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Papers by A. Ptak

The Astrophysical Journal, 1998

ESO ASTROPHYSICS SYMPOSIA, 2002

Using the spectra of a sample of sim\simsim28,000 nearby obscured active galaxies from Data Release 7... more Using the spectra of a sample of sim\simsim28,000 nearby obscured active galaxies from Data Release 7 of the Sloan Digital Sky Survey (SDSS), we probe the connection between AGN activity and star formation over a range of radial scales in the host galaxy. We use the extinction-corrected luminosity of the [OIII] 5007 \AA\ line as a proxy of intrinsic AGN power and supermassive black hole (SMBH) accretion rate. The star formation rates (SFRs) are taken from the MPA-JHU value-added catalog and are measured through the 3$^{\prime\prime}$ SDSS aperture. We construct matched samples of galaxies covering a range in redshifts. With increasing redshift, the projected aperture size encompasses increasing amounts of the host galaxy. This allows us to trace the radial distribution of star-formation as a function of AGN luminosity. We find that the star formation becomes more centrally concentrated with increasing AGN luminosity and Eddington ratio. This implies that such circumnuclear star formatio...

The Astrophysical Journal, 2015

The Astrophysical Journal, 2014

The Astrophysical Journal, 2012

Sensitive surveys of the X‐ray universe have been limited to small areas of the sky due to the in... more Sensitive surveys of the X‐ray universe have been limited to small areas of the sky due to the intrinsically small field of view of Wolter‐IX‐ray optics. High angular resolution is needed to achieve a low background per source, minimize source confusion, and distinguish point from extended objects. WFXT consists of three co‐aligned wide field X‐ray telescopes with a 1° field of view and a≲ 10 ″(goal of 5 ″) angular resolution (HEW) over the full field. Total effective area at 1 keV will be WFXT will perform three extragalactic surveys that will cover ...

The Astronomical Journal, 1997

This poster presents ISS-Lobster, a wide-field X-ray transient mission proposed to be deployed on... more This poster presents ISS-Lobster, a wide-field X-ray transient mission proposed to be deployed on the International Space Station. Through its unique imaging X-ray optics that allow a 30 deg by 30 deg FoV, a 1 arc min position resolution and a 10^-11 erg/(sec cm2) sensitivity in 2000 sec, ISS-Lobster will observe numerous events per year of X-ray transients related to compact objects, including: tidal disruptions of stars, supernova shock breakouts, neutron star bursts and superbursts, high redshift Gamma-Ray Bursts, and perhaps most exciting, X-ray counterparts of gravitational wave detections involving both stellar mass and supermassive black holes. A 3-axis gimbal system will allow fast pointing in response to any independent, multi-wavelength indication of these events. Finally, deployment of this detector on the ISS will realize significant cost savings compared to a free-flying satellite as power, communication, and ISS transport are provided.

Space Telescopes and Instrumentation 2010: Ultraviolet to Gamma Ray, 2010

We use deep J (1.25 mu m) and Ks (2.15 mu m) images of the Antennae (NGC 4038/9) obtained with th... more We use deep J (1.25 mu m) and Ks (2.15 mu m) images of the Antennae (NGC 4038/9) obtained with the Wide-field InfraRed Camera on the Palomar 200-inch telescope, together with the Chandra X-ray source list of Zezas et al. (2001), to establish an X-ray/IR astrometric frame tie with ˜ 0.5 " RMS residuals over a ˜ 5 ' field.

We are carrying out sensitive X-ray observations with Chandra and XMM of type II quasars selected... more We are carrying out sensitive X-ray observations with Chandra and XMM of type II quasars selected from the Sloan Digital Sky Survey based on their optical emission line properties. In this paper we present the first results of our program. We present observations of four objects at redshifts 0.4 < z < 0.8 and an analysis of the archival data

The Astrophysical Journal, 1998

ESO ASTROPHYSICS SYMPOSIA, 2002

Using the spectra of a sample of sim\simsim28,000 nearby obscured active galaxies from Data Release 7... more Using the spectra of a sample of sim\simsim28,000 nearby obscured active galaxies from Data Release 7 of the Sloan Digital Sky Survey (SDSS), we probe the connection between AGN activity and star formation over a range of radial scales in the host galaxy. We use the extinction-corrected luminosity of the [OIII] 5007 \AA\ line as a proxy of intrinsic AGN power and supermassive black hole (SMBH) accretion rate. The star formation rates (SFRs) are taken from the MPA-JHU value-added catalog and are measured through the 3$^{\prime\prime}$ SDSS aperture. We construct matched samples of galaxies covering a range in redshifts. With increasing redshift, the projected aperture size encompasses increasing amounts of the host galaxy. This allows us to trace the radial distribution of star-formation as a function of AGN luminosity. We find that the star formation becomes more centrally concentrated with increasing AGN luminosity and Eddington ratio. This implies that such circumnuclear star formatio...

The Astrophysical Journal, 2015

The Astrophysical Journal, 2014

The Astrophysical Journal, 2012

Sensitive surveys of the X‐ray universe have been limited to small areas of the sky due to the in... more Sensitive surveys of the X‐ray universe have been limited to small areas of the sky due to the intrinsically small field of view of Wolter‐IX‐ray optics. High angular resolution is needed to achieve a low background per source, minimize source confusion, and distinguish point from extended objects. WFXT consists of three co‐aligned wide field X‐ray telescopes with a 1° field of view and a≲ 10 ″(goal of 5 ″) angular resolution (HEW) over the full field. Total effective area at 1 keV will be WFXT will perform three extragalactic surveys that will cover ...

The Astronomical Journal, 1997

This poster presents ISS-Lobster, a wide-field X-ray transient mission proposed to be deployed on... more This poster presents ISS-Lobster, a wide-field X-ray transient mission proposed to be deployed on the International Space Station. Through its unique imaging X-ray optics that allow a 30 deg by 30 deg FoV, a 1 arc min position resolution and a 10^-11 erg/(sec cm2) sensitivity in 2000 sec, ISS-Lobster will observe numerous events per year of X-ray transients related to compact objects, including: tidal disruptions of stars, supernova shock breakouts, neutron star bursts and superbursts, high redshift Gamma-Ray Bursts, and perhaps most exciting, X-ray counterparts of gravitational wave detections involving both stellar mass and supermassive black holes. A 3-axis gimbal system will allow fast pointing in response to any independent, multi-wavelength indication of these events. Finally, deployment of this detector on the ISS will realize significant cost savings compared to a free-flying satellite as power, communication, and ISS transport are provided.

Space Telescopes and Instrumentation 2010: Ultraviolet to Gamma Ray, 2010

We use deep J (1.25 mu m) and Ks (2.15 mu m) images of the Antennae (NGC 4038/9) obtained with th... more We use deep J (1.25 mu m) and Ks (2.15 mu m) images of the Antennae (NGC 4038/9) obtained with the Wide-field InfraRed Camera on the Palomar 200-inch telescope, together with the Chandra X-ray source list of Zezas et al. (2001), to establish an X-ray/IR astrometric frame tie with ˜ 0.5 " RMS residuals over a ˜ 5 ' field.

We are carrying out sensitive X-ray observations with Chandra and XMM of type II quasars selected... more We are carrying out sensitive X-ray observations with Chandra and XMM of type II quasars selected from the Sloan Digital Sky Survey based on their optical emission line properties. In this paper we present the first results of our program. We present observations of four objects at redshifts 0.4 < z < 0.8 and an analysis of the archival data

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