Search Publications
Dynamical Mass Estimates for Five Young Massive Stellar Clusters
Brodie, Jean P.; Hunter, Deidre A.; Larsen, Søren S.
We have obtained high-dispersion spectra for four massive star clusters in the dwarf irregular galaxies NGC 4214 and NGC 4449, using the HIRES spectrograph on the Keck I telescope. Combining the velocity dispersions of the clusters with structural parameters and photometry from images taken with the Hubble Space Telescope, we estimate mass-to-ligh…
NGC 604, the Scaled OB Association (SOBA) Prototype. I. Spatial Distribution of the Different Gas Phases and Attenuation by Dust
Mas-Hesse, J. M.; Pérez, E.; Maíz-Apellániz, J.
We have analyzed Hubble Space Telescope and ground-based data to characterize the different gas phases and their interaction with the massive young cluster in NGC 604, a giant H II region in M33. The warm ionized gas is made out of two components: a high-excitation, high surface brightness H II surface located at the faces of the molecular clouds …
A Snapshot Survey for Gravitational Lenses among z>=4.0 Quasars. I. The z>5.7 Sample
Strauss, Michael A.; Brinkmann, J.; Fan, Xiaohui +7 more
Over the last few years, the Sloan Digital Sky Survey (SDSS) has discovered several hundred quasars with redshift between 4.0 and 6.4. Including the effects of magnification bias, one expects a priori that an appreciable fraction of these objects are gravitationally lensed. We have used the Advanced Camera for Surveys on the Hubble Space Telescope…
Hubble Space Telescope Observations of the Main Sequence of M4
Stetson, P. B.; Rich, R. M.; Shara, M. +8 more
We present new results from a photometric study of the main-sequence stars in M4 (NGC 6121=C1620-264), the closest globular cluster to the Sun. Multifield, multiepoch observations at approximately 1, 2, and 6 core radii were obtained with WFPC2 on the Hubble Space Telescope through either the F606W filter or the F555W (V) and F814W (I) filters. Th…
Hubble Space Telescope Observations of NGC 6240: A Case Study of an Ultraluminous Infrared Galaxy with Obscured Activity
Gerssen, Joris; van der Marel, Roeland P.; Hernquist, Lars +3 more
We present results from a Hubble Space Telescope (HST) study of the morphology and kinematics of NGC 6240. This merging galaxy with a double nucleus is one of the nearest and best-studied ultraluminous infrared galaxies. HST resolves both nuclei into separate components. The distance between the northern and southern optical/near-infrared componen…
Balmer and Metal Absorption Feature Gradients in M32
Worthey, Guy
New data sources are used to assess Lick/IDS feature strength gradients inside the half-light radius Re of the compact Local Group elliptical galaxy M32. A Hubble Space Telescope (HST) STIS spectrum seemed to indicate ionized gas and a very young central stellar population. In fact, this conclusion is entirely spurious because of incomp…
The Evolution of Early-Type Field Galaxies Selected from a NICMOS Map of the Hubble Deep Field North
Dickinson, Mark; Ferguson, Henry C.; Lucas, Ray A. +5 more
The redshift distribution of well-defined samples of distant early-type galaxies offers a means to test the predictions of monolithic and hierarchical galaxy formation scenarios. NICMOS maps of the entire Hubble Deep Field North (HDF-N) in the F110W and F160W filters, when combined with the available Wide Field Planetary Camera 2 (WFPC2) data, all…
Absolute Flux Distribution of the SDSS Standard BD +17°4708
Bohlin, R. C.; Gilliland, R. L.
Secondary flux standards are established by measuring their brightness relative to primary standard stars. The Hubble Space Telescope (HST) primary standards are the three pure-hydrogen white dwarf (WD) flux standards that determine the sensitivity calibration for the Space Telescope Imaging Spectrograph. STIS observations have defined the flux of…
The Araucaria Project: An Improved Distance to the Sculptor Spiral Galaxy NGC 300 from Its Cepheid Variables
Udalski, Andrzej; Soszyński, Igor; Minniti, Dante +8 more
In a previous paper, we reported on the discovery of more than a hundred new Cepheid variables in the Sculptor Group spiral galaxy NGC 300 from wide-field images taken in the B and V photometric bands at ESO/La Silla. In this paper, we present additional VI data, derive improved periods and mean magnitudes for the variables, and construct period-l…
The Nature of the Mid-Infrared Population from Optical Identifications of the ELAIS-S1 Sample
Pozzi, F.; Danese, L.; Alexander, D. M. +16 more
We present a multiwavelength catalog (15 µm, R-band, K-band, and 1.4 GHz flux) plus spectroscopic identifications for 406 15 µm sources detected in the European Large Area ISO Survey (ELAIS) region S1, over the flux density range 0.5<S15µm<150 mJy. Three hundred thirty-two (~82%) sources are optically identified …