Search Publications
Sharpening the Tip of the Red Giant Branch
Madore, Barry F.; Freedman, Wendy L.; Mager, Violet
We introduce a modified detection method for measuring the luminosity of the tip of the red giant branch (TRGB) by introducing the composite magnitude T ≡ I - β[(V - I)xcirc - 1.50], where β is the slope of the tip magnitude as a function of color (or metallicity). The method is specifically designed to account for known systematics due…
Upper Limits on the Masses of 105 Supermassive Black Holes from Hubble Space Telescope/Space Telescope Imaging Spectrograph Archival Data
Beifiori, A.; Dalla Bontà, E.; Corsini, E. M. +4 more
Based on the modeling of the central emission-line width measured over subarcsecond apertures with the Hubble Space Telescope, we present stringent upper bounds on the mass of the central supermassive black hole, M •, for a sample of 105 nearby galaxies (D < 100 Mpc) spanning a wide range of Hubble types (E-Sc) and values of the cent…
Evidence for Quasi-Isotropic Magnetic Fields from Hinode Quiet-Sun Observations
Asensio Ramos, A.
Some recent investigations of spectropolarimetric observations of the Zeeman effect in the Fe I lines at 630 nm carried out with the Hinode solar space telescope have concluded that the strength of the magnetic field vector in the internetwork regions of the quiet Sun is in the hG regime and that its inclination is predominantly horizontal. We cri…
Star Formation in Luminous H II Regions in M33
Relaño, Mónica; Kennicutt, Robert C., Jr.
We present a multiwavelength (ultraviolet, infrared, optical, and CO) study of a set of luminous H II regions in M33: NGC 604, NGC 595, NGC 592, NGC 588, and IC131. We study the emission distribution in the interiors of the H II regions to investigate the relation between the dust emission at 8 µm and 24 µm and the location of the mass…
A Stellar Dynamical Measurement of the Black Hole Mass in the Maser Galaxy NGC 4258
Filippenko, Alexei V.; Ho, Luis C.; Gebhardt, Karl +13 more
We determine the mass of the black hole at the center of the spiral galaxy NGC 4258 by constructing axisymmetric dynamical models of the galaxy. These models are constrained by high spatial resolution imaging and long-slit spectroscopy of the nuclear region obtained with the Hubble Space Telescope, complemented by ground-based observations extendi…
Observations and Nonlinear Force-Free Field Modeling of Active Region 10953
Golub, Leon; van Ballegooijen, Adriaan; Lites, Bruce W. +5 more
We present multiwavelength observations of a simple bipolar active region (NOAA 10953), which produced several small flares (mostly B class and one C8.5 class) and filament activations from April 30 to May 3 in 2007. We also explore nonlinear force-free field (NLFFF) modeling of this region prior to the C8.5 flare on May 2, using magnetograph data…
On the Extended Structure of the Phoenix Dwarf Galaxy
Aparicio, Antonio; Martínez-Delgado, David; Hidalgo, Sebastian L. +1 more
We present the star formation history (SFH) and its variations with galactocentric distance for the Local Group dwarf galaxy of Phoenix. They have been derived from a (F555W, F814W) color-magnitude diagram obtained from WFPC2@HST data, which reaches the oldest main-sequence turnoffs. The IAC-star and IAC-pop codes and the MinnIAC suite have been u…
X-Ray and Infrared Observations of Two Externally Polluted White Dwarfs
Zuckerman, B.; Muno, M. P.; Jura, M. +1 more
With XMM-Newton and the Spitzer Space Telescope, we obtain upper bounds to the X-ray fluxes from G29-38 and GD 362, and the 70 µm flux from G29-38. These data provide indirect evidence that G29-38 is accreting from a tidally disrupted asteroid: it is neither accreting large amounts of hydrogen and helium nor is its surrounding dusty disk bei…
Constraining the Spin-down of the Nearby Isolated Neutron Star RX J0806.4-4123, and Implications for the Population of Nearby Neutron Stars
van Kerkwijk, M. H.; Kaplan, D. L.
The nearby isolated neutron stars (INSs) are a group of seven relatively slowly rotating neutron stars that show thermal X-ray spectra, most with broad absorption features. They are interesting both because they may allow one to determine fundamental neutron-star properties by modeling their spectra, and because they appear to be a large fraction …
Ultraviolet Spectroscopy of Supernovae: The First Two Years of Swift Observations
Panagia, N.; Pian, E.; Gehrels, N. +13 more
We present the entire sample of ultraviolet (UV) spectra of supernovae (SNe) obtained with the Ultraviolet/Optical Telescope (UVOT) on board the Swift satellite during the first two years of observations (2005/2006). A total of 29 UV-grism and 22 V-grism spectra of nine SNe have been collected, of which six are thermonuclear (Type Ia) and three co…