarf.
The Astrophysical Journal, 2011
Most massive galaxies contain supermassive black holes (SMBHs) in their cores. When galaxies merg... more Most massive galaxies contain supermassive black holes (SMBHs) in their cores. When galaxies merge, gas is driven to nuclear regions and can accrete onto the central black hole. Thus one expects to see dual AGN in a fraction of galaxy mergers. Candidates for galaxies containing dual AGN have been identified by the presence of double-peaked narrow [O III] emission lines and by high spatial resolution images of close galaxy pairs. Spatially-resolved spectroscopy is needed to confirm these galaxy pairs as systems with spatially-separated double SMBHs. With the Keck 2 Laser Guide Star Adaptive Optics system and the OSIRIS near-infrared integral field spectrograph, we obtained spatially-resolved spectra for SDSS J09527.62+255257.2, a radio-quiet quasar shown by previous imaging to consist of a galaxy and its close (1. ′′ 0) companion. We find that the main galaxy is a Type 1 AGN with both broad and narrow AGN emission lines in its spectrum, while the companion galaxy is a Type 2 AGN with narrow emission lines only. The two AGN are separated by 4.8 kpc, and their redshifts correspond to those of the double peaks of the [O III] emission line seen in the SDSS spectrum. Line diagnostics indicate that both components of the double [O III] emission lines are due to AGN photoionization. These results confirm that J0952+2552 contains two spatially-separated AGN. As one of the few confirmed dual AGN at an intermediate separation of <10 kpc, this system offers a unique opportunity to study galaxy mergers and their effect on black hole growth.
Arxiv preprint arXiv:1001.4340, 2010
arXiv:1001.4340v2 [astro-ph.SR] 26 Jan 2010 Principal Component Analysis of SDSS Stellar Spectra ... more arXiv:1001.4340v2 [astro-ph.SR] 26 Jan 2010 Principal Component Analysis of SDSS Stellar Spectra Rosalie C. McGurk, Amy E. Kimball, Zeljko Ivezic Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 ABSTRACT ... 2.3. The g − r Color Binning ...
Adaptive Optics Systems IV, 2014
We measure the long-term systematic component of the astrometric error in the GeMS MCAO system as... more We measure the long-term systematic component of the astrometric error in the GeMS MCAO system as a function of field radius and Ks magnitude. The experiment uses two epochs of observations of NGC 1851 separated by one month. The systematic component is estimated for each of three field of view cases (15'' radius, 30'' radius, and full field) and each of three distortion correction schemes: 8 DOF/chip + local distortion correction (LDC), 8 DOF/chip with no LDC, and 4 DOF/chip with no LDC. For bright, unsaturated stars with 13 < Ks < 16, the systematic component is < 0.2, 0.3, and 0.4 mas, respectively, for the 15'' radius, 30'' radius, and full field cases, provided that an 8 DOF/chip distortion correction with LDC (for the full-field case) is used to correct distortions. An 8 DOF/chip distortion-correction model always outperforms a 4 DOF/chip model, at all field positions and magnitudes and for all field-of-view cases, indicating the presence of high-order distortion changes. Given the order of the models needed to correct these distortions (~8 DOF/chip or 32 degrees of freedom total), it is expected that at least 25 stars per square arcminute would be needed to keep systematic errors at less than 0.3 milliarcseconds for multi-year programs. We also estimate the short-term astrometric precision of the newly upgraded Shane AO system with undithered M92 observations. Using a 6-parameter linear transformation to register images, the system delivers ~0.3 mas astrometric error over short-term observations of 2-3 minutes. Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/30/2015 Terms of Use: http://spiedl.org/terms Proc. of SPIE Vol. 9148 91481J-2 Proc. of SPIE Vol. 9148 91481J-7 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/30/2015 Terms of Use: http://spiedl.org/terms