Search Publications
The Discovery of an Anomalous Subgiant Branch in the Color-Magnitude Diagram of ω Centauri
Ferraro, Francesco R.; Origlia, Livia; Cool, Adrienne M. +4 more
Using deep high-resolution multiband images taken with the Very Large Telescope and the Hubble Space Telescope, we discovered a new anomalous sequence in the color-magnitude diagram of ω Cen. This feature appears as a narrow well-defined subgiant branch (SGB-a), which merges into the main sequence of the dominant cluster population at a magnitude …
Obscuration and Origin of Nuclear X-Ray Emission in FR I Radio Galaxies
Gliozzi, M.; Sambruna, R. M.; Donato, D.
We present X-ray observations of the nuclear region of 25 Fanaroff-Riley type I (FR I) radio galaxies from the 3CRR and B2 catalogs, using data from the Chandra and XMM-Newton archives. We find the presence of a X-ray central compact core (CCCX) in 13/25 sources; in 3/25 sources the detection of a CCCX is uncertain, while in the remaining 9/25 sou…
Field E+A Galaxies at Intermediate Redshifts (0.3 < z < 1)
Franx, Marijn; Kelson, Daniel D.; Illingworth, Garth D. +3 more
We select E+A candidates from a spectroscopic data set of ~800 field galaxies and measure the E+A fraction at 0.3<z<1 to be 2.7%+/-1.1%, a value lower than that in galaxy clusters at comparable redshifts (11%+/-3%). HST WFPC2 imaging for five of our six E+A's shows that they have a heterogeneous parent population: these E+A's span a range in…
Follow-Up Chandra Observations of Three Candidate Tidal Disruption Events
Komossa, S.; Halpern, J. P.; Gezari, S.
Large-amplitude, high-luminosity soft X-ray flares were detected by the ROSAT All-Sky Survey in several galaxies with no evidence of Seyfert activity in their ground-based optical spectra. These flares had the properties predicted for a tidal disruption of a star by a central supermassive black hole. We report Chandra observations of three of thes…
The Effects of Stratification on Oscillating Coronal Loops
Erdélyi, Robert; Mendoza-Briceño, César A.; Sigalotti, Leonardo Di G.
Recent observations by the Solar and Heliospheric Observatory (SOHO) and the Transition Region and Coronal Explorer (TRACE) have confirmed previous theoretical predictions that coronal loops may oscillate. These oscillations and their damping are of fundamental importance, because they can provide diagnostics of the coronal plasma. In the present …
Ultraviolet Light from Young Stars in GEMS Quasar Host Galaxies at 1.8<z<2.75
Heymans, C.; Wolf, C.; Barden, M. +14 more
We have performed Hubble Space Telescope imaging of a sample of 23 high-redshift (1.8<z<2.75) active galactic nuclei (AGNs), drawn from the COMBO-17 survey. The sample contains moderately luminous quasars (MB~-23). The data are part of the Galaxy Evolution from Morphologies and SEDs imaging survey that provides high-resolution opt…
Molecular Gas at High Redshift: Jet-induced Star Formation?
Ekers, R. D.; Sadler, E. M.; Hunstead, R. W. +1 more
We present an alternative interpretation of the observations of BR 1202-0725 at z=4.695 and show that its properties are consistent with a relativistic jet issuing from the quasar core, propagating into the intergalactic medium, and triggering star formation along its path. Prompted by this finding, we reviewed all the z>3 objects detected in m…
Polycyclic Aromatic Hydrocarbon Emission in the 15-21 Micron Region
Allamandola, L. J.; Peeters, E.; Mattioda, A. L. +1 more
Observations from the Spitzer Space Telescope have drawn attention to spectroscopic structure longward of 15 µm that is associated with objects showing prominent unidentified infrared (UIR) bands in the mid-IR. If polycyclic aromatic hydrocarbons (PAHs) are indeed responsible for the UIR features, longer wavelength emission arising from out-…
X-Ray Emission from the Old Pulsar B0950+08
Pavlov, George G.; Zavlin, Vyacheslav E.
We present the timing and spectral analyses of the XMM-Newton data on the 17 Myr old, nearby radio pulsar B0950+08. This observation revealed pulsations of the X-ray flux of PSR B0950+08 at its radio period, P~=253 ms. The pulse shape and pulsed fraction are apparently different at lower and higher energies of the observed 0.2-10 keV energy range,…
On the Lack of Thermal Emission from the Quiescent Black Hole XTE J1118+480: Evidence for the Event Horizon
McClintock, Jeffrey E.; Narayan, Ramesh; Rybicki, George B.
A soft component of thermal emission is very commonly observed from the surfaces of quiescent, accreting neutron stars. We searched with Chandra for such a surface component of emission from the dynamical black hole candidate XTE J1118+480 (=J1118), which has a primary mass M1~8 Msolar. None was found, as one would expect if …