Search Publications
Fluctuation Spectroscopy: A New Probe of Old Stellar Populations
van Dokkum, Pieter G.; Conroy, Charlie
We introduce a new method to determine the relative contributions of different types of stars to the integrated light of nearby early-type galaxies. As is well known, the surface brightness of these galaxies shows pixel-to-pixel fluctuations due to Poisson variations in the number of giant stars. Differential spectroscopy of pixels as a function o…
Discovery of an Ultra-faint Dwarf Galaxy in the Intracluster Field of the Virgo Center: A Fossil of the First Galaxies?
Lee, Myung Gyoon; Jang, In Sung
Ultra-faint dwarf galaxies (UFDs) are newcomers among galaxies, and are the faintest galaxies in the observed universe. To date, they have only been found around the Milky Way Galaxy and M31 in the Local Group. We present the discovery of a UFD in the intracluster field in the core of the Virgo cluster (Virgo UFD1), which is far from any massive g…
Magnetic Flux Density in the Heliosphere through Several Solar Cycles
Balogh, A.; Erdős, G.
We studied the magnetic flux density carried by solar wind to various locations in the heliosphere, covering a heliospheric distance range of 0.3-5.4 AU and a heliolatitudinal range from 80° south to 80° north. Distributions of the radial component of the magnetic field, BR , were determined over long intervals from the Helios, ACE, STE…
Trigonometric Distance and Proper Motion of Iras 20056+3350: A Massive Star-forming Region on the solar Circle
Nakanishi, Hiroyuki; Hayashi, Masahiko; Nakagawa, Akiharu +5 more
We report our measurement of the trigonometric distance and proper motion of IRAS 20056+3350, obtained from the annual parallax of H2O masers. Our distance of D = 4.69+0.65-0.51 kpc, which is 2.8 times larger than the near kinematic distance adopted in the literature, places IRAS 20056+3350 at the leading tip of th…
The Physical Characteristics of the Gas in the Disk of Centaurus A Using the Herschel Space Observatory
Boquien, M.; Roussel, H.; Lebouteiller, V. +12 more
We search for variations in the disk of Centaurus A of the emission from atomic fine structure lines using Herschel PACS and SPIRE spectroscopy. In particular, we observe the [C II](158 µm), [N II](122 and 205 µm), [O I](63 and 145 µm), and [O III](88 µm) lines, which all play an important role in cooling the gas in photo-i…
Constraints on Helium Enhancement in the Globular Cluster M4 (NGC 6121): The Horizontal Branch Test
Catelan, M.; Cortés, C.; Alonso-García, J. +2 more
Recent pieces of evidence have revealed that most, and possibly all, globular star clusters are composed of groups of stars that formed in multiple episodes with different chemical compositions. In this sense, it has also been argued that variations in the initial helium abundance (Y) from one population to the next are also the rule, rather than …
A Comprehensive X-Ray and Multiwavelength Study of the Colliding Galaxy Pair NGC 2207/IC 2163
Homan, J.; Rappaport, S.; Levine, A. +3 more
We present a comprehensive study of the total X-ray emission from the colliding galaxy pair NGC 2207/IC 2163, based on Chandra, Spitzer, and GALEX data. We detect 28 ultraluminous X-ray sources (ULXs), 7 of which were not detected previously because of X-ray variability. Twelve sources show significant long-term variability, with no correlated spe…
X- and γ-Ray Pulsations of the Nearby Radio-faint PSR J1741-2054
Belfiore, A.; Camilo, F.; Marelli, M. +6 more
We report the results of a deep XMM-Newton observation of the radio-faint γ-ray pulsar J1741-2054 and its nebula together with the analysis of five years of Fermi Large Area Telescope (LAT) data. The X-ray spectrum of the pulsar is consistent with an absorbed power law plus a blackbody, originating at least partly from the neutron star cooling. Th…
Near-UV Absorption in Very Cool DA White Dwarfs
Saumon, D.; Holberg, J. B.; Kowalski, P. M.
The atmospheres of very cool, hydrogen-rich white dwarfs (WDs) (T eff < 6000 K) are challenging to model because of the increased complexity of the equation of state, chemical equilibrium, and opacity sources in a low-temperature, weakly ionized dense gas. In particular, many models that assume relatively simple models for the broade…
Low-mass X-Ray Binaries and Globular Clusters Streamers and Arcs in NGC 4278
Fabbiano, G.; D'Abrusco, R.; Brassington, N. J.
We report significant inhomogeneities in the projected two-dimensional spatial distributions of low-mass X-ray binaries (LMXBs) and globular clusters (GCs) of the intermediate mass elliptical galaxy NGC 4278. In the inner region of NGC 4278, a significant arc-like excess of LMXBs extending south of the center at ~50'' in the western side of the ga…