Search Publications
On the Viability of the PAH Model as an Explanation of the Unidentified Infrared Emission Features
Zhang, Yong; Kwok, Sun
Polycyclic aromatic hydrocarbon (PAH) molecules are widely considered the preferred candidate for the carrier of the unidentified infrared emission bands observed in the interstellar medium and circumstellar envelopes. In this paper, we report the results of fitting a variety of non-PAH spectra (silicates, hydrogenated amorphous carbon, coal, and …
The M31 Near-infrared Period-Luminosity Relation and its Non-linearity for δ Cep Variables with 0.5 <= log (P) <= 1.7
Lee, Chien-Hsiu; Bender, Ralf; Seitz, Stella +7 more
We present the largest M31 near-infrared (F110W (close to J band), F160W (H band)) Cepheid sample so far. The sample consists of 371 Cepheids with photometry obtained from the Hubble Space Telescope PHAT program. The sample of 319 fundamental mode Cepheids, 16 first overtone Cepheids, and 36 type II Cepheids was identified using the median absolut…
Characterizing the Star Formation of the Low-mass Shield Galaxies from Hubble Space Telescope Imaging
Cannon, John M.; Dolphin, Andrew E.; Skillman, Evan D. +8 more
The Survey of Hi in Extremely Low-mass Dwarfs is an on-going multi-wavelength program to characterize the gas, star formation, and evolution in gas-rich, very low-mass galaxies that populate the faint end of the galaxy luminosity function. The galaxies were selected from the first ∼10% of the Hi Arecibo Legacy Fast ALFA survey based on their low H…
NuSTAR Observations of the Powerful Radio Galaxy Cygnus A
Hailey, Charles J.; Fabian, Andrew C.; Reynolds, Christopher S. +17 more
We present NuSTAR observations of the powerful radio galaxy Cygnus A, focusing on the central absorbed active galactic nucleus (AGN). Cygnus A is embedded in a cool-core galaxy cluster, and hence we also examine archival XMM-Newton data to facilitate the decomposition of the spectrum into the AGN and intracluster medium components. NuSTAR gives a …
Evidence of the Ion Cyclotron Resonance at Proton Kinetic Scales in the Solar Wind
Li, Xing; Roberts, O. W.
The k-filtering and wave polarization techniques are applied to Cluster magnetic field data at four intervals of fast free (not connected to Earth's foreshock) solar wind. In addition to the commonly observed population of magnetic field fluctuations propagating at quasi-perpendicular angles to the global mean field B0 , a population of…
Probing the MSP Prenatal Stage: The Optical Identification of the X-Ray Burster EXO 1745-248 in Terzan 5
Dalessandro, E.; Massari, D.; Mucciarelli, A. +4 more
We report on the optical identification of the neutron star burster EXO 1745-248 in Terzan 5. The identification was performed by exploiting Hubble Space Telescope/Advanced Camera for Surveys images acquired in Director's Discretionary Time shortly after (approximately one month) the Swift detection of the X-ray burst. The comparison between these…
Pits Formation from Volatile Outgassing on 67P/Churyumov-Gerasimenko
Jorda, L.; Lamy, P.; Sierks, H. +8 more
We investigate the thermal evolution of comet 67P/Churyumov-Gerasimenko’s subsurface in the Seth_01 region, where active pits have been observed by the ESA/Rosetta mission. Our simulations show that clathrate destabilization and amorphous ice crystallization can occur at depths corresponding to those of the observed pits in a timescale shorter tha…
Hubble Space Telescope Emission-line Galaxies at z ~ 2: The Mystery of Neon
Trump, Jonathan R.; Schneider, Donald P.; Gronwall, Caryl +6 more
We use near-infrared grism spectroscopy from the Hubble Space Telescope to examine the strength of [Ne III] λ3869 relative to Hβ, [O II] λ3727, and [O III] λ5007 in 236 low-mass (7.5 <~ log (M */M ⊙) <~ 10.5) star-forming galaxies in the redshift range 1.90 < z < 2.35. By stacking the data by stellar mass, we show…
The 2D Distribution of Iron-rich Ejecta in the Remnant of SN 1885 in M31
Fesen, Robert A.; Hamilton, Andrew J. S.; Höflich, Peter A.
We present Hubble Space Telescope (HST) ultraviolet Fe i and Fe ii images of the remnant of Supernova 1885 (S And) which is observed in absorption against the bulge of the Andromeda galaxy, M31. We compare these Fe i and Fe ii absorption line images to previous HST absorption images of S And, of which the highest quality and theoretically cleanest…
Why Does the Apparent Mass of a Coronal Mass Ejection Increase?
Feng, Li; Lu, Lei; Gan, Weiqun +4 more
Mass is one of the most fundamental parameters characterizing the dynamics of a coronal mass ejection (CME). It has been found that CME apparent mass measured from the brightness enhancement in coronagraphs increases during its evolution in the corona. However, the physics behind it is not clear. Does the apparent mass gain come from the outflow f…