X-ray and Infrared Diagnostics of Star Formation and Black Hole Accretion in Galaxies

Persistent Link:
http://hdl.handle.net/10150/194457
Title:
X-ray and Infrared Diagnostics of Star Formation and Black Hole Accretion in Galaxies
Author:
Rigby, Jane Rebecca
Issue Date:
2006
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
Using infrared and X-ray diagnostics, we study star--formation and black hole accretion in nearby and distant galaxies.We examine diagnostics of the hardness of the ionizing field in low--redshift starburst galaxies, to constrain the initial mass function. We obtain new measurements of HeI 1.7 micron/Br 10, a physically simple diagnostic, then test ISO mid--infrared line ratios, finding them reliable. Compared to new photoionization models, the ISO ratios in 27 nearby starburst galaxies are systematically low. This argues that solar--metallicity starbursts are deficient in massive stars, or that such stars are present but highly embedded.Using Spitzer, HST, Chandra, and ground-based data, we examine the multi-wavelength (0.4--24 micron) spectral energy distributions and X-ray properties of X-ray--selected active galactic nuclei (AGN) in several deep fields: the Chandra Deep Field South, the Lockman Hole, and the extended Groth Strip. We examine the 24 micron to X-ray flux and luminosity ratios for 157 AGN at z~1; the luminosity ratios have not strongly evolved since z~0, and we find no trend with X-ray column density. This means that highly--obscured AGN do not have exceptional infrared fluxes. We examine the SEDs of 45 bright X-ray and 24 micron sources: only 22% are classified as unobscured ``type 1'' AGN; 18% are classified as ULIRG-like SEDs; and the majority are classified as obscured (``type 2'') AGN or spiral--like SEDs. This supports the picture from X-ray surveys that much of the AGN activity in the distant universe is significantly obscured. We examine why 20% of X-ray--selected AGN are optically--faint; they lie at significantly higher redshifts (median z=1.6) than most X-ray--selected AGN, and their spectra are intrinsically red. Their contribution to the X-ray Seyfert luminosity function is comparable to that of optically--bright AGN at z>1, but they do not significantly alter the redshift distribution. Lastly, we investigate why half of X-ray--selected AGN lack signs of accretion in optical spectra. We find that these ``optically--dull'' AGN have Seyfert--like mid--infrared emission, which argues that they do not have abnormally--weak UV/optical continua. The axis ratios of their host galaxies argue that extinction by host galaxies plays a key role in hiding nuclear emission lines.
Type:
text; Electronic Dissertation
Keywords:
Astronomy
Degree Name:
PhD
Degree Level:
doctoral
Degree Program:
Astronomy; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Rieke, George H
Committee Chair:
Rieke, George H

Full metadata record

DC FieldValue Language
dc.language.isoENen_US
dc.titleX-ray and Infrared Diagnostics of Star Formation and Black Hole Accretion in Galaxiesen_US
dc.creatorRigby, Jane Rebeccaen_US
dc.contributor.authorRigby, Jane Rebeccaen_US
dc.date.issued2006en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractUsing infrared and X-ray diagnostics, we study star--formation and black hole accretion in nearby and distant galaxies.We examine diagnostics of the hardness of the ionizing field in low--redshift starburst galaxies, to constrain the initial mass function. We obtain new measurements of HeI 1.7 micron/Br 10, a physically simple diagnostic, then test ISO mid--infrared line ratios, finding them reliable. Compared to new photoionization models, the ISO ratios in 27 nearby starburst galaxies are systematically low. This argues that solar--metallicity starbursts are deficient in massive stars, or that such stars are present but highly embedded.Using Spitzer, HST, Chandra, and ground-based data, we examine the multi-wavelength (0.4--24 micron) spectral energy distributions and X-ray properties of X-ray--selected active galactic nuclei (AGN) in several deep fields: the Chandra Deep Field South, the Lockman Hole, and the extended Groth Strip. We examine the 24 micron to X-ray flux and luminosity ratios for 157 AGN at z~1; the luminosity ratios have not strongly evolved since z~0, and we find no trend with X-ray column density. This means that highly--obscured AGN do not have exceptional infrared fluxes. We examine the SEDs of 45 bright X-ray and 24 micron sources: only 22% are classified as unobscured ``type 1'' AGN; 18% are classified as ULIRG-like SEDs; and the majority are classified as obscured (``type 2'') AGN or spiral--like SEDs. This supports the picture from X-ray surveys that much of the AGN activity in the distant universe is significantly obscured. We examine why 20% of X-ray--selected AGN are optically--faint; they lie at significantly higher redshifts (median z=1.6) than most X-ray--selected AGN, and their spectra are intrinsically red. Their contribution to the X-ray Seyfert luminosity function is comparable to that of optically--bright AGN at z>1, but they do not significantly alter the redshift distribution. Lastly, we investigate why half of X-ray--selected AGN lack signs of accretion in optical spectra. We find that these ``optically--dull'' AGN have Seyfert--like mid--infrared emission, which argues that they do not have abnormally--weak UV/optical continua. The axis ratios of their host galaxies argue that extinction by host galaxies plays a key role in hiding nuclear emission lines.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjectAstronomyen_US
thesis.degree.namePhDen_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineAstronomyen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorRieke, George Hen_US
dc.contributor.chairRieke, George Hen_US
dc.contributor.committeememberStrittmatter, Peteren_US
dc.contributor.committeememberBechtold, Jillen_US
dc.contributor.committeememberFan, Xiaohuien_US
dc.contributor.committeememberGreen, Richarden_US
dc.identifier.proquest1457en_US
dc.identifier.oclc137356859en_US
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