Puragra (Raja) GuhaThakurta

UCO/Lick Observatory
Department of Astronomy & Astrophysics
University of California Santa Cruz
271 Interdisciplinary Sciences Building
1156 High Street
Santa Cruz, CA 95064
Phone: (831)459-5169
FAX: (831)426-3115
Email: raja@ucolick.org


Astronomy 2: Overview of the Universe (Fall 2013) web page


Current research


Science Internship Program (SIP): Research opportunities in STEM fields at UCSC for high-school students

Click here for the old SIP website.


Art


Media coverage

July 2014 article "High-school scientists/Galactic exploration" (courtesy of International Innovation, Research Media Ltd. - a leading scientific dissemination service) about SIP and the SPLASH collaboration's research highlights
July 2014 article in the Palo Alto Weekly entitled "Stoking a passion for science" featuring SIP.
January 2014 JWST Hangout on Air (AAS meeting, Washington DC), a discussion about galaxy evolution studies and research by high-school students in the SIP program (originally streamed live)
December 2013 article "Getting Girls to Thrive in STEM" in Castilleja School's Full Circle magazine
May 2012 press release about the impending Andromeda-Milky Way collision
December 2011 Google Tech Talk at Google HQ in Mountain View, CA about "Our Place in the Cosmos"
July 2011 article in Science magazine featuring the SPLASH group's work
January 2010 press release on Andromeda tidal streams: UCSC site, Keck Observatory site, National Science Foundation site, and Subaru Telescope site

The SPLASH project and collaboration page
Personal profile (summary of past research interests, mugshot!)

A picture's worth a thousand words...... (older research results)


Interstellar Dust Cloud:

High latitude tenuous clouds of interstellar dust, commonly referred to as "cirrus", reflect ambient starlight. An optical B band image of one such nebula, 1038+83, obtained with the KPNO Burrell Schmidt telescope. We have dubbed it "The Witch" for obvious reasons. Optical spectroscopy of cirrus clouds with the Lick 3-meter telescope and KAST spectrograph reveals evidence of photoluminescence from hydrocarbons.

Dense Star Cluster:

The centers of dense globular clusters are excellent laboratories for studying the effects of stellar interactions. The central density of M15 is among the highest of Galactic globulars. An HST WFPC2 image of the central 9"x9" of M15, color coded to represent intensities in the U, B and V bands, shows that the stellar density rises all the way in to radii less than 0.5" (0.03 pc).

The Great Spiral Galaxy in Andromeda:

The combination of the KPNO Burrell Schmidt telescope and 2048 x 2048 CCDs makes large area surface photometry possible. This system has been used to construct an I band mosaic image of the Andromeda galaxy (M31) covering 4 deg x 3 deg. The central 1 square degree of M31, despite being subsampled 3 x 3 pixels in this display, shows striking dust lanes. The satellite galaxy M32 is to the south, while NGC205 (truncated by the mosaic edge) is to the northwest. The full mosaic of M31 is displayed with 22 x 22 pixel block averaging (left) and median filtering (right). The latter is more efficient at removing foreground stars. Note the gradient in the projected density of foreground stars--the Galactic plane is to the north (up)--and the prominent warp in M31's disk.

Internal Kinematics of Distant Galaxies:

Internal kinematics of faint blue field galaxies can be a valuable probe of their evolutionary history. A z=0.34 field galaxy from our Fabry-Perot study with the CTIO 4-meter telescope shows an O[III] emission line whose width, FWHM = 520 km/s, is significantly broader than the instrumental resolution (left). Further, a spatially resolved kinematical map of this galaxy shows clear evidence for rotation.


.....but, if you prefer to read, here's a selection of papers:


Galaxies, big .....

Kim, Guhathakurta, van Gorkom, Jura & Knapp 1988, "HI Observations of the Elliptical Galaxies NGC2974 and NGC5018", ApJ, 330, 684

Guhathakurta, van Gorkom, Kotanyi & Balkowski 1988, "A VLA HI Survey of the Virgo Cluster Spirals. II. Rotation Curves", AJ, 96, 851

Guhathakurta, Bernstein, Raychaudhury, Haynes, Giovanelli, Herter & Vogt 1993, "The Near-Infrared Tully-Fisher Relation: A Preliminary Study of the Coma and Abell 400 Clusters", PASP, 105, 1022

Bernstein, Guhathakurta, Raychaudhury, Giovanelli, Haynes, Herter & Vogt 1994, "Tests of the Tully-Fisher Relation. I. Scatter in Infrared Magnitude versus 21cm Width", AJ, 107, 1962

Frei, Guhathakurta, Gunn & Tyson 1996, "A Catalog of Digital Images of 113 Nearby Galaxies", AJ, 111, 174

Raychaudhury, von Braun, Bernstein & Guhathakurta 1997, "Tests of the Tully-Fisher Relation. II. Scatter Using Optical Rotation Curves", AJ, 113, 2046

Guhathakurta & Reitzel 1998, "Local Group Suburbia: Red Giants in M31's Outer Spheroid and a Search for Stars in the Magellanic Stream", in Galactic Halos, ed. Zaritsky (ASP Conf Ser, v136), 22

Reitzel, Guhathakurta & Gould 1998, "Isolating Red Giant Stars in M31's Elusive Outer Spheroid", AJ, in press (Aug 98)

..... and small, .....

Weinberg, Szomoru, Guhathakurta & van Gorkom 1991, "On the Population of HI Dwarf Galaxies", ApJL, 372, L13

Gould, Guhathakurta, Richstone & Flynn 1992, "Evidence for Dwarf Stars at D~100kpc Near the Sextans Dwarf Spheroidal Galaxy", ApJ, 388, 345

Szomoru, Guhathakurta, van Gorkom, Knapen, Weinberg & Fruchter 1994, "The Properties of an HI-Selected Galaxy Sample", AJ, 108, 491

....., distant, .....

Guhathakurta, Tyson & Majewski 1990, "A Redshift Limit for the Faint Blue Galaxy Population from Deep U Band Imaging", ApJL, 357, L9

Bahcall, Guhathakurta & Schneider 1990, "What the Longest Exposures from the Hubble Space Telescope Will Reveal", Science, 248, 178

Efstathiou, Bernstein, Katz, Tyson & Guhathakurta 1991, "The Clustering of Faint Galaxies", ApJL, 380, L47

Guhathakurta 1991, "Redshift Constraints and Clustering of Faint Galaxies", in The Early Observable Universe from Diffuse Backgrounds, eds. Rocca-Volmerange et al. (Editions Frontieres), 155

Rix, Guhathakurta, Colless & Ing 1997, "Internal Kinematics of Distant Field Galaxies. I. Emission Linewidths for a Complete Sample of Faint Blue Galaxies at z~0.25", MNRAS, 285, 779

Guhathakurta & Ing 1998, "Evolution and Internal Kinematics of Faint Blue Galaxies", in Highly Redshifted Radio Lines, eds. Carilli et al. (ASP Conf Ser), in press

.....and disturbed

Hibbard, Guhathakurta, van Gorkom & Schweizer 1994, "Cold, Warm, and Hot Gas in the Late-Stage Merger NGC7252", AJ, 107, 67

Tyson, Fischer, Guhathakurta, McIlroy, Wenk, Huchra, Macri, Neuschaefer, Sarajedini, Glazebrook, Ratnatunga & Griffiths 1998, "Deep Optical Imaging of the Bright Seyfert NGC5548: A Long, Very Low Surface Brightness Tail", AJ, in press (July 98)


Dust in our Galaxy.....

Guhathakurta & Draine 1989, "Temperature Fluctuations in Interstellar Grains. I. Computational Method and Evaporation of Small Grains", ApJ, 345, 230

Guhathakurta & Tyson 1989, "Optical Characteristics of Galactic 100 micron Cirrus", ApJ, 346, 773

Guhathakurta & Cutri 1994, "Optical Studies of High Latitude Dust", in The First Symposium on the Infrared Cirrus and Diffuse Interstellar Clouds, eds. Cutri & Latter (ASP Conf Ser, v58), 34

Szomoru & Guhathakurta 1998a, "Optical Spectroscopy of Galactic Cirrus Clouds: Extended Red Emission in the Diffuse Interstellar Medium", ApJL, 494, L93

Szomoru & Guhathakurta 1998b, "Extinction Curves, Distances, and Incident Radiation of Cirrus Clouds", ApJ, in prep

.....and in others

Jura, Kim, Knapp & Guhathakurta 1987, "Interstellar Dust in Shapley-Ames Elliptical Galaxies", ApJL, 312, L11

Knapp, Guhathakurta, Kim & Jura 1989, "IRAS Flux Densities for Early-Type Galaxies", ApJS, 70, 329


Dark matter

Richstone, Gould, Guhathakurta & Flynn 1992, "Constraints on Baryonic Dark Matter in the Galactic Halo and Local Group", ApJ, 388, 354

Guhathakurta 1991, "Gravitational Lensing by Galaxy Clusters", in Clusters & Superclusters of Galaxies, eds. Colless et al. (NATO ASI, Cambridge), 55

Fischer, Tyson, Bernstein & Guhathakurta 1994, "Detection of Lens Candidates for the Double Quasar Q2345+007", ApJL, 431, L71

Guhathakurta 1995, "Faint Blue Galaxies and Gravitational Lensing by Clusters of Galaxies", in Sixth Asian-Pacific Regional Meeting, J Astrophys Astron Sup, 16, 119


HST studies of dense globular clusters

Guhathakurta, Yanny, Schneider & Bahcall 1992, "Globular Cluster Photometry with HST. I. Description of the Method and Analysis of the Core of 47Tuc", AJ, 104, 1790

Yanny, Guhathakurta, Bahcall & Schneider 1994, "Globular Cluster Photometry with HST. II. U, V, and I Measurements of M15", AJ, 107, 1745

Guhathakurta, Yanny, Bahcall & Schneider 1994, "Globular Cluster Photometry with HST. III. Blue Stragglers & Variable Stars in the Core of M3", AJ, 108, 1786

Yanny, Guhathakurta, Schneider & Bahcall 1994, "WFPC2 Observations of the Globular Cluster M30", ApJL, 435, L59

Guhathakurta, Yanny, Schneider & Bahcall 1996, "HST WFPC2 Observations of the Globular Cluster M15. V. The Central Density Cusp", AJ, 111, 267

Edmonds, Gilliland, Guhathakurta, Petro, Saha & Shara 1996, "Stellar Variability in the Central Populations of 47 Tucanae from WF/PC Observations with the Hubble Space Telescope. II. Binary Systems", ApJ, 468, 241

Guhathakurta, Yanny, Schneider & Bahcall 1996, "Hubble Space Telescope Studies of the Dense Central Regions of Globular Clusters", in Dynamical Evolution of Star Clusters, eds. Hut & Makino (Kluwer, Dordrecht), 19

Cohen, Guhathakurta, Yanny, Schneider & Bahcall 1997, "Globular Cluster Photometry with HST. VI. WF/PC-I Observations of the Stellar Populations in the Core of M13", AJ, 113, 669

Guhathakurta, Piotto & Vesperini 1998a, "Mass Functions & Stellar Populations of Globular Clusters", in Highlights of Astronomy v11, ed. Andersen (Kluwer Acad Pub), in press

Guhathakurta, Webster, Yanny, Schneider & Bahcall 1998b, "Globular Cluster Photometry with HST. VII. Color Gradients and Blue Stragglers in the Central Region of M30 (NGC7099) from WFPC2 Observations", AJ, in press (Sept 98)