Search Publications
On the Distance of Magellanic Clouds: First Overtone Cepheids
Marconi, M.; Bono, G.; Caputo, F. +1 more
We present a detailed comparison between predicted and empirical PLI,K relations and the Wesenheit function for Galactic and Magellanic Cloud (MC) first overtone (FO) Cepheids. We find that zero points predicted by Galactic Cepheid models based on a noncanonical (mild overshooting) mass-luminosity (ML) relation are in very good agreemen…
On the Observational Properties of He-burning Stars: Some Clues on the Tilt of the Horizontal Branch in Metal-rich Clusters
Piotto, G.; Cassisi, S.; Castellani, V. +2 more
We investigate the predicted color-magnitude distribution of metal-rich horizontal-branch (HB) stars, discussing selected theoretical models computed under various assumptions about the star metallicity and the efficiency of superadiabatic convection. We find that canonical zero-age horizontal branches with metallicity larger or of the order of Z=…
Dissecting the Luminosity Function of the Coma Cluster of Galaxies Using Canada-France-Hawaii Telescope Wide-Field Images
Andreon, S.; Cuillandre, J. -C.
We determined the relative spatial density of the Coma Cluster galaxies, selected by luminosity and by central brightness, i.e., the luminosity function bivariate in central brightness. The Coma Cluster and control fields were imaged using the CFH12K (42'×28') and UH8K (28'×28') wide-field cameras at the…
Discovery of Soft X-Ray Emission from Io, Europa, and the Io Plasma Torus
Johnson, Robert E.; Weisskopf, Martin C.; Tennant, Allyn F. +13 more
We report the discovery of soft (0.25-2 keV) X-ray emission from the Galilean satellites Io and Europa, probably Ganymede, and from the Io Plasma Torus (IPT). Bombardment by energetic (greater than 10 keV) H, O, and S ions from the region of the IPT seems to be the likely source of the X-ray emission from the Galilean satellites. According to our …
Discovery of Enhanced Germanium Abundances in Planetary Nebulae with the Far Ultraviolet Spectroscopic Explorer
Dinerstein, Harriet L.; Sterling, N. C.; Bowers, Charles W.
We report the discovery of Ge III λ1088.46 in the planetary nebulae (PNe) SwSt 1, BD +30°3639, NGC 3132, and IC 4593, observed with the Far Ultraviolet Spectroscopic Explorer. This is the first astronomical detection of this line and the first measurement of Ge (Z=32) in PNe. We estimate Ge abundances using S and Fe as reference elements, for a ra…
Lyman Break Galaxies and the Reionization of the Intergalactic Medium
Papovich, Casey; Dickinson, Mark; Ferguson, Henry C.
Near-infrared observations of Lyman break galaxies at redshifts of z~3 are beginning to provide constraints on ages, star formation histories, dust content, metallicities, and stellar masses. At present, uncertainties of more than an order of magnitude are typical for many of these parameters. It is nonetheless interesting to ask what the stellar …
Far-infrared emission from intracluster dust in Abell clusters
Lemke, D.; Klaas, U.; Mattila, K. +1 more
The ISOPHOT instrument aboard ISO has been used to observe extended FIR emission of six Abell clusters. Strip scanning measurements with crossing position angles centered on the clusters were carried out at 120 µ m and 180 µ m. The raw profiles of the I120 µ m/I180 µ m surface brightness ratio includin…
The Nature of Ultraluminous X-Ray Sources in NGC 4565
Xia, X. Y.; Xue, S. J.; Mao, S. +2 more
We report the optical identifications of two X-ray-luminous point sources in the spiral galaxy NGC 4565 based on archive data of Chandra and the Hubble Space Telescope. The central X-ray point source, RX J1236.3+2559, is found to be the nucleus of NGC 4565 with an X-ray luminosity of LX~4.3×1039 ergs s-1. We show t…
Spectral analysis of the sdO K 648 , the exciting star of the planetary nebula Ps 1 in the globular cluster M 15 (NGC 7078 )
Rauch, T.; Werner, K.; Heber, U.
We present a spectral analysis of the sdO central star
Physical Structure of the Proto-Planetary Nebula CRL 618. I. Optical Long-Slit Spectroscopy and Imaging
Sahai, R.; Sánchez Contreras, C.; Gil de Paz, A.
In this paper we present optical long-slit spectroscopy and imaging of the proto-planetary nebula CRL 618. The optical lobes of CRL 618 consist of shock-excited gas, which emits many recombination and forbidden lines, and dust, which scatters light from the innermost regions. From the analysis of the scattered Hα emission, we derive a nebular incl…