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The Center of the Core-Cusp Globular Cluster M15: CFHT and HST Observations, ALLFRAME Reductions
Stetson, Peter B.
The central brightness cusps seen in some globular clusters are thought to be the relics of a gravothermal core collapse that occurred in the clusters' past. Recent observations show that the centers of such clusters are bluer than their outskirts, indicating that the stellar populations there are somehow different than those farther out, presumab…
The Hubble Space Telescope Extragalactic Distance Scale Key Project. I. The Discovery of Cepheids and a New Distance to M81
Illingworth, Garth D.; Kennicutt, Robert C.; Madore, Barry F. +12 more
We report on the discovery of 30 new Cepheids in the nearby galaxy M81 based on observations using the Hubble Space Telescope (HST). The periods of these Cepheids lie in the range of 10-55 days, based on 18 independent epochs using the HST wide-band F555W filter. The HST F555W and F785LP data have been transformed to the Cousins standard V and I m…
Distance to the Virgo cluster galaxy M100 from Hubble Space Telescope observations of Cepheids
Illingworth, Garth D.; Kennicutt, Robert C.; Madore, Barry F. +11 more
Accurate distances to galaxies are critical for determining the present expansion rate of the Universe or Hubble constant (H0). An important step in resolving the current uncertainty in H0 is the measurement of the distance to the Virgo cluster of galaxies. New observations using the Hubble Space Telescope yield a distance of…
HST FOS Spectroscopy of M87: Evidence for a Disk of Ionized Gas around a Massive Black Hole
Kriss, Gerard A.; Hartig, George F.; Ford, Holland C. +7 more
Using the Faint Object Spectrograph on the Hubble Space Telescope (HST) to observe the central region of M87, we have obtained spectra covering ~4600-6800 A at a spectral dispersion ~4.4 A per resolution element through the 0.26" diameter entrance aperture. One spectrum was obtained centered on the nucleus of M87 and two centered 0.25" off the nuc…
Postrefurbishment Mission Hubble Space Telescope Images of the Core of the Orion Nebula: Proplyds, Herbig-Haro Objects, and Measurements of a Circumstellar Disk
O'Dell, C. R.; Wen, Zheng
We report on observations of M42 made with the Hubble Space Telescope (HST) immediately after the successful repair and refurbishment mission. Images were made in the strongest optical emission lines of H I, (N II), and (O III) and in a bandpass close to V. In a previous paper, the term proplyd was introduced to describe young stars surrounded by …
Narrowband HST Images of M87: Evidence for a Disk of Ionized Gas around a Massive Black Hole
Kriss, Gerard A.; Bohlin, Ralph C.; Hartig, George F. +7 more
We present HST WFPC2 narrowband Hα + [N II] images of M87 which show a small disk of ionized gas with apparent spiral structure surrounding the nucleus of M87. The jet projects ~19.5^deg^ from the minor axis of the disk, which suggests that the jet is approximately normal to the disk. In a companion Letter, Harms et al. measure radial velocities a…
The Abundant Elements in Interstellar Dust
Savage, Blair D.; Sofia, Ulysses J.; Cardelli, Jason A.
We explore the incorporation of the cosmically abundant species O, C, N, Mg, Si, Fe, and S into interstellar dust. Column densities based on Goddard High Resolution Spectrograph 3.5 km/s resolution measurements from the literature for eight individual absorbing regions toward five lines of sight are used. Corrections are applied as needed in order…
HST Photometry of the Trapezium Cluster
Stauffer, John R.; Prosser, Charles F.; Hartmann, Lee +4 more
We have obtained images of 11 fields in the Trapezium cluster with the Planetary Camera (PC) of the Hubble Space Telescope (HST) in order to extend Herbig & Terndrup's (1986) study of this prototype, dense embedded cluster to fainter magnitudes than is possible from the ground. Using these images, we have identified 319 stars within an area of…
Morphological Studies of the Galaxy Populations in Distant ``Butcher-Oemler'' Clusters with HST. I. AC 114 at Z = 0.31 and Abell 370 at Z = 0.37
Smail, Ian; Ellis, Richard S.; Sharples, Ray M. +1 more
We present the first results of an ongoing program we are undertaking with the Wide Field Camera of the Hubble Space Telescope (HST) to understand the physical origin of the enhanced star formation seen in moderate-redshift (z ~ 0.3-0.4) cluster galaxies. Deep HST exposures have been obtained for the central regions of two rich compact "Butcher- O…
Hubble Space Telescope Imaging of Super--Star Clusters in NGC 1569 and NGC 1705
O'Connell, Robert W.; Gallagher, John S., III; Hunter, Deidre A.
We examine the structural properties of three super-star clusters in the nearby, H I-rich galaxies NGC 1569 and NGC 1705. The clusters, which have total absolute V magnitudes between - 13.3 and - 14.1, appear to be point sources on ground-based images but are partially resolved in new images obtained with the Hubble Space Telescope (HST) Planetary…