Volonteri, Marta, Natarajan, Priyamvada
In this paper, we explore the establishment and evolution of the empirical correlation between black hole mass and velocity dispersion with redshift. We track the growth and accretion history of...
The Survival of Dark Matter Halos in the Cluster Cl 0024+16 (2009)
Natarajan, Priyamvada, Kneib, Jean-Paul, Smail, Ian, Treu, Tommaso, Ellis, Richard, Moran, Sean, ...
Theories of structure formation in a cold dark matter dominated universe predict that massive clusters of galaxies assemble from the hierarchical merging of lower mass subhalos. Exploiting strong and...
Oguri, Masamune, Hennawi, Joseph F., Gladders, Michael D., Dahle, Haakon, Natarajan, Priyamvada, Dalal, Neal, ...
We derive radial mass profiles of four strong lensing selected clusters which show prominent giant arcs (Abell 1703, SDSS J1446+3032, SDSS J1531+3414, and SDSS J2111-0115), by combining detailed...
Angular momentum and clustering properties of early dark matter halos (2008)
Davis, Andrew J., Natarajan, Priyamvada
In this paper we study the angular momentum properties of simulated dark matter halos at high redshift that likely host the first stars in the Universe. Calculating the spin distributions of these...
The abundance of lensing protoclusters (2008)
D'Aloisio, Anson, Furlanetto, Steven R., Natarajan, Priyamvada
Weak gravitational lensing provides a potentially powerful method for the detection of clusters. In addition to cluster candidates, a large number of objects with possibly no optical or X-ray...
Is there an upper limit to black hole masses? (2008)
Natarajan, Priyamvada, Treister, Ezequiel
We make a case for the existence for ultra-massive black holes (UMBHs) in the Universe, but argue that there exists a likely upper limit to black hole masses of the order of $M \sim 10^{10} \msun$....
MOND plus classical neutrinos not enough for cluster lensing (2008)
Natarajan, Priyamvada, Zhao, Hongsheng
Clusters of galaxies offer a robust test bed for probing the nature of dark matter that is insensitive to the assumption of the gravity theories. Both Modified Newtonian Dynamics (MOND) and General...
The Observatory for Multi-Epoch Gravitational Lens Astrophysics (OMEGA) (2008)
Moustakas, Leonidas A, Bolton, Adam J, Booth, Jeffrey T, Bullock, James S, Cheng, Edward, Coe, Dan, ...
(abridged) The Observatory for Multi-Epoch Gravitational Lens Astrophysics (OMEGA) is a mission concept for a 1.5-m near-UV through near-IR space observatory that will be dedicated to frequent...
WMAP5 and the Cluster Mass Function (2008)
Rines, Kenneth, Diaferio, Antonaldo, Natarajan, Priyamvada
The recently revised cosmological constraints from the Five-Year WMAP data ameliorate previous tension between cosmological constraints from the microwave background and from cluster abundances. We...
A new survey for giant arcs (2008)
Hennawi, Joseph F., Gladders, Michael D., Oguri, Masamune, Dalal, Neal, Koester, Benjamin, Natarajan, Priyamvada, ...
We report on the first results of an imaging survey to detect strong gravitational lensing targeting the richest clusters selected from the photometric data of the Sloan Digital Sky Survey (SDSS)...
The Observatory for Multi-Epoch Gravitational Lens Astrophysics (OMEGA) (2008)
Moustakas, Leonidas A., Bolton, Adam J., Booth, Jeffrey T., Bullock, James S., Cheng, Edward, Coe, Dan, ...
Consequences of dark matter self-annihilation for galaxy formation (2008)
Natarajan, Priyamvada, Croton, Darren, Bertone, Gianfranco
Galaxy formation requires a process that continually heats gas and quenches star formation in order to reproduce the observed shape of the luminosity function of bright galaxies. To accomplish this,...
The survival of dark matter halos in the cluster Cl0024+16 (2007)
Natarajan, Priyamvada, Kneib, Jean-Paul, Smail, Ian, Treu, Tommaso, Ellis, Richard, Moran, Sean, ...
Theories of structure formation in a cold dark matter dominated Universe predict that massive clusters of galaxies assemble from the hierarchical merging of lower mass subhalos. Exploiting strong and...
Estimating the Mass Density of Neutral Gas At (2007)
Priyamvada Natarajan, Max Pettini
We use the relationships between galactic H I mass and B-band luminosity determined by Rao & Briggs to recalculate the mass density of neutral gas at the present epoch based on more recent...
High-Redshift Galaxies, Their Active Nuclei and Central Black Holes (2007)
Martin Haehnelt, Priyamvada Natarajan, Martin J. Rees
We demonstrate that the luminosity function of the recently detected population of actively star-forming galaxies at redshift three and the B-band QSO luminosity function at the same redshift can...
Priyamvada Natarajan, Jens Hjorth, Eelco Van Kampen
We present the results of an attempt to adapt the distribution function formalism to characterize large-scale structures like clusters of galaxies that form in a cosmological Nbody simulation. While...
Consequences of dark matter self-annihilation for galaxy formation (2007)
Natarajan, Priyamvada, Croton, Darren, Bertone, Gianfranco
Galaxy formation requires a process that continually heats gas and quenches star formation in order to reproduce the observed shape of the luminosity function of bright galaxies. To accomplish this,...
The galaxy octopole moment as a probe of weak lensing shear fields (2007)
Goldberg, David, Natarajan, Priyamvada
In this paper, we introduce the octopole moment of the light distribution in galaxies as a probe of the weak lensing shear field. While traditional ellipticity estimates of the local shear derived...
Limousin, Marceau, Sommer-Larsen, Jesper, Natarajan, Priyamvada, Milvang-Jensen, Bo
We analyze high resolution, N-body hydrodynamical simulations of fiducial galaxy clusters to probe tidal stripping of the dark matter subhalos. These simulations include a prescription for star...
How robust are the constraints on cosmology and galaxy evolution from the lens-redshift test? (2007)
Capelo, Pedro R., Natarajan, Priyamvada
The redshift distribution of galaxy lenses in known gravitational lens systems provides a powerful test that can potentially discriminate amongst cosmological models. However, applications of this...
The Observed Concentration-Mass Relation for Galaxy Clusters (2007)
Comerford, Julia M., Natarajan, Priyamvada
The properties of clusters of galaxies offer key insights into the assembly process of structure in the universe. Numerical simulations of cosmic structure formation in a hierarchical, dark matter...
The mass function of high redshift seed black holes (2007)
Lodato, Giuseppe, Natarajan, Priyamvada
In this paper we derive the mass function of seed black holes that result from the central mass concentrated via disc accretion in collapsed haloes at redshift $z\approx 15$. Using standard arguments...
Substructure in lensing clusters and simulations (2007)
Natarajan, Priyamvada, De Lucia, Gabriella, Springel, Volker
A New Survey for Giant Arcs (2006)
Hennawi, Joseph F., Gladders, Michael D., Oguri, Masamune, Dalal, Neal, Koester, Benjamin, Natarajan, Priyamvada, ...
We report on the first results of an imaging survey to detect strong gravitational lensing targeting the richest clusters selected from the photometric data of the Sloan Digital Sky Survey (SDSS)...
Strong lensing statistics in large, z~ (2006)
Moeller, Ole, Kitzbichler, Manfred, Natarajan, Priyamvada
We calculate the expected lensing statistics of the galaxy population in large, low-redshift surveys. Galaxies are modeled using realistic, multiple components: a dark matter halo, a bulge component...
The Virial Mass Function of Nearby SDSS Galaxy Clusters (2006)
Rines, Kenneth, Diaferio, Antonaldo, Natarajan, Priyamvada
We present a new determination of the cluster mass function and velocity dispersion function in a volume $\sim10^7 h^3$Mpc$^{-3}$ using the Fourth Data Release of the Sloan Digital Sky Survey (SDSS)....
Substructure and the Cusp and Fold Relations (2006)
Aazami, Amir Babak, Natarajan, Priyamvada
Gravitational lensing of a background source by a foreground galaxy lens occasionally produces four images of the source. The cusp and the fold relations impose conditions on the ratios of...
Cosmography with cluster strong lensing (2006)
Gilmore, James, Natarajan, Priyamvada
By stacking an ensemble of strong lensing clusters, we demonstrate the feasibility of placing constraints on the dark energy equation of state. This is achieved by using multiple images of sources at...
Galaxy orbits and the intracluster gas temperature in clusters (2006)
Benatov, Latchezar, Rines, Ken, Natarajan, Priyamvada, Kravtsov, Andrey, Nagai, Daisuke
In this paper we examine how well galaxies and intra-cluster gas trace the gravitational potential of clusters. Utilizing mass profiles derived from gravitational lensing and X-ray observations,...
Substructure in lensing clusters and simulations (2006)
Natarajan, Priyamvada, De Lucia, Gabriella, Springel, Volker
We present high-resolution mass reconstructions for five massive cluster-lenses spanning a redshift range from $z = 0.18$--0.57 utilising archival {\it Hubble Space Telescope} ({\it HST}) data and...
Limousin, Marceau, Kneib, Jean Paul, Natarajan, Priyamvada
We present a maximum-likelihood analysis of galaxy-galaxy lensing effects in galaxy clusters and in the field. The aim is to determine the accuracy and robustness of constraints that can be obtained...
Eccentricity of supermassive black hole binaries coalescing from gas rich mergers (2005)
Armitage, Philip J., Natarajan, Priyamvada
Angular momentum loss to circumbinary gas provides a possible mechanism for overcoming the `last parsec' problem and allowing the most massive black hole binaries formed from galactic mergers to...
The redshift distribution of gamma-ray bursts revisited (2005)
Natarajan, Priyamvada, Albanna, Badr, Hjorth, Jens, Ramirez-Ruiz, Enrico, Tanvir, Nial, Wijers, Ralph
In this letter, we calculate the redshift distribution of gamma-ray bursts assuming that they trace (i) the globally averaged star formation rate or (ii) the average metallicity in the Universe....
Abundance of substructure in clusters of galaxies (2004)
Natarajan, Priyamvada, Springel, Volker
It is widely recognized that cold dark matter models predict abundant dark matter substructure in halos of all sizes. Galaxy-galaxy lensing provides a unique opportunity to directly measure the...
Quantifying Substructure Using Galaxy-Galaxy Lensing in Distant Clusters (2004)
Natarajan, Priyamvada, Kneib, Jean-Paul, Smail, Ian, Ellis, Richard
We present high-resolution mass reconstructions for five massive cluster-lenses spanning a redshift range from z = 0.18 - 0.57 utilizing archival Hubble Space Telescope data and applying...
Limousin, Marceau, Kneib, Jean Paul, Natarajan, Priyamvada
We present a maximum-likelihood analysis of galaxy-galaxy lensing effects in galaxy clusters and in the field. The aim is to determine the accuracy and robustness of constraints that can be obtained...
Modeling the accretion history of supermassive black holes (2004)
There is overwhelming evidence for the presence of supermassive black holes (SMBHs) in the centers of most nearby galaxies. The mass estimates for these remnant black holes from the stellar...
Limousin, Marceau, Kneib, Jean Paul, Natarajan, Priyamvada
We present a maximum-likelihood analysis of galaxy-galaxy lensing effects in galaxy clusters and in the field. The aim is to determine the accuracy and robustness of constraints that can be obtained...
Limousin, Marceau, Kneib, Jean Paul, Natarajan, Priyamvada
We present a maximum-likelihood analysis of galaxy-galaxy lensing effects in galaxy clusters and in the field. The aim is to determine the accuracy and robustness of constraints that can be obtained...
Natarajan, Priyamvada, Loeb, Abraham, Kneib, Jean-Paul, Smail, Ian
The detailed distribution of mass within clusters of galaxies can be used to probe the nature of dark matter. We show that constraints on the extent of the mass distribution around galaxies in the...
Evidence for tidal stripping of dark matter halos in massive cluster-lenses (2002)
Natarajan, Priyamvada, Kneib, Jean-Paul, Smail, Ian
In this letter, we present the results of our study of galaxy-galaxy lensing in massive cluster-lenses spanning $z = 0.17$ to 0.58, utilizing high-quality archival {\it Hubble Space Telescope} ({\it...
The afterglow and complex environment of the optically dim burst GRB 980613 (2002)
Hjorth, Jens, Thomsen, Bjarne, Nielsen, Svend R., Andersen, Michael I., Holland, Stephen T., Fynbo, Johan U., ...
We report the identification of the optical afterglow of GRB 980613 in R- and I-band images obtained between 16 and 48 hours after the gamma-ray burst. Early near-infrared (NIR) H and K' observations...
Accretion during the merger of supermassive black holes (2002)
Armitage, Philip J., Natarajan, Priyamvada
We study the evolution of disk accretion during the merger of supermassive black hole binaries in galactic nuclei. In hierarchical galaxy formation models, the most common binaries are likely to...
Probing the mass distribution in groups of galaxies using gravitational lensing (2001)
Moller, Ole, Natarajan, Priyamvada, Kneib, Jean-Paul, Blain, Andrew
In this paper, we study gravitational lensing by groups of galaxies. Since groups are abundant and therefore have a large covering fraction on the sky, lensing by groups is likely to be very...
Do angular momentum induced ellipticity correlations contaminate weak lensing measurements? (2001)
Natarajan, Priyamvada, Crittenden, Robert G., Pen, Ue-Li, Theuns, Tom
Alignments in the angular momentum vectors of galaxies can induce large scale correlations in their projected orientations. Such alignments arise from the tidal torques exerted on neighboring...
Crittenden, Robert G., Natarajan, Priyamvada, Pen, Ue-Li, Theuns, Tom
The distortion field defined by the ellipticities of galaxy shapes projected on the sky can be uniquely decomposed into a gradient and a curl component. If the observed ellipticities are induced by...
Spin induced galaxy alignments and their implications for weak lensing measurements (2000)
Crittenden, Robert G., Natarajan, Priyamvada, Pen, Ue-Li, Theuns, Tom
Large scale correlations in the orientations of galaxies can result from alignments in their angular momentum vectors. These alignments arise from the tidal torques exerted on neighboring...
Stellar contributors to the hard X-ray background? (2000)
Natarajan, Priyamvada, Almaini, Omar
We use simple energetic arguments to estimate the contribution of massive X-ray binaries and supernova remnants to the cosmic X-ray background (XRB) at energies in excess of 2 keV. Recent surveys...
Natarajan, Priyamvada, Refregier, Alexandre
We propose a new technique to directly measure the shapes of dark matter halos of galaxies using weak gravitational lensing. Extending the standard galaxy-galaxy lensing method, we show that the...
Gamma-ray bursts and the history of star formation (1999)
Blain, Andrew W., Natarajan, Priyamvada
Popular models for the origin of gamma-ray bursts (GRBs) include short-lived massive stars as the progenitors of the fireballs. Hence the redshift distribution of GRBs should track the cosmic star...
Galaxy-galaxy lensing in clusters: new results (1999)
Natarajan, Priyamvada, Kneib, Jean-Paul, Smail, Ian
A synopsis of the recent results from our study of galaxy-galaxy lensing in clusters is presented. We have applied our analysis techniques to the sample of HST cluster-lenses that span a redshift...
Lensing by Groups of Galaxies (1999)
Moeller, Ole, Natarajan, Priyamvada
A large fraction of known galaxy-lens systems require a component of external shear to explain the observed image geometries. In most cases, this shear can be attributed to a nearby group of...
The Blandford-Znajek mechanism and emission from isolated accreting black holes (1999)
Armitage, Philip J., Natarajan, Priyamvada
In the presence of a magnetic field, rotational energy can be extracted from black holes via the Blandford-Znajek mechanism. We use self-similar advection dominated accretion (ADAF) models to...
Lense-Thirring precession of accretion disks around compact objects (1999)
Armitage, Philip J., Natarajan, Priyamvada
Misaligned accretion disks surrounding rotating compact objects experience a torque due to the Lense-Thirring effect, which leads to precession of the inner disk. It has been suggested that this...
Consequences of feedback from early supernovae for disk assembly (1998)
In this letter we examine the role of the first supernovae in proto-galaxies, their role in feedback and the consequences for disk assembly. Extending the picture proposed by Dekel & Silk (1986), we...
Warped discs and the directional stability of jets in Active Galactic Nuclei (1998)
Natarajan, Priyamvada, Armitage, Philip J.
Warped accretion discs in Active Galactic Nuclei (AGN) exert a torque on the black hole that tends to align the rotation axis with the angular momentum of the outer disc. We compute the magnitude of...
Accretion history of super-massive black holes (1998)
We show that the luminosity function of the actively star-forming Lyman break galaxies and the B-band quasar luminosity function at $z = 3$ can be fit reasonably well with the mass function of...
The alignment of disk and black hole spins in active galactic nuclei (1998)
Natarajan, Priyamvada, Pringle, J. E.
The inner parts of an accretion disk around a spinning black hole are forced to align with the spin of the hole by the Bardeen-Petterson effect. Assuming that any jet produced by such a system is...
High-redshift galaxies, their active nuclei and central black holes (1997)
Haehnelt, Martin G., Natarajan, Priyamvada, Rees, Martin J.
We demonstrate that the luminosity function of the recently detected population of star-forming galaxies and the QSO luminosity function at z=3 can be matched with the mass function of dark matter...
Do cluster galaxies have extended dark halos? (1997)
We present the results of the application of the methodology introduced by Natarajan & Kneib (1997) to interpret local perturbations to the cluster shear field resulting from mass associated with...
Quasar outflows and the formation of dwarf galaxies (1997)
Natarajan, Priyamvada, Sigurdsson, Steinn, Silk, Joseph
We propose a scenario for the formation of a population of baryon-rich, dark matter-deficient dwarf galaxies at high redshift that form from the mass swept out in the Intergalactic Medium (IGM) by...
Estimating the mass density of neutral gas at $z < 1$ (1997)
Natarajan, Priyamvada, Pettini, Max
We use the relationships between galactic HI mass and B-band luminosity determined by Rao & Briggs to recalculate the mass density of neutral gas at the present epoch based on more recent measures of...
Gamma-ray bursts from stellar remnants: probing the Universe at high redshift (1997)
Bloom, Joshua S., Bagla, Jasjeet S., Natarajan, Priyamvada
A gamma-ray burst (GRB) releases an amount of energy similar to that of a supernova explosion, which combined with its rapid variability suggests an origin related to neutron stars or black holes....
Natarajan, Priyamvada, Kneib, Jean-Paul, Smail, Ian, Ellis, Richard S.
We present a new wide field image of the distant cluster AC114 ($z=0.31$) obtained with Wide Field and Planetary Camera II onboard the Hubble Space Telescope. This image considerably extends our...
Sunyaev-Zeldovich decrements with no clusters? (1997)
Natarajan, Priyamvada, Sigurdsson, Steinn
Sunyaev-Zeldovich decrements in the temperature of the Cosmic Microwave Background (CMB) are produced by Thomson scattering of the CMB photons by the confined hot electrons in the Intra-Cluster...
Distribution functions for clusters of galaxies from N-body simulations (1996)
Natarajan, Priyamvada, Hjorth, Jens, Van Kampen, Eelco
We present the results of an attempt to adapt the distribution function formalism to characterize large-scale structures like clusters of galaxies that form in a cosmological N-body simulation. While...
Lensing by galaxy halos in clusters of galaxies (1996)
Natarajan, Priyamvada, Kneib, Jean-Paul
Weak shear maps of the outer regions of clusters have been successfully used to map the distribution of mass at large radii from the cluster center. The typical smoothing lengths employed thus far...
An analytic approximation to the isothermal sphere (1996)
Natarajan, Priyamvada, Lynden-Bell, Donald
We present a useful analytic approximation to the solution of the Lane-Emden equation for infinite polytropic index - the isothermal sphere. The optimized expression obtained for the density profile...
Probing the dynamics of cluster-lenses (1996)
Natarajan, Priyamvada, Kneib, Jean-Paul
We propose a new approach to study the dynamical implications of mass models of clusters for the velocity structure of galaxies in the core. Strong and weak lensing data are used to construct the...
Effect of Sub-Structure in Clusters on the Local Weak-Shear Field (1995)
Natarajan, Priyamvada, Kneib, Jean-Paul
Weak shear maps of the outer regions of clusters have been successfully used to map the distribution of mass at large radii. The effects of substructure in clusters on such reconstructions of the...
Study of the dynamics of the core of A2218 (1995)
We report the results of an attempt to study the velocity structure of the core of the cluster A2218 in order to probe its dynamical state. The aim is to understand if the core is indeed virialized?...
Berry's phase and the Jahn-Teller system /--by Priyamvada Natarajan. (1990)
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Physics, 1991.
The effective potential at finite temperature /--by Priyamvada Natarajan. (1990)
Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Physics, 1990.