AGN Feedback: Does it work? (2009)
Mathur, Smita, Stoll, Rebecca, Krongold, Yair, Nicastro, Fabrizio, Brickhouse, Nancy, Elvis, Martin
While feedback is important in theoretical models, we do not really know if it works in reality. Feedback from jets appears to be sufficient to keep the cooling flows in clusters from cooling too...
XMM-Newton View of the Multi-Phase Warm Absorber in Seyfert 1 Galaxy NGC985 (2008)
Krongold, Yair, Jimenez-Bailon, Elena, Santos-Lleo, Maria, Nicastro, Fabrizio, Elvis, Martin, Brickhouse, Nancy, ...
We present an analysis of an XMM-Newton observation of the Seyfert 1 Galaxy NGC 985. The EPIC spectra present strong residuals to a single power-law model, indicating the presence of ionized...
A BLR origin for the iron K$\alpha$ line in NGC7213 (2008)
Bianchi, Stefano, La Franca, Fabio, Matt, Giorgio, Guainazzi, Matteo, Bailon, Elena Jimenez, Longinotti, Anna Lia, ...
The X-ray spectrum of NGC7213 is known to present no evidence for Compton reflection, a unique result among bright Seyfert 1s. The observed neutral iron K$\alpha$ line, therefore, cannot be...
Can Ionized Outflows in AGN Produce Important Feedback Effects? The Case of NGC 4051 (2008)
Elena Jiménez Bailón, Fabrizio Nicastro, Luc Binette, Martin Elvis, Nancy Brickhouse, Smita Mathur, ...
Using a 100 ks XMM-Newton exposure of the Narrow Line Seyfert 1 NGC 4051, we show that the time evolution of the ionization state of the X-ray absorbers in response to the rapid and highly variable...
Williams, Rik J., Mathur, Smita, Nicastro, Fabrizio
We search for highly-ionized gas near three AGN host galaxies using the Chandra low-energy transmission grating spectrograph. Strong absorption lines from such gas are seen at z=0, most likely from...
On the nature of the z=0 X-ray absorbers: I. Clues from an external group (2007)
Mathur, Smita, Sivakoff, Gregory R., Williams, Rik J., Nicastro, Fabrizio
Absorption lines of OVII at redshift zero are observed in high quality Chandra spectra of extragalactic sightlines. The location of the absorber producing these lines, whether from the corona of the...
Lost Baryons at Low Redshift (2007)
Mathur, Smita, Nicastro, Fabrizio, Williams, Rik J.
We review our attempts to discover lost baryons at low redshift with ``X-ray forest'' of absorption lines from the warm-hot intergalactic medium. We discuss the best evidence to date along the Mrk...
Krongold, Yair, Nicastro, Fabrizio, Elvis, Martin, Brickhouse, Nancy, Binette, Luc, Mathur, Smita, ...
(Abridged) Using a 100 ks XMM-Newton exposure of NGC 4051, we show that the time evolution of the ionization state of the X-ray absorbers in response to the rapid and highly variable X-ray continuum...
Binette, Luc, Krongold, Yair, Benitez, Erika, Humphrey, Andrew, Nicastro, Fabrizio, ...
Using Chandra and HST archival data, we have studied the individual Spectral Energy Distribution (SED) of 11 quasars. All UV spectra show a spectral break around 1100A. 5 X-ray spectra show the...
Time-Evolving Photoionization: the Thin and Compact X-Ray Wind of NGC 4051 (2007)
Nicastro, Fabrizio, Krongold, Yair, Elvis, Martin, Brickhouse, Nancy, Mathur, Smita, Binette, Luc
We discuss the power of time-evolving photoionization as a diagnostic tool to measure the electron density of photoionized gas. We apply this technique to a XMM-Newton observation of the ionized...
Williams, Rik J., Mathur, Smita, Nicastro, Fabrizio, Elvis, Martin
The X-ray bright z=0.116 quasar PKS 2155-304 is frequently observed as a Chandra calibration source, with a total of 483 ksec of Low Energy Transmission Grating (LETG) exposure time accumulated...
The weak absorbing outflow in AGN Mrk 279: evidence of super-solar metal abundances (2006)
Fields, Dale L., Mathur, Smita, Krongold, Yair, Williams, Rik, Nicastro, Fabrizio
We present analysis and photoionization modeling of the Chandra high resolution spectrum of Mrk 279. There is clear evidence of an absorbing outflow which is best fit by a two component model, one...
XMM-Newton View of the z>0 Warm-Hot Intergalactic Medium Toward Markarian 421 (2006)
Williams, Rik J., Mathur, Smita, Nicastro, Fabrizio, Elvis, Martin
The recent detection with Chandra of two warm-hot intergalactic medium (WHIM) filaments toward Mrk 421 by Nicastro et al. provides a measurement of the bulk of the "missing baryons" in the nearby...
Chandra Detection of Local Warm-Hot Gas Toward Markarian 279 (2005)
Williams, Rik J., Mathur, Smita, Nicastro, Fabrizio
We report the Chandra detection of OVII K\alpha absorption at z=0 in the direction of the z=0.03 Seyfert 1 galaxy Mkn 279. The high velocity cloud Complex C lies along this line of sight, with HI...
Galactic Corona or Local Group Intergalactic Medium? (2005)
Williams, Rik J., Mathur, Smita, Nicastro, Fabrizio
Cosmological hydrodynamic simulations predict that the low redshift universe comprises a web of warm-hot intergalactic gas and galaxies, with groups of galaxies and clusters forming at dense knots in...
Probing the Local Group Medium Toward Mkn 421 with Chandra and FUSE (2005)
Williams, Rik J., Mathur, Smita, Nicastro, Fabrizio, Elvis, Martin, Drake, Jeremy J., Fang, Taotao, ...
We report the detection of highly-ionized gas at z~0 seen in resonant UV and X-ray absorption lines toward the z=0.03 blazar Mkn 421. A total of 13 X-ray and 3 UV lines were measured (or upper limits...
Chandra Detection of the First X-ray Forest along the Line of Sight To Mkn 421 (2005)
Nicastro, Fabrizio, Mathur, Smita, Elvis, Martin, Drake, Jeremy, Fiore, Fabrizio, Fang, Taotao, ...
We present the first >=3.5 sigma (conservative) or >=5.8 sigma (sum of lines significance) detection of two Warm-Hot Intergalactic Medium (WHIM) filaments at z>0, which we find along the line of...
Super-solar Metallicity in the NLS1 Galaxy Markarian 1044 (2005)
Fields, Dale L., Mathur, Smita, Pogge, Richard W., Nicastro, Fabrizio, Komossa, Stefanie, Krongold, Yair
The determination of the bulk metallicity and the abundance mixture of various elements is very difficult in quasars and AGNs because only a few lines are observed and the ionization correction is...
Measured Cosmological Mass Density in the WHIM: the Solution to the 'Missing Baryons' Problem (2005)
Nicastro, Fabrizio, Elvis, Martin, Fiore, Fabrizio, Mathur, Smita
We review the current high-significance X-ray detections of Warm-Hot Intergalactic Medium (WHIM) filaments at z>0 along the lines of sight to the two blazars Mrk 421 (z=0.03) and 1ES 1028+511...
Supersolar N/C in the narrow-line Seyfert 1 galaxy markarian 1044 (2005)
Fields, Dale L., Mathur, Smita, Pogge, Richard W., Nicastro, Fabrizio, Komossa, Stefanie
Supersolar metallicity in the NLS1 galaxy markarian 1044 (2005)
Fields, Dale L., Mathur, Smita, Pogge, Richard W., Nicastro, Fabrizio, Komossa, Stefanie, Krongold, Yair
Fe XXV and Fe XXVI lines from low velocity, photoionised gas in the X-ray spectra of AGN (2004)
Bianchi, Stefano, Matt, Giorgio, Nicastro, Fabrizio, Porquet, Delphine, Dubau, Jacques
We have calculated the equivalent widths of the absorption lines produced by Fe XXV and Fe XXVI in a Compton-thin, low-velocity photoionised material illuminated by the nuclear continuum in AGN. The...
Super-solar N/C in the NLS1 Galaxy Markarian 1044 (2004)
Fields, Dale L., Mathur, Smita, Pogge, Richard W., Nicastro, Fabrizio, Komossa, Stefanie
Narrow-Line Seyfert 1s (NLS1s) are known to have extreme values of a number of properties compared to Active Galactic Nuclei (AGN) as a class. In particular, previous emission-line studies have...
The X-ray absorber of PKS2126-158 (2003)
Fiore, Fabrizio, Elvis, Martin, Maiolino, Roberto, Nicastro, Fabrizio, Siemiginowska, Aneta, Stratta, Giulia, ...
BeppoSAX observed the z=3.27 quasar PKS2126-158 on 1999 May 24-28 when its 2-10keV and 0.1-2.5keV fluxes were 1.1E-11 and 4.4E-12 cgs respectively, a factor of 2 higher than in all previous ROSAT and...
Chandra and FUSE view of the WHIM: the Local Group and beyond (2003)
Abstract. In this contribution, I review the current observational evidence for the existence of filaments of Warm-Hot Intergalactic Medium (WHIM). In particular, I first focus on the controversial...
ROSAT Blank Field Sources I: Sample Selection and Archival Data (2002)
Cagnoni, Ilaria, Elvis, Martin, Kim, Dong-Woo, Nicastro, Fabrizio, Celotti, Annalisa
We have identified a population of blank field sources (or `blanks') among the ROSAT bright unidentified X-ray sources with faint optical counterparts. The extreme X-ray over optical flux ratio of...
Blank field X-ray sources (2001)
Cagnoni, Ilaria, Celotti, Annalisa, Elvis, Martin, Dong-Woo Kim, Nicastro, Fabrizio
The X-ray sky is not as well known as is sometimes thought. We report on our search of minority populations (Kim & Elvis 1999). One of the most intriguing is that of `blank field sources', i.e....
BeppoSAX Observations of the Maser Sy2 Galaxy: ESO103-G35 (2000)
Wilkes, Belinda J., Mathur, Smita, Fiore, Fabrizio, Antonelli, Angelo, Nicastro, Fabrizio
We have made BeppoSAX observations of the Seyfert 2/1.9 galaxy ESO103-G35, which contains a nuclear maser source and is known to be heavily absorbed in the X-rays. Analysis of the X-ray spectra...
Blank Field X-Ray Sources (2000)
Cagnoni, Ilaria, Celotti, Annalisa, Elvis, Martin, Kim, Dong-Woo, Nicastro, Fabrizio
The X-ray sky is not as well known as is sometimes thought. We report on our search of minority populations (Kim & Elvis 1999). One of the most intriguing is that of `blank field sources', i.e....
Nicastro, Fabrizio, Fiore, Fabrizio, Matt, Giorgio
We present photoionization models accounting for both photoelectric and resonant absorption. Resonance absorption lines from C, O, Ne, Mg, Si S and Fe between 0.1 and 10 keV are treated. In...
The variability properties of X-ray steep and X-ray flat quasars (1998)
Fiore, Fabrizio, Laor, Ari, Elvis, Martin, Nicastro, Fabrizio, Giallongo, Emanuele
We have studied the variability of 6 low redshift, radio quiet `PG' quasars on three timescales (days, weeks, and months) using the ROSAT HRI. The quasars were chosen to lie at the two extreme ends...