We report exploratory Chandra observations of the ultraluminous quasar SDSS J010013.02+280225.8 at redshift 6.30. The quasar is clearly detected by Chandra with a possible component of extended emission. The rest-frame 2-10 keV luminosity is 9.0(+4.5)(+9.1) x 10(45) erg s(-1) with an inferred photon index of G = 3.03(-0.70)(+0.78). This quasar is X-ray bright, with an inferred X-ray-to-optical flux ratio alpha(ox) = -1.22(-0.05)(+0.07), higher than the values found in other quasars of comparable ultraviolet luminosity. The properties inferred from this exploratory observation indicate that this ultraluminous quasar might be growing with super-Eddington accretion and probably viewed with a small inclination angle. Deep X-ray observations will help to probe the plausible extended emission and better constrain the spectral features for this ultraluminous quasar.

No description available.

According to current cosmological theory, the rate of expansion of the universe depends on the average energy densities of matter, radiation, and a possible vacuum energy described by a cosmological constant, &Lambda;, in the Einstein equation.<p>Observations of galaxies and radiation, along with an assumption that we hold no special place in the universe, imply an isotropic and homogeneous energy distribution, for which the universal rate of expansion for most of the history of the universe may be constructed to depend only on present values of the dimensionless matter and vacuum energy density parameters, &Omega;_M and &Omega;_&Lambda;, respectively, and the present rate of expansion of the universe, H₀. Over the past decade, much progress has been made in determining the values of the three density parameters using a variety of independent methods. In particular, observations of type Ia supernovae in the late 1990s provided the first evidence that &Lambda; &ne; 0 and that universal expansion is accelerating.<p>This study has determined values for &Omega;_M and &Omega;_&Lambda; using the brightest quasars in the Sloan Digital Sky Survey Data Release 5, which are located at a range of distances - equivalently, a range of lookback times - that have not been accessible through any other observations. After fitting the apparent magnitudes of the brightest quasars at various redshifts to the distance modulus equation with a luminosity evolution term, values for the density parameters were determined to be &Omega;_M = 0.07 and &Omega;_&Lambda; = 1.13.

According to current cosmological theory, the rate of expansion of the universe depends on the average energy densities of matter, radiation, and a possible vacuum energy described by a cosmological constant, &Lambda;, in the Einstein equation.<p>Observations of galaxies and radiation, along with an assumption that we hold no special place in the universe, imply an isotropic and homogeneous energy distribution, for which the universal rate of expansion for most of the history of the universe may be constructed to depend only on present values of the dimensionless matter and vacuum energy density parameters, &Omega;_M and &Omega;_&Lambda;, respectively, and the present rate of expansion of the universe, H₀. Over the past decade, much progress has been made in determining the values of the three density parameters using a variety of independent methods. In particular, observations of type Ia supernovae in the late 1990s provided the first evidence that &Lambda; &ne; 0 and that universal expansion is accelerating.<p>This study has determined values for &Omega;_M and &Omega;_&Lambda; using the brightest quasars in the Sloan Digital Sky Survey Data Release 5, which are located at a range of distances - equivalently, a range of lookback times - that have not been accessible through any other observations. After fitting the apparent magnitudes of the brightest quasars at various redshifts to the distance modulus equation with a luminosity evolution term, values for the density parameters were determined to be &Omega;_M = 0.07 and &Omega;_&Lambda; = 1.13.

Thesis (Ph. D.)--Ohio State University, 2004. / Title from first page of PDF file. Document formatted into pages; contains xiv, 250 p.; also includes graphics (some col). Includes abstract and vita. Advisor: Terry Walker, Dept. of Physics. Includes bibliographical references (p. 227-250).

No description available.

Αντικείμενο της εργασίας είναι η φυσική των κβάζαρς με έμφαση στη μελέτη του φαινομένου των πιδάκων. Στο πρώτο κεφάλαιο γίνεται μια εισαγωγή στους γαλαξίες και στις μελανές οπές. Το δεύτερο κεφάλαιο αναφέρεται στην φυσική των γαλαξιών. Με τη χρήση μαθηματικών μοντέλων εξηγείται η δημιουργία τους, ο σχηματισμός τους, οι κινήσεις και η ταξινόμηση τους. Επίσης, γίνεται μια εισαγωγή στους ενεργούς γαλαξιακούς πυρήνες. Το τρίτο κεφάλαιο είναι αφιερωμένο στις μελανές οπές. Η περιγραφή τους γίνεται στα πλαίσια της Γενικής Θεωρίας της Σχετικότητας. Περιγράφεται ο σχηματισμός τους, τα διαφορετικά είδη μελανών οπών καθώς και πώς αυτές αλληλεπιδρούν με το περιβάλλον στο οποίο βρίσκονται. Το τέταρτο κεφάλαιο εστιάζει στο αστρικό σύστημα που επιλέξαμε να μελετήσουμε. Περιγράφονται κβάζαρς, υπερμαζικές μελανές οπές, δίσκοι προσαύξησης και πίδακες. Το πέμπτο και τελευταίο κεφάλαιο περιέχει τα αποτελέσματα και συμπεράσματά μας, καθώς και τα μαθηματικά εργαλεία που χρησιμοποιήσαμε. Επιλέξαμε να εστιάσουμε στο πρόβλημα της καμπύλωσης των πιδάκων. Ερευνήθηκαν οι περιπτώσεις για 1) καμπύλωση λόγω ύπαρξης νέφους στο γαλαξιακό κέντρο, και 2) καμπύλωση λόγω σχετικής κίνησης του γαλαξία. Για την πρώτη περίπτωση, επιλέξαμε να προσεγγίσουμε ένα μοντέλο από την βιβλιογραφία, υποθέτοντας ότι η ταχύτητα του πίδακα μεταβάλλεται. Παρουσιάζονται τα αποτελέσματα και γίνεται σύγκριση με παρατηρησιακά δεδομένα. Για την δεύτερη περίπτωση, μελετήθηκαν πραγματικά συστήματα στα σμήνη γαλαξιών Abell 2220 και Abell 1446 και ακολουθήθηκε η προηγούμενη διαδικασία. Για την κατασκευή του κώδικα χρησιμοποιήθηκαν οι Fortran G95 και η βιβλιοθήκη Slatec, ενώ, επιπλέον, για τους αριθμητικούς υπολογισμούς τα προγράμματα Wolfram-Alpha, Maxima και Maple-Calculator. Οι υποθέσεις και τα συμπεράσματά μας βρίσκονται σε συμφωνία με την σχετική βιβλιογραφία. / The aim of this work is to study the physics of quasars with emphasis on the associated jets. In the rst chapter, there is an introduction on galaxies and black holes. The second chapter deals with the physics of galaxies. Using mathematical models, we discuss how they are created, shaped, moving and classi ed. There is also an introduction to active galactic nuclei. In the third chapter we discuss on black holes. With the using the general theory of relativity , we describe how they are created, their di erent kinds, and how black holes interact with their environment. The fourth chapter focuses on the system particular of our study. There is a discussion on quasars, super massive black holes, accretion disks, and jets. The fth and nal chapter presents our results and conclusions, as well as the mathematical tools used. We focus on the problem of the curvature of the jets. We study the cases of 1) curvature due to the existence of a nebula within the galactic center, and 2) curvature due to the relative motion of the galaxy. For the rst case, we chose to treat a model from the bibliography, assuming that the speed of the jet is not constant. We present our results and compare them with respective observational data. For the second case, we study two systems in the galaxy clusters of Abell 2220 and Abell 1446 and follow the procedure discussed above. For the construction of our code we use Fortran G95 and the library Slatec, and for auxiliary calculations the programs: Wolfram-Alpha, Maxima and Maple Calculator.

Thesis (M.Sc.)--York University, 2007. Graduate Programme in Physics and Astronomy. / Typescript. Includes bibliographical references (leaves 105-109). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:MR38804

No description available.

Quasars are galaxies hosting accreting supermassive black holes; due to their brightness, they are unique probes of the early universe. To date, only a few quasars have been reported at z > 6.5 (< 800 Myr after the big bang). In this work, we present six additional z greater than or similar to 6.5 quasars discovered using the Pan-STARRS1 survey. We use a sample of 15 z greater than or similar to 6.5 quasars to perform a homogeneous and comprehensive analysis of this highest-redshift quasar population. We report four main results: (1) the majority of z greater than or similar to 6.5 quasars show large blueshifts of the broad C IV lambda 1549 emission line compared to the systemic redshift of the quasars, with a median value similar to 3x higher than a quasar sample at z similar to 1; (2) we estimate the quasars' black hole masses (M-BH similar to (0.3-5) x. 10(9) M circle dot) via modeling of the Mg II lambda 2798 emission line and rest-frame UV continuum and find that quasars at high redshift accrete their material (with <(Lbol L-Edd)> = 0.39) at a rate comparable to a luminosity-matched sample at lower redshift, albeit with significant scatter (0.4 dex); (3) we recover no evolution of the Fe II/Mg II abundance ratio with cosmic time; and (4) we derive near-zone sizes and, together with measurements for z similar to 6 quasars from recent work, confirm a shallow evolution of the decreasing quasar near-zone sizes with redshift. Finally, we present new millimeter observations of the [C II] 158 mu m emission line and underlying dust continuum from NOEMA for four quasars and provide new accurate redshifts and [C II]/infrared luminosity estimates. The analysis presented here shows the large range of properties of the most distant quasars.