Search Publications
Demonstration of a Novel Method for Measuring Mass-loss Rates for Massive Stars
Kobulnicky, Henry A.; Povich, Matthew S.; Chick, William T.
The rate at which massive stars eject mass in stellar winds significantly influences their evolutionary path. Cosmic rates of nucleosynthesis, explosive stellar phenomena, and compact object genesis depend on this poorly known facet of stellar evolution. We employ an unexploited observational technique for measuring the mass-loss rates of O and ea…
Revealing the Broad Line Region of NGC 1275: The Relationship to Jet Power
Gurwell, Mark A.; Punsly, Brian; Marziani, Paola +2 more
NGC 1275 is one of the most conspicuous active galactic nuclei (AGN) in the local universe. The radio jet currently emits a flux density of ∼10 Jy at ∼1 mm wavelengths, down from the historic high of ∼65 Jy in 1980. Yet, the nature of the AGN in NGC 1275 is still controversial. It has been debated whether this is a broad emission line (BEL) Seyfer…
Consistent Iron Abundances Derived from Neutral and Singly Ionized Iron Lines in Ultraviolet and Optical Spectra of Six Warm Metal-poor Stars
Roederer, Ian U.; Sneden, Christopher; Cowan, John J. +3 more
Neutral Fe lines in metal-poor stars yield conflicting abundances depending on whether and how deviations from local thermodynamic equilibrium (LTE) are considered. We have collected new high-resolution and high signal-to-noise ultraviolet (UV) spectra of three warm dwarf stars with [Fe/H] ≈ -2.9 with the Space Telescope Imaging Spectrograph on th…
Vertical Oscillation of a Coronal Cavity Triggered by an EUV Wave
Ji, H. S.; Zhang, Q. M.
In this paper, we report our multiwavelength observations of the vertical oscillation of a coronal cavity on 2011 March 16. The elliptical cavity with an underlying horn-like quiescent prominence was observed by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory. The width and height of the cavity are 150″ and 240″, and the c…
NLTE Analysis of Copper Lines in Different Stellar Populations
Zhao, G.; Shi, J. R.; Yan, H. L. +1 more
The copper abundances of 29 metal-poor stars are determined based on the high-resolution, high-signal-to-noise ratio spectra from the UVES spectrograph at the ESO VLT telescope. Our sample consists of the stars of the Galactic halo, thick- and thin-disk, with [Fe/H] ranging from ∼-3.2 to ∼0.0 dex. The non-local thermodynamic equilibrium (NLTE) eff…
On the Importance of the Nonequilibrium Ionization of Si IV and O IV and the Line of Sight in Solar Surges
Martínez-Sykora, J.; Moreno-Insertis, F.; Nóbrega-Siverio, D.
Surges are ubiquitous cool ejections in the solar atmosphere that often appear associated with transient phenomena like UV bursts or coronal jets. Recent observations from the Interface Region Imaging Spectrograph show that surges, although traditionally related to chromospheric lines, can exhibit enhanced emission in Si IV with brighter spectral …
Galaxy Structure, Stellar Populations, and Star Formation Quenching at 0.6 ≲ z ≲ 1.2
Malhotra, Sangeeta; Pasquali, Anna; Joshi, Bhavin +3 more
We use both photometric and spectroscopic data from the Hubble Space Telescope to explore the relationships among 4000 Å break (D4000) strength, colors, stellar masses, and morphology, in a sample of 352 galaxies with log(M */M ⊙) > 9.44 at 0.6 ≲ z ≲ 1.2. We have identified authentically quiescent galaxies in the UVJ diagr…
ALMA Observations toward the Starburst Dwarf Galaxy NGC 5253. I. Molecular Cloud Properties and Scaling Relations
Bendo, George J.; Hirota, Akihiko; Nakanishi, Kouichiro +3 more
We present high-spatial-resolution (∼0.″2, or ∼3 pc) CO(2-1) observations of the nearest young starburst dwarf galaxy, NGC 5253, taken with the Atacama Large Millimeter/submillimeter Array. We have identified 118 molecular clouds with average values of 4.3 pc in radius and 2.2 km s-1 in velocity dispersion, which comprise the molecular …
Using Star Clusters as Tracers of Star Formation and Chemical Evolution: The Chemical Enrichment History of the Large Magellanic Cloud
Chilingarian, Igor V.; Asa'd, Randa
The star formation (SFH) and chemical enrichment (CEH) histories of Local Group galaxies are traditionally studied by analyzing their resolved stellar populations in a form of color-magnitude diagrams obtained with the Hubble Space Telescope. Star clusters can be studied in integrated light using ground-based telescopes to much larger distances. T…
HD 104860 and HD 192758: Two Debris Disks Newly Imaged in Scattered Light with the Hubble Space Telescope
Augereau, J. -C.; Bryden, G.; Mawet, D. +15 more
We present the first scattered-light images of two debris disks around the F8 star HD 104860 and the F0V star HD 192758, respectively ∼45 and ∼67 pc away. We detected these systems in the F110W and F160W filters through our reanalysis of archival Hubble Space Telescope (HST) NICMOS data with modern starlight-subtraction techniques. Our image of HD…