Search Publications
The Redshift Distribution of Distant Supernovae and Its Use in Probing Reionization
Johnson, Benjamin D.; Haiman, Zoltán; Mesinger, Andrei
We model the number of detectable supernovae (SNe) as a function of redshift at different flux thresholds, making use of the observed properties of local SNe, such as their light curves, fiducial spectra, and peak magnitude distributions. We assume that the star formation rate (SFR) at high redshift traces the formation rate of dark matter halos. …
Oscillations in a solar filament: first observation of long periods in the HeI 584.33 Å line, modelling and diagnostic
Bocchialini, K.; Pouget, G.; Solomon, J.
Three long observations of filaments were carried out in the 584.33 HeI line during MEDOC campaigns in November 2003 and November 2004, by the Coronal Diagnostic Spectrometer onboard SOHO. Their duration was 15-16 h and the temporal resolution was 20 s, allowing measurements of the entire range of periodicities theoretically expected in a filament…
Rotation of Solar Corona from Tracking of Coronal Bright Points
Pevtsov, Alexei A.; Sattarov, Isroil; Karachik, Nina
An automated procedure for identification of coronal bright points is applied to selected EIT images observed at various phases of the solar cycle. The procedure finds about 400 bright points on a single EIT image observed at 195 Å. The positions of the bright points are tracked to study the profile of solar rotation in the solar corona. It is sho…
Deep Photometry of Andromeda Reveals Striking Similarities in the Tidal Stream and Spheroid Populations
Ferguson, Henry C.; Brown, Thomas M.; Rich, R. Michael +5 more
We present a color-magnitude diagram (CMD) for a field in the giant tidal stream of the Andromeda galaxy (M31). These observations, taken with the Advanced Camera for Surveys on the Hubble Space Telescope, are 50% complete at V~30 mag, reaching 1 mag below the oldest main-sequence turnoff. Striking similarities between the stream and a previous sp…
The Globular Cluster System of the Virgo Dwarf Elliptical Galaxy VCC 1087
Geha, M.; Brodie, Jean P.; Beasley, Michael A. +2 more
We present an analysis of the globular cluster (GC) system of the nucleated dwarf elliptical galaxy VCC 1087 in the Virgo Cluster based on Keck LRIS spectroscopy and archival Hubble Space Telescope Advanced Camera for Surveys imaging. We estimate that VCC 1087 hosts a total population of 77+/-19 GCs, which corresponds to a relatively high V-band s…
Chandra and XMM-Newton Observations of a Group of Galaxies, HCG 62
Fukazawa, Yasushi; Ohashi, Takaya; Yamasaki, Noriko Y. +4 more
We present results from Chandra and XMM-Newton observations of a bright group of galaxies, HCG 62. There are two cavities at about 30'' northeast and 20''southwest of the central galaxy in the Chandra image. The energy spectrum shows no significant change in the cavity compared with that in the surrounding region. The radial X-ray profile is descr…
The Hydrogen Exospheric Density Profile Measured with ASPERA-3/NPD
Barabash, S.; Lundin, R.; Holmström, M. +6 more
We have evaluated the Lyman-α limb emission from the exospheric hydrogen of Mars measured by the neutral particle detector of the ASPERA-3 instrument on Mars Express in 2004 at low solar activity (solar activity index = 42, F10.7=100). We derive estimates for the hydrogen exobase density, nH = 1010 m−3, …
An empirical calibration of sulphur abundance in ionised gaseous nebulae
Kehrig, C.; Pérez-Montero, E.; Vílchez, J. M. +1 more
We have derived an empirical calibration of the abundance of S/H as a function of the S{23} parameter, defined using the bright sulphur lines of [SII] and [SIII]. Contrary to the case for the widely used O{23} parameter, the calibration remains single valued up to the abundance values observed in the disk HII regions. The calibration is based on a…
The XMM large scale structure survey: properties and two-point angular correlations of point-like sources
Maccagni, D.; Chiappetti, L.; Valtchanov, I. +9 more
We analyze X-ray sources detected over 4.2 pseudo-contiguous sq. deg. in the 0.5-2 keV and 2-10 keV bands down to fluxes of 2× 10-15 and 8× 10-15 erg s-1 cm-2 respectively, as part of the XMM-Newton Large Scale Structure Survey. The log N-log S in both bands shows a steep slope at bright fluxes, but agre…
Rotationally-resolved spectroscopy of Vesta I: 2 4 µm region
McFadden, L. A.; Rivkin, A. S.; Binzel, R. P. +1 more
We present new infrared (2-4 µm) spectroscopic observations of Vesta obtained in 2001, 2003, and 2004. Together with previously published work, these present a picture of how Vesta's spectrum changes with sub-Earth latitude and longitude. Vesta's albedo and 2-µm band vary regularly with its rotational phase. While establishing the cont…