I thank Bruce for his skillful and persistent manufacturing efforts that produced the majority of the devices presented in this thesis. Ben and I spent countless hours together in the laboratory, and I thank him for his company and for introducing me to many aspects of laboratory work and data analysis.
X-ray Surveys of Active Galaxies
These projects have resolved a significant portion of the diffuse extragalactic X-ray background (at least in the lower half of the accessible energy band — Worsley et al. 2005). Spectroscopic optical follow-up has been successful in classifying and measuring redshifts for a large fraction (more than half) of the resolved sources.
Detector Technologies for Future X-ray Surveys
A first step is to demonstrate a strip detector: a design architecture that enables efficient coupling of photon energy to the MKID for optical, UV and X-ray applications. Experimental efforts leading to the first demonstration of an MKID-based stripe detector are detailed in the second part of this thesis.
Thesis Organization
This chapter includes a discussion of the issues of sample completeness and selection effects. Finally, Chapter 9 concludes with an introduction to the fabrication techniques for MKIDs with a focus on strip detector fabrication, including a summary of the mask sets and fabrication runs important to the work presented in Chapters 10 and 11.
The Extragalactic X-Ray Background
This suggestion was ruled out by subsequent measurements of the cosmic microwave background (CMB) by the Cosmic Background Explorer (COBE) satellite (Mather et al. 1990). Corresponding optical identifications were also made, showing that the majority of the extragalactic sources were non-eclipsed quasars and Seyfert galaxies (Schmidt et al. 1998).
A New Era in X-ray Astrophysics
The effective area of the telescope optics for both image detector arrays is shown in Figure 2.4. Four of the CCDs (chips 0–3) are arranged in a square; these are called the ACIS-I array.
ACIS-S
XRB Surveys with Chandra
In this luminosity range, the source density on the sky is several hundreds per square degree, requiring surveys covering the order of a square degree or more to obtain statistically useful samples for studying source properties and population evolution. It is the coverage of this part of the phase space that is the goal of the SEXSI survey.
The SEXSI Program
Analysis and
Introduction
Exposure times of 1 m in each of two deep fields, the Chandra Deep Field-North (CDF-N; Brandt et al. 2001) and the ChandraDeep Field-South (CDF-S; Ueda et al. (2001) have recently published a catalog of 2 – 10 keV X-ray sources from the ASCA database containing 1343 sources.
Selection of Chandra Fields
Future papers will address detailed analyzes of different source populations as well as field-to-field variation. Net exposure times range from 18 ks to 186 ks; a histogram of exposure times is given in Figure 3.2.
Data Reduction and Analysis
We do this instead of extracting counts from the soft band image using the hard band positions to minimize bias, as described below. To avoid this, we use the hardness ratios derived from the independent soft and hard source catalogs.
The Source Catalog
In most of the other cases, no source was visible in the hardcover, although quite a few had paperback counterparts. In particular, we are confident that the self-consistent method we used for calculating the source detection threshold and the effective area function will yield an unbiased estimate of the true logN−logS relation for hard-band X-ray sources.
The 2 – 10 keV log N – log S Relation
Data point errors are statistical errors only and do not include estimation. Note that the normalization match between SEXSI and CDF-S data is good.
X-ray Properties of the Sample
For the HR < 0 plot (top panel), we fit the data with a single power law at the above fluxes. Sources not detected in the soft band are indicated in the text for the bottom two panels.
Summary
For a source below our threshold in the soft band, we will report a flux of zero, while CDF-S may detect a positive flux. Elise Laird and Alan Diercks greatly helped build our optical data reduction pipeline with useful code and helpful advice.
Appendix
We are very grateful to the following ChandraGuest researchers for their willingness to give us immediate access to their data for the purposes of this statistical investigation of random sources: Jan Vrtilek, Crystal Martin, and Q. SEXSI, which includes sources obtained from over 2 deg2 ofChandraimages, provides the largest hard X-ray selected sample studied so far and offers an essential complement to the Chandra deep fields (total area ~ 0.2 deg2).
Introduction
Our goal is to spectroscopically determine the redshift distributions and nature of the solid (2 – 10 keV) populations of X-ray sources from which most of the X-ray background originates. In this paper, we present R -band optical imaging of the SEXSI Chandra fields, as well as the methodology used to derive the X-ray source identification and catalog of R -band counter magnitudes.
Optical Imaging and Reduction
To determine limiting magnitudes for each image, we made histograms of the R -band source density in 0.5 size bins. Limiting magnitudes are defined by the inter-bin flux, where our number of counts goes from more than 80% to less than 80% of Capak et al.
Optical Counterparts to X-Ray Sources
The number of false matches per field depends on both the number of X-ray sources detected in the Chandra field and the optical imaging depth. For all fields tested, the number of false discoveries is consistent with the values we calculate.
The Catalog
The star value of the 8 bright sources with optflag = 3 (from the literature) is set to 1.00. Note that for all optical homologous data columns, special attention must be paid to the optical flag.
Discussion
Heavy lines indicate SEXSI sources; The lighter lines indicate sources from the CDF-N ( Alexander et al. 2003 ; Barger et al. 2003 ). This involved converting the X-ray photon indices Γ from the individually derived indices used in the CDF-N X-ray catalog ( Alexander et al. 2003 ) to the Γ = 1.5 average adopted by the SEXSI project.
Summary
This work used the USNOFS Image and Catalog Archive, maintained by the United States Naval Observatory, Flagstaff Station. The redshift distribution of these emission line galaxies peaks at a significantly lower redshift than that of the sources we identify spectroscopically as AGN.
Introduction
To achieve this, SEXSI covers more than 2 deg2 of the sky. 2003, hereafter Paper I) describes the X-ray source sample, Eckart et al. 2005, hereafter Paper II) describes optical image tracking and this paper presents optical spectroscopy results. We investigate in some detail the nature of the large sample of 168 sources classified as emission line galaxies.
Survey Design
We organize the paper as follows: §5.2 discusses the overall design of the spectroscopic follow-up program;. An additional catalog of 879 sources that have soft-band detections but lack hard-band detections is presented in the Appendix to Paper I.
Optical Spectroscopy: Data Collection and Reduction
This was the third most distant object known at the time of discovery and had interesting implications for the ionization history of the Universe (Stern et al. 2005b). The observations of each mask were divided into three exposures of 1200 s to allow rejection of cosmic rays; no dithering was done between exposures to allow easy application of the pipeline reduction software (see below).
Redshift Determination and Source Classification
These sources are the obscured AGN in the unified model (Antonucci 1993), seen at the edge with an obscured view of the core. The optical spectroscopic data starts with the redshift in column 11, followed by the classification in column 12 (see § 5.4 for details of the redshift and classification determinations).
Hard X-ray Source Population Statistics
Higher values of log(fx/fo) generally indicate more obscuration - 2 – 10 keV light is relatively unaffected by obscuring material while AGN optical light is absorbed. The upper panel shows the 2 – 10 keV luminosity distribution, while the lower panel shows the 0.5 – 2 keV distribution.
Source Classes
Most ELGs are obscured, as are NLAGNs to an even greater extent. In addition, due to the higher mean luminosity, NLAGNs are visible at higher redshift.
Selection Effects and Sample Completion
There are no DEIMOS-identified NLAGN below z = 0.8 and half of the sources are found at z >2. The first three boxes (z < 1.5) contain the majority of the open circles (non-BL sources) due to the large ELG population.
Global Characteristics of the Sample and Comparison with Other Surveyswith Other Surveys
Fraction of obscured sources as a function of observed (absorbed) 2–10 keV flux for SEXSI sources with NH calculated by X-ray spectral fitting (black) as presented in the source catalog and in this article, and from hardness ratios (grey). Figure 5.22 shows the fraction of obscured sources as a function of unobscured luminosity for sources with spectroscopic redshifts.
The Nature of the Emission-Line Galaxies
However, their X-ray luminosity falls more than an order of magnitude above the Ranalli et al. 2003) Lx/Lr correlation for starbursts. The ELG usually falls on the best-fit line from Fiore et al. (2003) but NLAGN tends to fall below the line.
Sources Associated with Target and Non-Target Galaxy ClustersClusters
Note that the individual ELG spectra show no evidence of the [Ne V]λ3426 high ionization emission line indicative of the underlying AGN activity, while the increased S/N of the stacked spectrum does show the [Ne V]λ3426 emission shows. In Paper I we marked sources when they fell within 1 moving Mpc of the cluster center, as projected onto the sky.
Summary
Including these four additional cluster AGN in our comparison of cluster member class statistics with those from the SEXSI background sample, we find an even lower fraction of cluster BLAGN: 12% ±8%. We have investigated in some detail the nature of the large sample of 168 sources that we classify as emission line galaxies.
Introduction
The selection of AGN based on IRAC colors also allows us to examine the X-ray and mid-IR selected samples and comment on the effectiveness of the IR selection technique. We first discuss the IR properties of the sample of SEXSI sources and then explore the X-ray undetected SpitzerAGN sample.
Spitzer Imaging with IRAC and MIPS
Spitzer, on the other hand, is well suited to detecting light sources, as the mid-IR radiation from the obscuring material outstrips other radiation sources regardless of viewing angle. We organize the section as follows: § 6.2 presents the mid-IR observations and data reduction; §6.3 presents the catalog; §6.4 discusses the mid-IR properties of the 2 – 10 keV SEXSI sources; § 6.5 presents the average X-ray properties of X-ray undetected Spitzer sources; § 6.6 describes future directions.
Source Catalog
X-ray Selected SEXSI Sources Viewed in the Infrared
At the highest X-ray luminosities (Lx >1043.5 erg s−1), all but two sources are consistent with the wedge. Only 5% of the optically bright 4-band IRAC sources lie in the jammed region, while 20% of the optically fainter 4-band IRAC sources do.
Mean X-ray Properties of Infrared Selected Active Galax- iesies
This trend is most significant in the hard band, where the average flux of the wedge-selected sample is over three times larger than the total sample. The stack of sources outside the wedge shows only a marginal detection in the hard band, with detection significance of 3, and source flux over six times lower than that of the wedge sources.
Conclusions and Future Work
It is possible that the cluster is missing a population of sources, such that the cluster counts are dominated by a subset of the resources selected in the wedge. In the short term, we plan to study the distribution of counts in our stack to determine if we can suggest whether the stack is dominated by a subset of clustered resources.
Scientific Motivation for Next-Generation X-ray Survey Missions
For example, Chapter5 discusses the identified sample of AGN from the SEXSI survey and compares with other Chandra and XMM-Newton surveys. Future studies should also allow detailed X-ray spectral modeling of large samples of AGN at cosmic distances; this is currently unavailable to all but the brightest sources in the X-ray sky.
Basic Design Requirements for Future X-ray Survey Mis- sionssions
