Search Publications
The M(v)^HB Verses [Fe/H] Calibration. I. HST Color-Magnitude Diagrams of Eight Globular Clusters in M31
Djorgovski, S. G.; Cacciari, C.; Rich, R. M. +6 more
Color magnitude diagrams (CMDs) of individual stars in 8 globular clusters (GCs) in M3 1 down to about 1 mag fainter (V∼26.5) than the horizontal branch (HB) have been obtained with the Hubble Space Telescope-HST. In particular, we observed G280 and G35 1 with the FOC (f/96 + F430W and f/96+F480LP) while the WFPC2 (F555W, F814W) frames for G1, G58…
Intergalactic Hydrogen Clouds OT Low Redshift: Connections to Voids and Dwarf Galaxies
Shull, J. Michael; Stocke, John T.; Penton, Steve
We provide new post-COSTAR data on one sightline (Mrk 421) and updated data from another (I Zw 1) from our Hubble Space Telescope (HST) survey of intergalactic Lyα clouds located along sightlines to four bright quasars passing through well-mapped galaxy voids (16000 km s^-1^ pathlength) and superclusters (18000 km s^-1^) We report two more definit…
The Dwarf Spheroidal Companions to M31: WFPC2 Observations of Andromeda I
Da Costa, G. S.; Armandroff, T. E.; Caldwell, Nelson +1 more
Images have been obtained with the Hubble Space Telescope WFPC2 camera of Andromeda I, a dwarf spheroidal (dSph) galaxy that lies in the outer halo of M31. The resulting color-magnitude diagrams reveal for the first time the morphology of the horizontal branch in this system. We find that, in a similar fashion to many of the galactic dSph companio…
Star Clusters in Interacting and Cooling Flow Galaxies
Watson, A. M.; Holtzman, J. A.; Stapelfeldt, K. R. +13 more
Two interacting galaxies and four central galaxies in cooling flow clusters were observed with the Hubble Space Telescope to look for young compact massive star clusters. The two interacting galaxies, NGC 3597 and NGC 6052, show clear evidence for resolved bright blue clusters that are likely to be comparable in mass to Galactic globulars based on…
Local Group Populations With the Hubble Space Telescope. I. The M31 Globular Cluster G1=Mayall II
Freedman, Wendy L.; Rich, R. Michael; Neill, James D. +1 more
We present WFPC2 photometry of the M31 globular cluster G1 and its adjacent halo field population. The cluster is one of the most luminous in the Local Group (~10^6^ L_sun_) and is at a projected distance of 39.5 kpc from the nucleus near the major axis of M31. The color of the red giant branch is similar to that of 47 Tuc, confirming previous gro…
Double-Peaked Broad Emission Lines in the Nucleus of M81
Heckman, Timothy M.; Bower, Gary A.; Wilson, Andrew S. +1 more
We present recent optical spectroscopy of the nucleus of the spiral galaxy M81 obtained with the post-COSTAR Faint Object Spectrograph (FOS) aboard Hubble Space Telescope (HST). The spectra reveal a new double- peaked broad component in the profiles of Hα and Hβ, the FWZI of which are ~14000 and 11000 km s^-1^, respectively. Such double-peaked bro…
The Leo II Dwarf Spheroidal - an Old Galaxy With a Large Intermediate-age Population
Rich, R. Michael; Mighell, Kenneth J.
Deep F555W (broadband V) and F814W (broadband I) observations have been obtained of the Leo II dwarf spheroidal galaxy with the Hubble Space Telescope Wide Field Planetary Camera 2 instrument. The resulting color- magnitude diagrams reach V = 27.4 mag and I = 26.6 mag, and the fiducial sequence has a main-sequence turnoff at V = 25.1 mag. A metall…
Deep HST V- and I-Band Observations of the Halo of M31: Evidence for Multiple Stellar Populations
Richer, Harvey B.; Fahlman, Gregory G.; Holland, Stephen
We present deep (V~27) V- and I-band stellar photometry obtained using the Hubble Space Telescope's WFPC2 in two fields in the M31 halo. These fields are located 32' and 50' from the center of M31 approximately along the SE minor axis at the locations of the M31 globular star clusters G302 and G3 12, respectively. The M31 halo luminosity functions…
V1974 Cygni 1992: Optical and Ultraviolet Evolution and Analysis
Sonneborn, G.; Shore, S. N.; Starrfield, S. +3 more
We have obtained optical spectrophotometry of V1974 Cygni (Nova Cygni 1992), the brightest nova since 1975, from day 4 to 540 after visual maximum, which we have combined with ultraviolet spectrophotometry to study the ejecta. We show high quality ultraviolet and optical spectra at each major evolutionary phase, identify the lines present during t…
Hubble Space Telescope Observations of Globular Clusters in M31.I.Color- Magnitude Diagrams, Horizontal Branch Metallicity Dependence, and the Distance to M31
Holtzman, J. A.; Faber, S. M.; Grillmair, C. J. +5 more
This paper presents Hubble Space Telescope observations of four globular clusters in M31 with [Fe/H] ranging from -0.6 to -2.0. The Wide-Field and Planetary Camera-2 (WFPC-2) imaged these clusters through the F555W (V) and F814W (I) filters with total exposure times of 2000 s in each color. The ground-based spectroscopic metallicities are generall…