Search Publications
How Comets Work
Blum, J.; Fulle, M.; Rotundi, A.
Two major questions regarding comets have been up to now far from any solution. (i) How is it possible that water-ice sublimation from the nucleus surface does not lead to an insulating crust, stopping every gas and dust ejection within a few days? (ii) How is it possible that the gas flow crossing the refractory surface crust ejects dust particle…
Red and Reddened: Ultraviolet through Near-infrared Observations of Type Ia Supernova 2017erp
Wang, Lifan; Hsiao, E. Y.; Ruiter, Ashley J. +22 more
We present space-based ultraviolet/optical photometry and spectroscopy with the Swift Ultra-Violet/Optical Telescope and Hubble Space Telescope (HST), respectively, along with ground-based optical photometry and spectroscopy and near-infrared spectroscopy of supernova SN 2017erp. The optical light curves and spectra are consistent with a normal SN…
Calibrating Mg II-based Black Hole Mass Estimators with Hβ Reverberation Measurements
Park, Daeseong; Woo, Jong-Hak; Bahk, Hyeonguk
We present the new calibration of black hole mass ({M}BH}) estimators based on the Mg II λ2798 broad emission line using the Hβ reverberation-mapped (RM) sample of 31 active galactic nuclei (AGNs) that have high-quality UV spectra. The updated and enlarged sample at redshift z < 0.16 covers a large dynamic range in {M}BH} …
Evolution of the Stellar Mass-Metallicity Relation. II. Constraints on Galactic Outflows from the Mg Abundances of Quiescent Galaxies
Treu, Tommaso; Ellis, Richard S.; Moran, Sean M. +2 more
We present the stellar mass-[Fe/H] and mass-[Mg/H] relation of quiescent galaxies in two galaxy clusters at z ∼ 0.39 and z ∼ 0.54. We derive the age, [Fe/H], and [Mg/Fe] for each individual galaxy using a full-spectrum fitting technique. By comparing with the relations for z ∼ 0 Sloan Digital Sky Survey galaxies, we confirm our previous finding th…
Phase-space Correlation in Stellar Streams of the Milky Way Halo: The Clash of Kshir and GD-1
Malhan, Khyati; Ibata, Rodrigo A.; Martin, Nicolas F. +3 more
We report the discovery of a 70^\circ long stellar stream in the Milky Way halo, which criss-crosses the well known “GD-1” stream. We show that this new stellar structure (“Kshir”) and GD-1 lie at similar distance, and are remarkably correlated in kinematics. We propose several explanations for the nature of this new structure and its possible ass…
High-precision Dynamical Masses of Pre-main-sequence Stars with ALMA and Gaia
Sheehan, Patrick D.; Tobin, John J.; Wu, Ya-Lin +1 more
The Keplerian rotation in protoplanetary disks can be used to robustly measure stellar masses at very high precision if the source distance is known. We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of spatially and spectrally resolved 12CO (2-1) emission toward the disks around 2MASS J16262774-2527247 (the te…
Using [C II] 158 µm Emission from Isolated ISM Phases as a Star Formation Rate Indicator
Hunt, Leslie K.; Calzetti, Daniela; Bolatto, Alberto D. +17 more
The brightest observed emission line in many star-forming galaxies is the [{{C}} {{II}}] 158 µm line, making it detectable up to z ∼ 7. In order to better understand and quantify the [{{C}} {{II}}] emission as a tracer of star formation, the theoretical ratio between the [{{N}} {{II}}] 205 µm emission and the [{{C}} {{II}}] 158 µ…
Rediscovery of the Sixth Star Cluster in the Fornax Dwarf Spheroidal Galaxy
Bacon, D.; Bechtol, K.; Wang, M. Y. +60 more
Since first noticed by Shapley in 1939, a faint object coincident with the Fornax dwarf spheroidal has long been discussed as a possible sixth globular cluster (GC) system. However, debate has continued over whether this overdensity is a statistical artifact or a blended galaxy group. In this Letter we demonstrate, using deep DECam imaging data, t…
A New Generation of Cool White Dwarf Atmosphere Models. III. WD J2356-209: Accretion of a Planetesimal with an Unusual Composition
Rich, R. M.; Koopmans, L. V. E.; Dufour, P. +3 more
WD J2356-209 is a cool metal-polluted white dwarf whose visible spectrum is dominated by a strong and broad sodium feature. Although it was discovered nearly two decades ago, no detailed and realistic analysis of this star had yet been realized. In the absence of atmosphere models taking into account the nonideal high-density effects arising at th…
A Dramatic Decrease in Carbon Star Formation in M31
Chen, Y.; Dalcanton, J. J.; Girardi, L. +8 more
We analyze resolved stellar near-infrared photometry of 21 Hubble Space Telescope (HST) fields in M31 to constrain the impact of metallicity on the formation of carbon stars. Observations of nearby galaxies show that carbon stars are increasingly rare at higher metallicity. Models indicate that carbon star formation efficiency drops due to the dec…