Puragra Guhathakurta

The SPLASH Survey: Internal Kinematics, Chemical Abundances, and Masses of the Andromeda I, II, III, VII, X, and XIV dSphs (2009)

Kalirai, Jason S., Beaton, Rachael L., Geha, Marla C., Gilbert, Karoline M., Guhathakurta, Puragra, Kirby, Evan N., ...

We present new Keck/DEIMOS spectroscopic observations of hundreds of individual stars along the sightline to Andromeda's first three discovered dwarf spheroidal galaxies (dSphs) - And I, II, and III,...

The Splash Survey: A Spectroscopic Portrait of Andromeda's Giant Southern Stream (2009)

Gilbert, Karoline M., Guhathakurta, Puragra, Kollipara, Priya, Beaton, Rachael L., Geha, Marla C., Kalirai, Jason S., ...

The giant southern stream (GSS) is the most prominent tidal debris feature in M31's stellar halo and covers a significant fraction of its southern quadrant. The GSS is a complex structure composed of...

The SPLASH Survey: A Spectroscopic Portrait of Andromeda's Giant Southern Stream (2009)

Gilbert, Karoline M., Guhathakurta, Puragra, Kollipara, Priya, Beaton, Rachael L., Geha, Marla C., Kalirai, Jason S., ...

The giant southern stream (GSS) is the most prominent tidal debris feature in M31's stellar halo. The GSS is composed of a relatively metal-rich, high surface-brightness "core" and a lower...

The SPLASH Survey: A Spectroscopic Analysis of the Metal-Poor, Low-Luminosity M31 dSph Satellite Andromeda X (2009)

Kalirai, Jason S., Zucker, Daniel B., Guhathakurta, Puragra, Geha, Marla, Kniazev, Alexei Y., Martinez-Delgado, David, ...

Andromeda X (And X) is a newly discovered low-luminosity M31 dwarf spheroidal galaxy (dSph) found by Zucker et al. (2007) in the Sloan Digital Sky Survey (SDSS - York et al. 2000). In this paper, we...

Multi-Element Abundance Measurements from Medium-Resolution Spectra. I. The Sculptor Dwarf Spheroidal Galaxy (2009)

Kirby, Evan N., Guhathakurta, Puragra, Bolte, Michael, Sneden, Christopher, Geha, Marla C.

We present measurements of Fe, Mg, Si, Ca, and Ti abundances for 388 radial velocity member stars in the Sculptor dwarf spheroidal galaxy (dSph), a satellite of the Milky Way. This is the largest...

The Dominance of Metal-Rich Streams in Stellar Halos: A Comparison Between Substructure in M31 and Lambda-CDM Models (2009)

Gilbert, Karoline M., Font, Andreea S., Johnston, Kathryn V., Guhathakurta, Puragra

Extensive photometric and spectroscopic surveys of the Andromeda galaxy (M31) have discovered tidal debris features throughout M31's stellar halo. We present stellar kinematics and metallicities in...

Deep Optical Photometry of Six Fields in the Andromeda Galaxy (2009)

Brown, Thomas M., Smith, Ed, Ferguson, Henry C., Guhathakurta, Puragra, Kalirai, Jason S., Kimble, Randy A., ...

Using the Advanced Camera for Surveys on the Hubble Space Telescope, we have obtained deep optical images reaching well below the oldest main sequence turnoff in six fields of the Andromeda Galaxy....

A Survey of UV Bright Sources Behind the Halo of M31 (2009)

Fittingoff, Andrew, Prochaska, J. Xavier, Kalirai, Jasonjot S., Strader, Jay, Guhathakurta, Puragra, Kaplan, Kyle F.

We have performed a wide-area ultraviolet (UV) imaging survey using the GALaxy Evolution eXplorer (GALEX) to search for bright, point-like UV sources behind M31's extended halo. Our survey consisted...

"An Era of Precision Astrophysics: Connecting Stars, Galaxies and the Universe," an Astro2010 Science White Paper (2009)

Olling, Rob P., Allen, Ron J., Anderson, Jay, Chaboyer, Brian C., Freedman, Wendy, Guhathakurta, Puragra, ...

Abridged: The golden age of astrophysics is upon us with both grand discoveries (extra-solar planets, dark matter, dark energy) and precision cosmology. Fundamental understanding of the working of...

Properties of Dark Matter Revealed by Astrometric Measurements of the Milky Way and Local Galaxies (2009)

Shaya, Edward, Olling, Robert, Ricotti, Massimo, Vogel, Stuart, Majewski, Steven R., Patterson, Richard J., ...

The fact that dark matter (DM), thus far, has revealed itself only on scales of galaxies and larger, again thrusts onto astrophysics the opportunity and the responsibility to confront the age old...

Galactic Dynamics and Local Dark Matter (2009)

Majewski, Steven R., Bullock, James, Burkert, Andreas, Gibson, Brad, Grebel, Eva, Gnedin, Oleg Y., ...

The concordance Lambda Cold Dark Matter (Lambda-CDM) model for the formation of structure in the Universe, while remarkably successful at describing observations of structure on large scales,...

The Role of Dwarf Galaxies in Building Large Stellar Halos (2009)

Kirby, Evan N., Guhathakurta, Puragra, Bullock, James S., Frebel, Anna, Geha, Marla, Gilbert, Karoline M., ...

The hierarchical theory of galaxy formation rests on the idea that smaller galactic structures merge to form the galaxies that we see today. The past decade has provided remarkable observational...

Uncovering extremely metal-poor stars in the Milky Way's ultrafaint dwarf spheroidal satellite galaxies (2008)

Kirby, Evan N., Simon, Joshua D., Geha, Marla, Guhathakurta, Puragra, Frebel, Anna

We present new metallicity measurements for 298 individual red giant branch stars in eight of the least luminous dwarf spheroidal galaxies (dSphs) in the Milky Way (MW) system. Our technique is based...

The Extended Star Formation History of the Andromeda Spheroid at 35 Kpc on the Minor Axis (2008)

Brown, Thomas M., Beaton, Rachael, Chiba, Masashi, Ferguson, Henry C., Gilbert, Karoline M., Guhathakurta, Puragra, ...

Using the HST ACS, we have obtained deep optical images reaching well below the oldest main sequence turnoff in fields on the southeast minor-axis of the Andromeda Galaxy, 35 kpc from the nucleus....

Observations of the Gas Reservoir around a Star Forming Galaxy in the Early Universe (2008)

Frye, Brenda L., Bowen, David. V., Hurley, Mairead, Tripp, Todd M., Fan, Xiaohui, Holden, Bradley, ...

We present a high signal-to-noise spectrum of a bright galaxy at z = 4.9 in 14 h of integration on VLT FORS2. This galaxy is extremely bright, i_850 = 23.10 +/- 0.01, and is strongly-lensed by the...

Uncovering Extremely Metal-Poor Stars in the Milky Way's Ultra-Faint Dwarf Spheroidal Satellite Galaxies (2008)

Kirby, Evan N., Simon, Joshua D., Geha, Marla, Guhathakurta, Puragra, Frebel, Anna

We present new metallicity measurements for 298 individual red giant branch stars in eight of the least luminous dwarf spheroidal galaxies (dSphs) in the Milky Way (MW) system. Our technique is based...

The DEEP2 Redshift Survey: Lyman Alpha Emitters in the Spectroscopic Database (2008)

Sawicki, Marcin, Lemaux, Brian C., Guhathakurta, Puragra, Kirby, Evan N., Konidaris, Nicholas P., Martin, Crystal L., ...

We present the first results of a search for Lyman-alpha emitters (LAEs) in the DEEP2 spectroscopic database that uses a search technique that is different from but complementary to traditional...

Metallicity and Alpha-Element Abundance Measurement in Red Giant Stars from Medium Resolution Spectra (2008)

Kirby, Evan N., Guhathakurta, Puragra, Sneden, Christopher

We present a technique that applies spectral synthesis to medium resolution spectroscopy (MRS, R ~ 6000) in the red (6300 A < lambda < 9100 A) to measure [Fe/H] and [alpha/Fe] of individual red giant...

Was the Andromeda Stream Produced by a Disk Galaxy? (2008)

Fardal, Mark A., Babul, Arif, Guhathakurta, Puragra, Gilbert, Karoline M., Dodge, Cara

The halo region of M31 exhibits a startling level of stellar inhomogeneities, the most prominent of which is the "giant southern stream". Our previous analysis indicates that this stream, as well as...

Probing The Cores Of Dense Globular Clusters With The Hubble Space Telescope (2007)

Puragra Guhathakurta

this paper, I draw on results from recent and ongoing studies of the "post core collapse" clusters M15 [NGC 7078] (Yanny et al. 1994a; Guhathakurta et al. 1996, 1997b), M30 [NGC 7099]...

The Luminosity-Linewidth Relation As A Probe Of The Evolution Of Field Galaxies (2007)

Puragra Guhathakurta, Kristine Ing, Matthew Colless, Ted Williams

of evolution of the overall luminosity function, they do not constrain evolution in individual galaxies. We are carrying out a series of observations as part of a long-term program aimed at a better...

Accepted by the Astronomical Journal Tests of the Tully-Fisher Relation I: Scatter in Infrared Magnitude vs 21 cm Width (2007)

Gary M. Bernstein, Puragra Guhathakurta, Somak Raychaudhury, Riccardo Giovanelli, Martha P. Haynes, Terry Herter, ...

We examine the precision of the Tully-Fisher relation (TFR) using a sample of galaxies in the Coma region of the sky, and find that it is good to 5 % or better in measuring relative distances. Total...

Tests of the Tully-Fisher Relation II: Scatter Using Optical Rotation Curves (2007)

Somak Raychaudhury, Kaspar Von Braun, Gary M. Bernstein, Puragra Guhathakurta

We investigate the amount of scatter in the Tully-Fisher relation (TFR) when using optical long-slit Hff rotation curves to determine the velocity widths of spiral galaxies. We study a sample of 25...

Supernovae in Low-Redshift Galaxy Clusters: Observations by the Wise Observatory Optical Transient Search (WOOTS) (2007)

Gal-Yam, Avishay, Maoz, Dan, Guhathakurta, Puragra, Filippenko, Alexei V.

We describe the Wise Observatory Optical Transient Search (WOOTS), a survey for supernovae (SNe) and other variable and transient objects in the fields of redshift 0.06-0.2 Abell galaxy clusters. We...

M31 Transverse Velocity and Local Group Mass from Satellite Kinematics (2007)

Van Der Marel, Roeland P., Guhathakurta, Puragra

We present several different statistical methods to determine the transverse velocity vector of M31. The underlying assumptions are that the M31 satellites on average follow the motion of M31 through...

The Stellar Content of Galaxy Halos: A Comparison between LambdaCDM Models and Observations of M31 (2007)

Font, Andreea S., Johnston, Kathryn V., Ferguson, Annette M. N., Bullock, James S., Robertson, Brant E., Tumlinson, Jason, ...

Recent observations have revealed that high surface-brightness, metal-rich debris is present over large regions of the Andromeda (M31) stellar halo. We use a set of numerical models to determine...

The DEEP2 Galaxy Redshift Survey: The Role of Galaxy Environment in the Cosmic Star-Formation History (2007)

Cooper, Michael C., Newman, Jeffrey A., Weiner, Benjamin J., Yan, Renbin, Willmer, Christopher N. A., Bundy, Kevin, ...

Using galaxy samples drawn from the Sloan Digital Sky Survey and the DEEP2 Galaxy Redshift Survey, we study the relationship between star formation and environment at z ~ 0.1 and z ~ 1. We estimate...

A Subaru/Suprime-Cam Survey of M31's spheroid along the South-East minor axis (2007)

Tanaka, Mikito, Chiba, Masashi, Komiyama, Yutaka, Iye, Masanori, Guhathakurta, Puragra

We have used Suprime-Cam on the Subaru Telescope to conduct a V- and I-band imaging survey of fields sampling the spheroid of the Andromeda galaxy along its south-east minor axis. Our photometric...

Unveiling the Boxy Bulge and Bar of the Andromeda Spiral Galaxy (2007)

Beaton, Rachael L., Majewski, Steven R., Guhathakurta, Puragra, Skrutskie, Michael F., Cutri, Roc M., Good, John, ...

A new, 2.8 deg^2 J, H, Ks near-infrared (NIR) survey from the 2MASS 6X program across the extent of the optical disk of the Andromeda (M31) galaxy provides a clear view of the M31 center almost...

Stellar Kinematics in the Complicated Inner Spheroid of M31: Discovery of Substructure Along the Southeastern Minor Axis and its Relationship to the Giant Southern Stream (2007)

Gilbert, Karoline M., Fardal, Mark, Kalirai, Jasonjot S., Guhathakurta, Puragra, Geha, Marla C., Isler, Jedidah, ...

We present the discovery of a kinematically-cold stellar population along the SE minor axis of the Andromeda galaxy (M31) that is likely the forward continuation of M31's giant southern stream. This...

Discovery of Andromeda XIV: A Dwarf Spheroidal Dynamical Rogue in the Local Group? (2007)

Majewski, Steven R., Beaton, Rachael L., Patterson, Richard J., Kalirai, Jasonjot S., Geha, Marla C., Muñoz, Ricardo R., ...

In the course of our survey of the outer halo of the Andromeda Galaxy we have discovered a remote, possible satellite of that system at a projected 162 kpc (11.7 degrees) radius. The fairly elongated...

The Extended Star Formation History of the Andromeda Spheroid at Twenty One Kiloparsecs on the Minor Axis (2007)

Brown, Thomas M., Smith, Ed, Ferguson, Henry C., Guhathakurta, Puragra, Kalirai, Jasonjot S., Rich, R. Michael, ...

Using the HST ACS, we have obtained deep optical images of a southeast minor-axis field in the Andromeda Galaxy, 21 kpc from the nucleus. In both star counts and metallicity, this field represents a...

The all-wavelength extended groth strip international survey (AEGIS) data sets (2007)

Davis, Michael A., Guhathakurta, Puragra, Konidaris, Nick P., Newman, Jeffrey A., Ashby, Matthew L. N., Biggs, Andrew D., ...

In this the first of a series of Letters, we present a panchromatic data set in the Extended Groth Strip region of the sky. Our survey, the All-Wavelength Extended Groth Strip International Survey...

The DEEP2 galaxy redshift survey: the evolution of the blue fraction in groups and the field (2007)

Gerke, Brian F., Newman, Jeffrey A., Faber, S. M., Cooper, MIchael C., Croton, Darren J., Davis, Marc, ...

We explore the behaviour of the blue galaxy fraction over the redshift range 0.75 ≤z≤ 1.3 in the DEEP2 Survey, both for field galaxies and for galaxies in groups. The primary aim is to...

The DEEP2 galaxy redshift survey: evolution of the colour-density relation at 0.4 less than z less than 1.35 (2007)

Cooper, Michael C., Newman, Jeffery A., Coil, Alison L., Croton, Darren J., Gerke, Brian F., Yan, Renbin, ...

Using a sample of 19 464 galaxies drawn from the DEEP2 Galaxy Redshift Survey, we study the relationship between galaxy colour and environment at 0.4 < z < 1.35 . We find that the fraction of...

Evolution in the halo masses of isolated galaxies between z similar to 1 and z similar to 0: from DEEP2 to SDSS (2007)

Conroy, Charlie, Prada, Francisco, Newman, Jeffrey A., Croton, Darren, Coil, Alison L., Conselice, Christopher J., ...

We measure the evolution in the virial mass-to-light ratio (M 200/LB) and virial-to-stellar mass ratio (M 200/M*) for isolated ∼L* galaxies between z ∼ 1 and z ∼ 0 by combining data...

Tracing the dynamical history of the globular cluster 47 Tucanae (2006)

Monkman, Eric, Sills, Alison, Howell, Justin, Guhathakurta, Puragra, De Angeli, Francesca, Beccari, Giacomo

We use two stellar populations in the globular cluster 47 Tucanae to trace its dynamical history: blue stragglers and low-mass main-sequence stars. We assumed that the blue stragglers were formed...

Supernovae in Low-Redshift Galaxy Clusters: the Type-Ia Supernova Rate (2006)

Sharon, Keren, Gal-Yam, Avishay, Maoz, Dan, Filippenko, Alexei V., GuhaThakurta, Puragra

Supernova (SN) rates are a potentially powerful diagnostic of star formation history (SFH), metal enrichment, and SN physics, particularly in galaxy clusters with their deep, metal-retaining...

The DEEP2 Galaxy Redshift Survey: AEGIS Observations of a Dual AGN at z=0.7 (2006)

Gerke, Brian F., Newman, Jeffrey A., Lotz, Jennifer, Yan, Renbin, Barmby, P., Coil, Alison L., ...

We present evidence for a dual Active Galactic Nucleus (AGN) within an early-type galaxy at z=0.709 in the Extended Groth Strip. The galaxy lies on the red sequence, with absolute magnitude M_B=-21.0...

The Detailed Star Formation History in the Spheroid, Outer Disk, and Tidal Stream of the Andromeda Galaxy (2006)

Brown, Thomas M., Smith, Ed, Ferguson, Henry C., Rich, R. Michael, Guhathakurta, Puragra, Renzini, Alvio, ...

Using the Advanced Camera for Surveys on the Hubble Space Telescope, we have obtained deep optical images reaching stars well below the oldest main sequence turnoff in the spheroid, tidal stream, and...

The DEEP2 Galaxy Redshift Survey: Evolution of the Color-Density Relation at 0.4 < z < 1.35 (2006)

Cooper, Michael C., Newman, Jeffrey A., Coil, Alison L., Croton, Darren J., Gerke, Brian F., Yan, Renbin, ...

Using a sample of 19,464 galaxies drawn from the DEEP2 Galaxy Redshift Survey, we study the relationship between galaxy color and environment at 0.4 < z < 1.35. We find that the fraction of galaxies...

AEGIS: Enhancement of Dust-enshrouded Star Formation in Close Galaxy Pairs and Merging Galaxies up to z ~ 1 (2006)

Lin, Lihwai, Koo, David C., Weiner, Benjamin J., Chiueh, Tzihong, Coil, Alison L., Lotz, Jennifer, ...

Using data from the DEEP2 Galaxy Redshift Survey and HST/ACS imaging in the Extended Groth Strip, we select nearly 100 interacting galaxy systems including kinematic close pairs and morphologically...

Evolution in the Halo Masses of Isolated Galaxies between z~1 and z~0: From DEEP2 to SDSS (2006)

Conroy, Charlie, Prada, Francisco, Newman, Jeffrey A., Croton, Darren, Coil, Alison L., Conselice, Christopher J., ...

We measure the evolution in the virial mass-to-light ratio (M_{200}/L_B) and virial-to-stellar mass ratio (M_{200}/M_\ast) for isolated ~ L* galaxies between z~1 and z~0 by combining data from the...

Tracing the Dynamical History of the Globular Cluster 47 Tucanae (2006)

Monkman, Eric, Sills, Alison, Howell, Justin, Guhathakurta, Puragra, De Angeli, Francesca, Beccari, Giacomo

We use two stellar populations in the globular cluster 47 Tucanae to trace its dynamical history: blue stragglers and low mass main sequence stars. We assumed that the blue stragglers were formed...

Unveiling the Boxy Bulge and Bar of the Andromeda Spiral Galaxy (2006)

Beaton, Rachael L., Majewski, Steven R., Guhathakurta, Puragra, Skrutskie, Michael F., Cutri, Roc M., Good, John, ...

A new, 2.8 deg^2 J,H,K_s infrared survey from the 2MASS 6x program across the extent of the optical disk of the Andromeda (M31) galaxy provides a clear view of the M31 center almost completely...

Unveiling the Boxy Bulge and Bar of the Andromeda Spiral Galaxy (2006)

Beaton, Rachael L., Majewski, Steven R., Guhathakurta, Puragra, Skrutskie, Michael F., Cutri, Roc M., Good, John, ...

A new, 2.8 deg^2 J,H,K_s infrared survey from the 2MASS 6x program across the extent of the optical disk of the Andromeda (M31) galaxy provides a clear view of the M31 center almost completely...

A New Method for Isolating M31 Red Giant Stars: The Discovery of Stars out to a Radial Distance of 165 Kiloparsecs (2006)

Gilbert, Karoline M., Guhathakurta, Puragra, Kalirai, Jasonjot S., Rich, R. Michael, Majewski, Steven R., Ostheimer, James C., ...

We present a method for isolating a clean sample of red giant stars in the outerregions of the Andromeda spiral galaxy (M31) from an ongoing spectroscopic survey using the DEIMOS instrument on the...

The DEEP2 Galaxy Redshift Survey: The Relationship Between Galaxy Properties and Environment at z ~ 1 (2006)

Cooper, Michael C., Newman, Jeffrey A., Croton, Darren J., Weiner, Benjamin J., Willmer, Christopher N. A., Gerke, Brian F., ...

We study the mean environment of galaxies in the DEEP2 Galaxy Redshift Survey as a function of rest-frame color, luminosity, and [OII] equivalent width. The local galaxy overdensity for >14,000...

Unveiling the Boxy Bulge and Bar of the Andromeda Spiral Galaxy (2006)

Beaton, Rachael L., Majewski, Steven R., Guhathakurta, Puragra, Skrutskie, Michael F., Cutri, Roc M., Good, John, ...

A new, 2.8 deg^2 J,H,K_s infrared survey from the 2MASS 6x program across the extent of the optical disk of the Andromeda (M31) galaxy provides a clear view of the M31 center almost completely...

Unveiling the Boxy Bulge and Bar of the Andromeda Spiral Galaxy (2006)

Beaton, Rachael L., Majewski, Steven R., Guhathakurta, Puragra, Skrutskie, Michael F., Cutri, Roc M., Good, John, ...

A new, 2.8 deg^2 J,H,K_s infrared survey from the 2MASS 6x program across the extent of the optical disk of the Andromeda (M31) galaxy provides a clear view of the M31 center almost completely...

The DEEP2 Galaxy Redshift Survey: the relationship between galaxy properties and environment at z similar to 1 (2006)

Cooper, Michael C., Newman, Jeffrey A., Croton, Darren J., Weiner, Benjamin J., Willmer, Christopher N. A., Gerke, Brian F., ...

We study the mean environment of galaxies in the DEEP2 Galaxy Redshift Survey as a function of rest-frame colour, luminosity, and [O ii] 3727 Å equivalent width. The local galaxy overdensity...

Deep Photometry of Andromeda Reveals Striking Similarities in the Tidal Stream and Spheroid Populations (2005)

Brown, Thomas M., Smith, Ed, Guhathakurta, Puragra, Rich, R. Michael, Ferguson, Henry C., Renzini, Alvio, ...

We present a color-magnitude diagram (CMD) for a field in the giant tidal stream of the Andromeda galaxy (M31). These observations, taken with the Advanced Camera for Surveys on the Hubble Space...

The DEEP2 Galaxy Redshift Survey: Discovery of Luminous, Metal-poor, Sta r-forming Galaxies at Redshifts z~0.7 (2005)

Hoyos, Carlos, Koo, David C., Phillips, Andrew C., Willmer, Christopher N. A., Guhathakurta, Puragra

We have discovered a sample of 17 metal-poor, yet luminous, star-forming galaxies at redshifts z~0.7. They were selected from the initial phase of the DEEP2 survey of 3900 galaxies and the Team Keck...

The DEEP2 Galaxy Redshift Survey: Clustering of Groups and Group Galaxies at z~1 (2005)

Coil, Alison L., Gerke, Brian F., Newman, Jeffrey A., Ma, Chung-Pei, Yan, Renbin, Cooper, Michael C., ...

We study the clustering properties of groups and of galaxies in groups in the DEEP2 Galaxy Redshift Survey dataset at z~1. Four clustering measures are presented: 1) the group correlation function...

Stellar Cluster Fiducial Sequences with the Advanced Camera for Surveys (2005)

Brown, Thomas M., Ferguson, Henry C., Smith, Ed, Guhathakurta, Puragra, Kimble, Randy A., Sweigart, Allen V., ...

We present color-magnitude diagrams of five Galactic globular clusters and one Galactic open cluster spanning a wide range of metallicity (-2.1 < [Fe/H] < +0.3), as observed in the F606W (broad V)...

Discovery of an extended halo of metal-poor stars in the Andromeda spiral galaxy (2005)

Guhathakurta, Puragra, Ostheimer, James C., Gilbert, Karoline M., Rich, R. Michael, Majewski, Steven R., Kalirai, Jasonjot S., ...

Understanding galaxy formation involves look-back and fossil-record studies of distant and nearby galaxies, respectively. Debris trails in our Galaxy's spheroidal halo of old stars provide evidence...

The Deep2 Galaxy Redshift Survey: Evolution of Close Galaxy Pairs and Major-Merger Rates Up to z ~ 1.2 (2004)

Lin, Lihwai, Koo, David C., Willmer, Christopher N. A., Patton, David R., Conselice, Christopher J., Yan, Renbin, ...

We derive the close, kinematic pair fraction and merger rate up to z ~ 1.2 from the initial data of the DEEP2 Redshift Survey. Assuming a mild luminosity evolution, the number of companions per...

The DEEP2 Galaxy Redshift Survey: First results on galaxy groups (2004)

Gerke, Brian F., Newman, Jeffrey A., Davis, Marc, Marinoni, Christian, Yan, Renbin, Coil, Alison, ...

We use the first 25% of the DEEP2 Galaxy Redshift Survey spectroscopic data to identify groups and clusters of galaxies in redshift space. The data set contains 8370 galaxies with confirmed redshifts...

Detection of the Main Sequence Turn-off of a Newly Discovered Milky Way Halo Structure in the Triangulum-Andromeda Region (2004)

Majewski, Steven R., Ostheimer, James C., Rocha-Pinto, Helio J., Patterson, Richard J., Guhathakurta, Puragra, Reitzel, David

An upper main sequence (MS) and main-sequence turn-off (MSTO) feature appears in the color-magnitude diagram (CMD) of a large area photometric survey of the southern half of M31 stretching to M33....

Dynamics and Stellar Content of the Giant Southern Stream in M31. I. Keck Spectroscopy of Red Giant Stars (2004)

Guhathakurta, Puragra, Rich, R. Michael, Reitzel, David B., Cooper, Michael C., Gilbert, Karoline M., Majewski, Steven R., ...

We present results from a large spectroscopic survey of M31 red giants using the Keck telescope/DEIMOS. Photometric pre-screening, based on the 100A-wide DDO51 band centered on the Mgb/MgH feature,...

Dynamics and Stellar Content of the Giant Southern Stream in M31. II. Interpretation (2004)

Font, Andreea S., Johnston, Kathryn V., Guhathakurta, Puragra, Majewski, Steven R., Rich, R. Michael

We examine the nature of the progenitor of the giant stellar stream in M31 using as constraints new radial velocity measurements of stream red giant stars (presented in the companion paper by...

The Chemical Composition Contrast between M3 and M13 Revisited: New Abundances for 28 Giant Stars in M3 (2003)

Sneden, Christopher, Kraft, Robert P., Guhathakurta, Puragra, Peterson, Ruth C., Fulbright, Jon P.

We report new chemical abundances of 23 bright red giants of the globular cluster M3, based on high-resolution spectra obtained with the Keck I telescope. Combining these data with a...

Keck Spectroscopy of Red Giant Stars in the Vicinity of M31's Massive Globular Cluster G1 (2003)

Reitzel, David B., Guhathakurta, Puragra, Rich, R. Michael

We present results from a Keck spectroscopic survey of red giants in a field near M31's major axis, ~34kpc in projection from the nucleus, near the globular cluster G1. We use multislit LRIS...

Deep Photometry in a Remote M31 Major Axis Field Near G1 (2003)

Rich, R. Michael, Reitzel, David B., Guhathakurta, Puragra, Gebhardt, Karl, Ho, Luis C.

We present photometry from Hubble Space Telescope (HST)/Wide Field Planetary Camera 2 parallel imagery of a remote M31 field at a projected distance of about 34 kpc from the nucleus near the SW major...

The DEEP2 Galaxy Redshift Survey: Clustering of Galaxies in Early Data (2003)

Coil, Alison L., Davis, Marc, Madgwick, Darren S., Newman, Jeffrey A., Conselice, Christopher J., Cooper, Michael, ...

We measure the two-point correlation function xi(r) using a sample of 2219 galaxies in an area of 0.32 degrees^2 at z=0.7-1.35 from the first season of the DEEP2 Galaxy Redshift Survey. We find that...

The DEEP2 Galaxy Redshift Survey: Spectral classification of galaxies at z~1 (2003)

Madgwick, Darren S., Coil, Alison L., Conselice, Christopher J., Cooper, Michael C., Davis, Marc, Ellis, Richard S., ...

We present a Principal Component Analysis (PCA)-based spectral classification, eta, for the first 5600 galaxies observed in the DEEP2 Redshift Survey. This parameter provides a very pronounced...

A Population of Intergalactic Supernovae in Galaxy Clusters (2002)

Gal-Yam, Avishay, Maoz, Dan, Guhathakurta, Puragra, Filippenko, Alexei V.

We have discovered seven type Ia cluster supernovae (SNe) in the course of the Wise Observatory Optical Transients Search in the fields of galaxy clusters with redshifts between z=0.06 and z=0.2. Two...

Addendum: "Hubble Space Telescope Evidence for an Intermediate-Mass Black Hole in the Globular Cluster M15: II. Kinematical Analysis and Dynamical Modeling" (2002)

Gerssen, Joris, Van Der Marel, Roeland P., Gebhardt, Karl, Guhathakurta, Puragra, Peterson, Ruth, Pryor, Carlton

It has been reported that there is an error in the figure in Dull et al. (1997, D97) that shows the radial M/L profile in Fokker-Planck models of M15. We discuss how this modifies the interpretation...

Hubble Space Telescope Evidence for an Intermediate-Mass Black Hole in the Globular Cluster M15: I. STIS Spectroscopy and WFPC2 Photometry (2002)

Van Der Marel, Roeland P., Gerssen, Joris, Guhathakurta, Puragra, Peterson, Ruth, Gebhardt, Karl

In this series of two papers we describe a project with STIS on HST to measure the line-of-sight velocities of stars in the central few arcsec of the dense globular cluster M15. This first paper...

Hubble Space Telescope Evidence for an Intermediate-Mass Black Hole in the Globular Cluster M15: II. Kinematical Analysis and Dynamical Modeling (2002)

Gerssen, Joris, Van Der Marel, Roeland P., Gebhardt, Karl, Guhathakurta, Puragra, Peterson, Ruth, Pryor, Carlton

We analyze HST/STIS spectra (see Paper I) of the central region of the dense globular cluster M15. We infer the velocities of 64 individual stars, two-thirds of which have their velocity measured for...

Metallicity and Kinematics of M31's Outer Stellar Halo from a Keck Spectrocscopic Survey (2002)

Reitzel, David B., Guhathakurta, Puragra

We present multislit CaII near-infrared triplet spectroscopy with the Keck 10-m telescope/LRIS of 99 M31 halo red giant candidates in the apparent mag range 20

Tidal Interaction of M32 and NGC 205 with M31: Surface Photometry and Numerical Simulations (2001)

Choi, Philip I., Guhathakurta, Puragra, Johnston, Kathryn V.

We investigate the interaction history of the M31 sub-group of galaxies by comparing surface photometry of its two nearest satellites, M32 and NGC 205, with N-body simulations of satellite...

Interpreting the Morphology of Diffuse Light Around Satellite Galaxies (2001)

Johnston, Kathryn V., Choi, Philip I., Guhathakurta, Puragra

Recent observations of surface brightness distributions of both Milky Way and M31 satellite galaxies have revealed many instances of sudden changes or breaks in the slope of the surface brightness...

The Impact of Tidal Interactions on Satellite Galaxies: A Study of the M31 Satellites, M32 & NGC 205 (2001)

Choi, Philip I., Guhathakurta, Puragra, Johnston, Kathryn V.

Surface photometry of the M31 satellites M32 and NGC 205 is compared to numerical simulations of satellite destruction to constrain orbital parameters and the interaction history of the M31 subgroup....

The Frequency of Binary Stars in the Core of 47 Tucanae (2001)

Albrow, Michael D., Gilliland, Ronald L., Brown, Timothy M., Edmonds, Peter D., Guhathakurta, Puragra, Sarajedini, Ata

Differential time series photometry has been derived for 46422 main-sequence stars in the core of 47 Tucanae. The observations consisted of near-continuous 160-s exposures alternating between the...

Hubble Space Telescope Photometry of the Dwarf Spheroidal Galaxy ESO 410-G005 (2000)

Karachentsev, Igor D., Sharina, Margarita E., Grebel, Eva K., Dolphin, Andrew E., Geisler, Doug, Guhathakurta, Puragra, ...

We present HST WFPC2 imaging of the nearby low-surface-brightness dwarf spheroidal galaxy ESO 410-G005, which has been resolved into stars for the first time. The resulting color-magnitude diagram...

Resolving the Controversy Over the Core Radius of 47 Tucanae (NGC 104) (2000)

Howell, Justin H., Guhathakurta, Puragra, Gilliland, Ronald L.

This paper investigates the discrepancy between recent measurements of the density profile of the globular cluster 47 Tuc that have used HST data sets. Guhathakurta et al. (1992) used...

Keck Studies of M31's Stellar Halo (2000)

Guhathakurta, Puragra, Reitzel, David B., Grebel, Eva K.

We present Keck 10-meter/LRIS spectra of candidate red giants in the halo of M31, located at a projected radius of R=19kpc on the minor axis. These spectroscopic targets have been selected using a...

Radial Color Gradient and Main Sequence Mass Segregation in M30 (NGC 7099) (1999)

Howell, Justin H., Guhathakurta, Puragra, Tan, Amy

It has long been known that the post-core-collapse globular cluster M30 has a bluer-inward color gradient, and recent work suggests that the central deficiency of bright red giants does not fully...

Breaking the Disk/Halo Degeneracy with Gravitational Lensing (1999)

Maller, Ariyeh H., Simard, Luc, Guhathakurta, Puragra, Hjorth, Jens, Jaunsen, Andreas O., Flores, Ricardo A., ...

The degeneracy between the disk and the dark matter contribution to galaxy rotation curves remains an important uncertainty in our understanding of disk galaxies. Here we discuss a new method for...

Magnitude bias of microlensed sources towards the Large Magellanic Cloud (1999)

Zhao, HongSheng, Graff, David, Guhathakurta, Puragra

There are lines of evidence suggesting that some of the observed microlensing events in the direction of the Large Magellanic Cloud (LMC) are caused by ordinary star lenses as opposed to dark Machos...

An Extremely Lithium-Rich Bright Red Giant in the Globular Cluster M3 (1999)

Kraft, Robert P., Peterson, Ruth C., Guhathakurta, Puragra, Sneden, Christopher, Fulbright, Jon P., Langer, G. Edward

We have serendipitously discovered an extremely lithium-rich star on the red giant branch of the globular cluster M3 (NGC 5272). An echelle spectrum obtained with the Keck I HIRES reveals a Li I 6707...

Extinction Curves, Distances, and Clumpiness of Diffuse Interstellar Dust Clouds (1999)

Szomoru, Arpad, Guhathakurta, Puragra

We present CCD photometry in UBVRI of several thousand Galactic field stars in four large (>1 degree^2) regions centered on diffuse interstellar dust clouds, commonly referred to as ``cirrus'' clouds...

Properties of Two New M31 dSph Companions from Keck Imaging (1998)

Grebel, Eva K., Guhathakurta, Puragra

We have obtained Keck Low Resolution Imaging Spectrograph images in V and I of the newly discovered Local Group dwarf galaxies Pegasus dSph and Cassiopeia dSph and their surrounding field. The first...

Globular Cluster Photometry with the Hubble Space Telescope VII. Color Gradients and Blue Stragglers in the Central Region of M30 (NGC 7099) from WFPC2 Observations (1998)

Guhathakurta, Puragra, Webster, Zodiac T., Yanny, Brian, Schneider, Donald P., Bahcall, John N.

We present F555W (V), F439W (B), and F336W (U) photometry of 9507 stars in the central 2' of the dense, post core collapse cluster M30 (NGC 7099) derived from HST WFPC2 images. These data are used to...

Isolating Red Giant Stars in M31's Elusive Outer Spheroid (1998)

Reitzel, David B., Guhathakurta, Puragra, Gould, Andrew

Deep UBRI images of a 15'x15' field in the M31 galaxy's outer spheroid obtained with the KPNO 4-m telescope, and Keck 10-m telescope+LRIS I-band images, are used to isolate candidate red giant branch...

Deep optical imaging of the bright Seyfert galaxy NGC 5548: a long, very low surface brightness tail (1998)

Tyson, J. Anthony, Fischer, Philippe, Guhathakurta, Puragra, McIlroy, Peter, Wenk, R. A., Huchra, John P., ...

Deep Hubble Space Telescope Wide Field Camera (WFC-1) imaging of a region 3farcm7 east of the V = 13 mag Seyfert galaxy NGC 5548 in the F555W and F785LP bands, and deep ground-based V and I imaging,...

Deep optical imaging of the bright Seyfert galaxy NGC 5548: a long, very low surface brightness tail (1998)

Tyson, J. Anthony, Fischer, Philippe, Guhathakurta, Puragra, McIlroy, Peter, Wenk, R. A., Huchra, John P., ...

Deep Hubble Space Telescope Wide Field Camera (WFC-1) imaging of a region 3farcm7 east of the V = 13 mag Seyfert galaxy NGC 5548 in the F555W and F785LP bands, and deep ground-based V and I imaging,...

Optical Spectroscopy of Galactic Cirrus Clouds: Extended Red Emission in the Diffuse Interstellar Medium (1997)

Szomoru, Arpad, Guhathakurta, Puragra

We present initial results from the first optical spectroscopic survey of high latitude Galactic cirrus clouds. The observed shape of the cirrus spectrum does not agree with that of scattered ambient...

Tests of the Tully-Fisher Relation II: Scatter Using Optical Rotation Curves (1997)

Raychaudhury, Somak, Von Braun, Kaspar, Bernstein, Gary M., Guhathakurta, Puragra

We investigate the amount of scatter in the Tully-Fisher relation (TFR) when using optical long-slit H-alpha rotation curves to determine the velocity widths of spiral galaxies. We study a sample of...

Globular Cluster Photometry with the Hubble Space Telescope. VI. WF/PC-I Observations of the Stellar Populations in the Core of M13 (NGC 6205) (1996)

Cohen, Randi L., Guhathakurta, Puragra, Yanny, Brian, Schneider, Donald P., Bahcall, John N.

To probe the nature of stellar evolution in dense environments, we study the dense core of the globular cluster Messier 13 using pre-refurbishment Planetary Camera-I images obtained with the Hubble...

Globular Cluster Photometry with the Hubble Space Telescope. V. WFPC2 Study of M15's Central Density Cusp (1995)

Guhathakurta, Puragra, Yanny, Brian, Schneider, Donald P., Bahcall, John N.

We describe images of the center of the dense globular cluster M15 (NGC 7078) obtained with the Hubble Space Telescope Wide Field and Planetary Camera 2 (WFPC2). Data taken in the F336W, F439W, and...

A Catalog of Digital Images of 113 Nearby Galaxies (1995)

Frei, Zsolt, Guhathakurta, Puragra, Gunn, James E., Tyson, J. Anthony

We present a digital catalog of images of 113 galaxies in this paper. These galaxies are all nearby, bright, large and well resolved. All images were recorded with charge coupled devices (CCDs) at...

Detection of Lens Candidates for the Double QSO Q2345+007 (1994)

Fischer, Philippe, Tyson, J. Anthony, Bernstein, Gary M., Guhathakurta, Puragra

Luminous objects associated with the 7.06\arcsec\ separation double quasar Q2345+007 have, until now, escaped detection. In this letter we present the results of the deepest known imaging of the...