Search Publications
The Effect of the Morphological Quenching Mechanism on Star Formation Activity at 0.5 < z < 1.5 in 3D-HST/CANDELS
Fang, Guanwen; Kong, Xu; Gu, Yizhou +3 more
Several mechanisms for the transformation of blue star-forming to red quiescent galaxies have been proposed, and the green valley (GV) galaxies amid them are widely accepted in a transitional phase. Thus, comparing the morphological and environmental differences of the GV galaxies with early-type disks (ETDs; bulge dominated and having a disk) and…
Mysterious Dust-emitting Object Orbiting TIC 400799224
Kostov, Veselin B.; Powell, Brian P.; Rappaport, Saul A. +24 more
We report the discovery of a unique object of uncertain nature-but quite possibly a disintegrating asteroid or minor planet-orbiting one star of the widely separated binary TIC 400799224. We initially identified the system in data from TESS Sector 10 via an abnormally shaped fading event in the light curve (hereafter "dips"). Follow-up speckle ima…
Possible Evidence of Hydrogen Emission in the First-overtone and Multimode RR Lyrae Variables
Deng, Li-Cai; Liu, Chao; Zhang, Hua-Wei +4 more
The nature of shock waves in nonfundamental mode RR Lyrae stars remains a mystery because of limited spectroscopic observations. We apply a pattern recognition algorithm on spectroscopic data from SDSS and LAMOST and report the first evidence of hydrogen emission in first-overtone (RRc) and multimode (RRd) RR Lyrae stars showing the "first apparit…
Precise diffusion coefficients for white dwarf astrophysics
Caplan, M. E.; Freeman, I. F.
Observations of Galactic white dwarfs with Gaia have allowed for unprecedented modelling of white dwarf cooling, resolving core crystallization, and sedimentary heating from neutron-rich nuclei. These cooling sequences are sensitive to the diffusion coefficients of nuclei in Coulomb plasmas which have order 10 per cent uncertainty and are often no…
The Missing Link? Discovery of Pulsations in the Nitrogen-rich PG 1159 Star PG 1144+005
Jones, David; Handler, Gerald; Sowicka, Paulina +1 more
Up to 98% of all single stars will eventually become white dwarfs-stars that link the history and future evolution of the Galaxy, and whose previous evolution is engraved in their interiors. Those interiors can be studied using asteroseismology, utilizing stellar pulsations as seismic waves. The pulsational instability strips of DA and DB white dw…
X-Ray Constraints on the Hot Gas Content of Early-type Galaxies in Virgo
Jones, Christine; Li, Zhiyuan; Hou, Meicun +2 more
We present a systematic study of the diffuse hot gas around early-type galaxies (ETGs) residing in the Virgo cluster, based on archival Chandra observations. Our representative sample consists of 79 galaxies with low-to-intermediate stellar masses (M* ≈ 109-11 M⊙), a mass range that has not been extensively explore…
Tracing the Ionization Structure of the Shocked Filaments of NGC 6240
Kewley, Lisa J.; Heckman, Timothy M.; Calzetti, Daniela +14 more
We study the ionization and excitation structure of the interstellar medium in the late-stage gas-rich galaxy merger NGC 6240 using a suite of emission-line maps at ~25 pc resolution from the Hubble Space Telescope, Keck/NIRC2 with Adaptive Optics, and the Atacama Large Millimeter/submillimeter Array (ALMA). NGC 6240 hosts a superwind driven by in…
X-Ray-to-radio Offset Inference from Low-count X-Ray Jets
Georganopoulos, Markos; Meyer, Eileen T.; Reddy, Karthik
Observations of positional offsets between the location of X-ray and radio features in many resolved, extragalactic jets indicates that the emitting regions are not cospatial, an important piece of evidence in the debate over the origin of the X-ray emission on kiloparsec scales. The existing literature is nearly exclusively focused on jets with s…
Morphological and kinematical analysis of the double-barred galaxy NGC 3504 using ALMA CO (2-1) data
Miyamoto, Yusuke; Espada, Daniel; Trejo, Alfonso +1 more
We present results obtained from ALMA CO (2-1) data of the double-barred galaxy NGC 3504. With three times higher angular resolution (~0${_{.}^{\prime\prime}}$8) than previous studies, our observations reveal an inner molecular gas bar, a nuclear ring, and four inner spiral arm-like structures in the central 1-kpc region. Furthermore, the CO emiss…
The dense warm ionized medium in the inner Galaxy
Goldsmith, P. F.; Langer, W. D.; Buchbender, C. +6 more
Context. Ionized interstellar gas is an important component of the interstellar medium and its lifecycle. The recent evidence for a widely distributed highly ionized warm interstellar gas with a density intermediate between the warm ionized medium (WIM) and compact H II regions suggests that there is a major gap in our understanding of the interst…