Search Publications
NGC 2419, M92, and the age gradient in the galactic halo
Bond, Howard E.; Stetson, Peter B.; Richer, Harvey B. +7 more
The WFPC2 camera on HST has been used to obtain photometry of the low-metallicity ([Fe/H] =-2.14), outer-halo globular cluster NGC 2419. Our color-magnitude diagram in (V, V-I) reaches Vlim =~ 27.8, clearly delineating the subgiant and turnoff region and about three magnitudes of the unevolved main sequence. A differential fit of the NG…
WFPC2 Observations of the Carina Dwarf Spheroidal Galaxy.
Mighell, Kenneth J.
We present our analysis of Hubble Space Telescope Wide Field Planetary Camera 2 observations in F555W (∼V) and F814W (∼I) of the Carina dwarf spheroidal galaxy. The resulting V vs V-I color-magnitude diagrams reach V≈27.1 mag. The reddening of Carina is estimated to be E(V-I)=0.08±0.02 mag. A new estimate of the distance modulus of Carina, (m - M)…
HST/GHRS Observations of the Compact Slow Ejecta of Eta Carinae
Humphreys, R. M.; Balick, B.; Davidson, Kris +6 more
We report spectroscopic observations of eta Car and adjacent gas with an unprecedented combination of spatial and spectral resolution, 0.1 arcsec x 0.1 Angstroms. Radial velocities show that the bright objects C and D, 0.2 arcsec from the star, are slow equatorial ejecta. The narrow emission lines which fluctuate in the spectrum of the core region…
HST and Infrared Images of the Circumstellar Environment of the Cool Hypergiant IRC + 10420
Smith, Nathan; Humphreys, Roberta M.; Davidson, Kris +6 more
We present HST WFPC2 and ground-based infrared images of the very evolved, luminous OH/IR star IRC+10420. The HST optical images reveal an amazingly complex environment, with one or more distant reflection shells probably ejected during the star's previous red supergiant stage plus numerous features within two arcseconds of the star including cond…
Hubble Space Telescope Observations of Two Dynamically Young Elliptical Galaxies
Whitmore, Bradley C.; Fall, S. Michael; Miller, Bryan W. +1 more
High-resolution images of the candidate dynamically young ellipticals NGC 1700 and NGC 3610 have been obtained with the WFPC2 of the Hubble Space Telescope. NGC 1700 contains approximately a dozen dust clouds arranged in a chaotic distribution near the center of the galaxy, suggestive of a merger or accretion event. NGC 3610 contains a remarkably …
Stellar Populations in the Dwarf Elliptical Galaxy NGC 147
Krist, J.; Stapelfeldt, K.; Gallagher, J. S., III +16 more
Deep V and I CCD images in a central and an outer field of the Local Group dwarf elliptical galaxy NGC 147 have been obtained with the Wide Field and Planetary Camera-2 (WFPC2) on board of the Hubble Space Telescope. The color-magnitude diagram shows a number of interesting features, including a well defined red giant branch (RGB), a red horizonta…
Stellar Populations in the Large Magellanic Cloud:Evidence for a Significant Number of Older Stars or a Steeper IMF?
Stapelfeldt, K. R.; Clarke, J. T.; Grillmair, Carl J. +14 more
We present deep photometry obtained with the HST in an outer LMC field. A well-defined main sequence is seen down to V>26. We derive a luminosity function from the data and use it to constrain the IMF and the star formation history. We derive limits on the IMF slope, alpha (with dN/dM~ M(alpha ) ), from stars on the main sequence which are fain…
A Comparison of Deep HST Luminosity Functions of Four Globular Clusters
Piotto, Giampaolo; Cool, Adrienne M.; King, Ivan R.
From deep color-magnitude arrays made from V and I images taken with Hubble Space Telescope's WFPC2 camera we have determined luminosity functions (LFs) down to a level that corresponds to ~ 0.13 \msun, for the low-metal-abundance globular clusters M15, M30, M92, and NGC 6397. Because of the similarity of the metallicities of these clusters, diffe…
HST Imagery of the Non-Expanding, Clumped "Shell" of the Recurrent Nova T Pyxidis
Williams, Robert E.; Zurek, David R.; Moffat, Anthony F. J. +3 more
The "shell" of the recurrent nova T Pyxidis has been resolved with HST imagery into more than two thousand individual knots. Hydrogen and [N II] emission have very similar spatial distributions. Four epochs of observation allow us to place an upper limit of 40 km/s on the systematic expansion velocity of the knots. This is in contrast to our 1985 …
The Apparent Morphology of Peculiar Galaxies at Intermediate to High Redshifts
Vacca, W. D.; Hibbard, J. E.
To understand the range of morphologies observed in the galaxy population at high redshift, it is instructive to evaluate the appearance of local peculiar galaxies when placed at cosmological distances. To this end, we use rest-frame ultraviolet (UV), B- and V-band images of five nearby (ζ<0.02) interacting and/or starbursting galaxies to simul…