Search Publications
Measurements of the Hubble Constant with a Two-rung Distance Ladder: Two Out of Three Ain't Bad
Casertano, Stefano; Jones, David O.; Riess, Adam G. +7 more
The three-rung distance ladder, which calibrates Type Ia supernovae (SNe Ia) through stellar distances linked to geometric measurements, provides the highest precision direct measurement of the Hubble constant. In light of the Hubble tension, it is important to test the individual components of the distance ladder. For this purpose, we report a me…
Early Results from GLASS-JWST. VIII. An Extremely Magnified Blue Supergiant Star at Redshift 2.65 in the A2744 Cluster Field
Castellano, Marco; Treu, Tommaso; Frye, Brenda L. +18 more
We report the discovery of an extremely magnified star at redshift z = 2.65 in the James Webb Space Telescope (JWST) NIRISS pre-imaging of the A2744 galaxy-cluster field. The star's background host galaxy lies on a fold caustic of the foreground lens, and the cluster creates a pair of images of the region close to the lensed star. We identified th…
The Local Group Mass in the Light of Gaia
Vasiliev, Eugene; Evans, N. Wyn; Strigari, Louis E. +3 more
High-accuracy proper motions (PMs) of M31 and other Local Group (LG) satellites have now been provided by the Gaia satellite. We revisit the timing argument to compute the total mass M of the LG from the orbit of the Milky Way and M31, allowing for the cosmological constant. We rectify a systematic effect caused by the presence of the Large Magell…
Mapping the Complex Kinematic Substructure in the TW Hya Disk
Andrews, Sean M.; Bae, Jaehan; Bergin, Edwin A. +6 more
We present ALMA observations of CO J = 2 - 1 and CS J = 5 - 4 emission from the disk around TW Hydrae. Both molecules trace a predominantly Keplerian velocity structure, although a slowing of the rotation velocity is detected at the outer edge of the disk beyond ≈140 au in CO emission. This was attributed to the enhanced pressure support from the …
Dynamically Tagged Groups of Metal-poor Stars from the Best and Brightest Survey
Huang, Yang; Casey, Andrew R.; Beers, Timothy C. +9 more
Orbital characteristics based on Gaia Early Data Release 3 astrometric parameters are analyzed for ~4000 metal-poor stars ([Fe/H] ≤ -0.8) compiled from the Best and Brightest survey. Selected as metal-poor candidates based on broadband near- and far-IR photometry, 43% of these stars had medium-resolution (1200 ≲ R ≲ 2000) validation spectra obtain…
Still Brighter than Pre-explosion, SN 2012Z Did Not Disappear: Comparing Hubble Space Telescope Observations a Decade Apart
Foley, Ryan J.; Riess, Adam G.; Kirshner, Robert P. +10 more
Type Iax supernovae (SNe Iax) represent the largest class of peculiar white dwarf supernovae. The type Iax SN 2012Z in NGC 1309 is the only white dwarf supernova with a detected progenitor system in pre-explosion observations. Deep Hubble Space Telescope (HST) images taken before SN 2012Z show a luminous, blue source that we have interpreted as a …
Jet Parameters in the Black Hole X-Ray Binary MAXI J1820+070
Zdziarski, Andrzej A.; Sikora, Marek; Tetarenko, Alexandra J.
We study the jet in the hard state of the accreting black hole (BH) binary MAXI J1820+070. From the available radio-to-optical spectral and variability data, we put strong constraints on the jet parameters. We find while it is not possible to uniquely determine the jet Lorentz factor from the spectral and variability properties alone, we can estim…
Investigating the Nature of the Luminous Ambiguous Nuclear Transient ASASSN-17jz
Filippenko, Alexei V.; Burgasser, Adam J.; Im, Myungshin +31 more
We present observations of the extremely luminous but ambiguous nuclear transient (ANT) ASASSN-17jz, spanning roughly 1200 days of the object's evolution. ASASSN-17jz was discovered by the All-Sky Automated Survey for Supernovae (ASAS-SN) in the galaxy SDSS J171955.84+414049.4 on UT 2017 July 27 at a redshift of z = 0.1641. The transient peaked at…
z 2-9 Galaxies Magnified by the Hubble Frontier Field Clusters. I. Source Selection and Surface Density-Magnification Constraints from >2500 Galaxies
Bouwens, R. J.; Oesch, P.; Illingworth, G. +4 more
We assemble a large comprehensive sample of 2534 z ~ 2, 3, 4, 5, 6, 7, 8, and 9 galaxies lensed by the six clusters from the Hubble Frontier Fields (HFF) program. Making use of the availability of multiple independent magnification models for each of the HFF clusters and alternatively treating one of the models as the "truth," we show that the med…
The Hough Stream Spotter: A New Method for Detecting Linear Structure in Resolved Stars and Application to the Stellar Halo of M31
Williams, Benjamin F.; Ness, Melissa K.; Ibata, Rodrigo A. +5 more
Stellar streams from globular clusters (GCs) offer constraints on the nature of dark matter and have been used to explore the dark matter halo structure and substructure of our Galaxy. Detection of GC streams in other galaxies would broaden this endeavor to a cosmological context, yet no such streams have been detected to date. To enable such expl…