Search Publications
The Virgo Overdensity Explained
Newberg, Heidi Jo; Donlon, Thomas, II; Weiss, Jake +2 more
We suggest that the Virgo Overdensity of stars in the stellar halo is the result of a radial dwarf galaxy merger that we call the Virgo Radial Merger. Because the dwarf galaxy passed very near to the Galactic center, the debris has a large range of energies but nearly zero L z angular momentum. The debris appears to extend from 5 to 5…
Weak and Compact Radio Emission in Early High-mass Star-forming Regions. II. The Nature of the Radio Sources
Menten, K. M.; Molinari, S.; Wyrowski, F. +9 more
In this study we analyze 70 radio continuum sources that are associated with dust clumps and which are considered to be candidates for the earliest stages of high-mass star formation. The detection of these sources was reported by Rosero et al., who found most of them to show weak (< 1 mJy) and compact (< 0.″6) radio emission. Herein, we use…
Constraining Mass-transfer Histories of Blue Straggler Stars with COS Spectroscopy of White Dwarf Companions
Sills, Alison; Knigge, Christian; Mathieu, Robert D. +4 more
Recent studies show that the majority of blue straggler stars (BSSs) in old open clusters are formed through mass transfer from an evolved star onto a main-sequence companion, resulting in a BSS and white dwarf (WD) in a binary system. We present constraints on the mass transfer histories of two BSS-WD binaries in the open cluster NGC 188, using W…
Rotating Halo Traced by the K-giant Stars from LAMOST and Gaia
Tian, Hao; Xu, Yan; Liu, Chao +1 more
With the help of Gaia DR2, we are able to obtain the full 6D phase space information for stars from the Large Sky Area Multi-Object Fibre Spectroscopic Telescope DR5. With high precision of the position, velocity, and metallicity, the rotation of the local stellar halo is presented using the K-giant stars with [Fe/H] < -1 dex within 4 kpc from …
Ripple Patterns in In-plane Velocities of OB Stars from LAMOST and Gaia
Cheng, Xinlun; Mao, Shude; Liu, Chao +1 more
With about 12,000 OB type stars selected from the LAMOST and Gaia survey, we study their three-dimensional velocity distribution over the range of galactocentric radius from 6 to 15 kpc in the Galactic disk plane. A clear ripple pattern in the radial velocity (V R ) map is shown. The median V R reaches -8 km s-1…
On the Orbital Decay of Globular Clusters in NGC 1052-DF2: Testing a Baryon-only Mass Model
van den Bosch, Frank C.; van Dokkum, Pieter; Dutta Chowdhury, Dhruba
The dark matter content of the ultra-diffuse galaxy NGC 1052-DF2, as inferred from globular cluster (GC) and stellar kinematics, carries a considerable amount of uncertainty, with current constraints also allowing for the complete absence of dark matter. We test the viability of such a scenario by examining whether in a “baryon-only” mass model th…
Testing Shear Recovery with Field Distortion
Zhang, Jun; Li, Xiangchong; Luo, Wentao +7 more
The tilt, rotation, or offset of each CCD with respect to the focal plane, as well as the distortion of the focal plane itself, causes shape distortions in the observed objects, an effect typically known as field distortion (FD). We point out that FD provides a unique way of quantifying the accuracy of cosmic shear measurement. The idea is to stac…
The Effect of Binarity on Circumstellar Disk Evolution
Hinkley, Sasha; Rizzuto, Aaron C.; Kraus, Adam L. +6 more
We present new results on how the presence of stellar companions affects disk evolution based on a study of the 5-11 Myr old Upper Scorpius OB Association. Of the 50 G0-M3 Upper Sco members with disks in our sample, only seven host a stellar companion within 2″ and brighter than K = 15, compared to 35 of 75 members without disks. This matches a tr…
Probing the Gas Content of Late-stage Protoplanetary Disks with N2H+
Zhang, Ke; Bergin, Edwin A.; Huang, Jane +5 more
The lifetime of gas in circumstellar disks is a fundamental quantity that informs our understanding of planet formation. Studying disk gas evolution requires measurements of disk masses around stars of various ages. Because H2 gas is unobservable under most disk conditions, total disk masses are based on indirect tracers such as sub-mm …
Looking Deep into the Rosette Nebula’s Heart: The (Sub)stellar Content of the Massive Young Cluster NGC 2244
Cieza, Lucas A.; Schödel, Rainer; Geers, Vincent C. +5 more
As part of the ongoing effort to characterize the low-mass (sub)stellar population in a sample of massive young clusters, we have targeted the ∼2 Myr old cluster NGC 2244. The distance to NGC 2244 from Gaia DR2 parallaxes is 1.59 kpc, with errors of 1% (statistical) and 11% (systematic). We used the Flamingos-2 near-infrared camera at the Gemini-S…