Search Publications
The Star Cluster Mass-Galactocentric Radius Relation: Implications for Cluster Formation
Fan, Zhou; de Grijs, Richard; Cameron, Ewan +1 more
Whether or not the initial star cluster mass function is established through a universal, galactocentric-distance-independent stochastic process, on the scales of individual galaxies, remains an unsolved problem. This debate has recently gained new impetus through the publication of a study that concluded that the maximum cluster mass in a given p…
X-ray Spectral and Optical Properties of a ULX in NGC 4258 (M106)
Balman, S.; Akyuz, A.; Aksaker, N. +3 more
We study the X-ray and optical properties of the ultraluminous X-ray source (ULX) X-6 in the nearby galaxy NGC 4258 (M106) based on the archival XMM-Newton, Chandra, Swift, and Hubble Space Telescope (HST) observations. The source has a peak luminosity of L X ∼ 2 × 1039 erg s-1 in the XMM-Newton observation of 2004…
Dynamical Estimate of Post-main-sequence Stellar Masses in 47 Tucanae
Heyl, Jeremy; Richer, Harvey; Kalirai, Jason +2 more
We use the effects of mass segregation on the radial distribution of different stellar populations in the core of 47 Tucanae to find estimates for the masses of stars at different post-main-sequence evolutionary stages. We take samples of main-sequence (MS) stars from the core of 47 Tucanae, at different magnitudes (I.e., different masses), and us…
Spatial Distribution and Kinematics of the Molecular Material Associated with eta Carinae
Menten, Karl M.; Zapata, Luis A.; Rodríguez, Luis F. +3 more
Single-dish submillimeter observations have recently revealed the existence of a substantial, chemically peculiar molecular gas component located in the innermost circumstellar environment of the very massive luminous blue variable star, η Carinae. Here, we present 5″-resolution interferometric observations of the 1\to 0 rotational transition of h…
Homologous Solar Events on 2011 January 27: Build-up and Propagation in a Complex Coronal Environment
Pick, M.; Démoulin, P.; Zucca, P. +2 more
In spite of the wealth of imaging observations at the extreme-ultraviolet (EUV), X-ray, and radio wavelengths, there are still relatively few cases where all of the imagery is available to study the full development of a coronal mass ejection (CME) event and its associated shock. The aim of this study is to contribute to the understanding of the r…
Spectroscopic Confirmation of the Dwarf Spheroidal Galaxy d0994+71 as a Member of the M81 Group of Galaxies
Simon, Joshua D.; Chiboucas, Kristin; Guhathakurta, Puragra +3 more
We use Keck/DEIMOS spectroscopy to measure the first velocity and metallicity of a dwarf spheroidal (dSph) galaxy beyond the Local Group using resolved stars. Our target, d0944+71, is a faint dSph found in the halo of the massive spiral galaxy M81 by Chiboucas et al. We coadd the spectra of 27 individual stars and measure a heliocentric radial vel…
Spectroscopic Diagnostics of Solar Magnetic Flux Ropes Using Iron Forbidden Line
Cheng, X.; Ding, M. D.
In this Letter, we present Interface Region Imaging Spectrograph Fe xxi 1354.08 Å forbidden line emission of two magnetic flux ropes (MFRs) that caused two fast coronal mass ejections with velocities of ≥1000 km s-1 and strong flares (X1.6 and M6.5) on 2014 September 10 and 2015 June 22, respectively. The extreme-ultraviolet images at t…
New Constraints on the Molecular Gas in the Prototypical HyLIRGs BRI1202-0725 and BRI1335-0417
Momjian, E.; Walter, F.; Riechers, D. A. +6 more
We present Karl G Jansky Very Large Array observations of CO(J=2\to 1) line emission and rest-frame 250 GHz continuum emission of the Hyper-Luminous IR Galaxies (HyLIRGs) BRI 1202-0725 (z = 4.69) and BRI 1335-0417 (z = 4.41), with an angular resolution as high as 0.″15. Our low-order CO observations delineate the cool molecular gas, the fuel for s…
Major-Merger Galaxy Pairs at Z = 0: Dust Properties and Companion Morphology
Domingue, Donovan L.; Cao, Chen; Xu, C. Kevin +4 more
We present an analysis of dust properties of a sample of close major-merger galaxy pairs selected by K s magnitude and redshift. The pairs represent the two populations of spiral-spiral (S+S) and mixed morphology spiral-elliptical (S+E). The Code Investigating GALaxy Emission software is used to fit dust models to the Two Micron All S…
The Optical Variability of SDSS Quasars from Multi-epoch Spectroscopy. III. A Sudden UV Cutoff in Quasar SDSS J2317+0005
Prochaska, J. Xavier; Ma, Jingzhe; Malkan, Matthew A. +6 more
We have collected near-infrared to X-ray data of 20 multi-epoch heavily reddened SDSS quasars to investigate the physical mechanism of reddening. Of these, J2317+0005 is found to be a UV cutoff quasar. Its continuum, which usually appears normal, decreases by a factor 3.5 at 3000 Å, compared to its more typical bright state during an interval of 2…