Search Publications
What Does the Milky Way Look Like?
Hao, C. J.; Xu, Y.; Hou, L. G. +5 more
In spite of much work, the overall spiral structure morphology of the Milky Way remains somewhat uncertain. In the last two decades, accurate distance measurements have provided us with an opportunity to solve this issue. Using the precise locations of very young objects, for the first time, we propose that our galaxy has a multiple-arm morphology…
Implications of the Milky Way Travel Velocity for Dynamical Mass Estimates of the Local Group
Price-Whelan, Adrian M.; Peñarrubia, Jorge; Besla, Gurtina +4 more
The total mass of the Local Group (LG) is a fundamental quantity that enables interpreting the orbits of its constituent galaxies and placing the LG in a cosmological context. One of the few methods that allows inferring the total mass directly is the "Timing Argument," which models the relative orbit of the Milky Way (MW) and M31 in equilibrium. …
First Detection of X-Ray Polarization from the Accreting Neutron Star 4U 1820-303
Kaaret, Philip; Wu, Kinwah; Enoto, Teruaki +117 more
This paper reports the first detection of polarization in the X-rays for atoll-source 4U 1820-303, obtained with the Imaging X-ray Polarimetry Explorer (IXPE) at 99.999% confidence level (CL). Simultaneous polarimetric measurements were also performed in the radio with the Australia Telescope Compact Array. The IXPE observations of 4U 1820-303 wer…
CEERS: Spatially Resolved UV and Mid-infrared Star Formation in Galaxies at 0.2 < z < 2.5: The Picture from the Hubble and James Webb Space Telescopes
Papovich, Casey; Yang, Guang; Finkelstein, Steven L. +38 more
We present the mid-infrared (MIR) morphologies for 64 star-forming galaxies (SFGs) at 0.2 < z < 2.5 with stellar mass M * > 109 M ⊙ using James Webb Space Telescope (JWST) Mid-Infrared Instrument (MIRI) observations from the Cosmic Evolution Early Release Science survey. The MIRI bands span the MIR (7.7-21…
X-Ray Polarization of the BL Lacertae Type Blazar 1ES 0229+200
Kaaret, Philip; Wu, Kinwah; Enoto, Teruaki +111 more
We present polarization measurements in the 2-8 keV band from blazar 1ES 0229+200, the first extreme high synchrotron peaked source to be observed by the Imaging X-ray Polarimetry Explorer (IXPE). Combining two exposures separated by about two weeks, we find the degree of polarization to be ΠX = 17.9% ± 2.8% at an electric-vector positi…
Pegasus W: An Ultrafaint Dwarf Galaxy Outside the Halo of M31 Not Quenched by Reionization
McQuinn, Kristen B. W.; Dolphin, Andrew E.; Cohen, Roger E. +3 more
We report the discovery of an ultrafaint dwarf (UFD) galaxy, Pegasus W, located on the far side of the Milky Way-M31 system and outside the virial radius of M31. The distance to the galaxy is ${915}_{-91}^{+60}$ kpc, measured using the luminosity of horizontal branch stars identified in Hubble Space Telescope optical imaging. The galaxy has a half…
Do Central Compact Objects have Carbon Atmospheres?
Halpern, J. P.; Alford, J. A. J.
Only three of the dozen central compact objects (CCOs) in supernova remnants (SNRs) show thermal X-ray pulsations due to nonuniform surface temperature (hot spots). The absence of X-ray pulsations from several unpulsed CCOs has motivated suggestions that they have uniform-temperature carbon atmospheres (UTCAs), which adequately fit their spectra w…
PHANGS-JWST First Results: The 21 µm Compact Source Population
Sandstrom, Karin M.; Kruijssen, J. M. Diederik; Leroy, Adam K. +24 more
We use PHANGS-James Webb Space Telescope (JWST) data to identify and classify 1271 compact 21 µm sources in four nearby galaxies using MIRI F2100W data. We identify sources using a dendrogram-based algorithm, and we measure the background-subtracted flux densities for JWST bands from 2 to 21 µm. Using the spectral energy distribution (…
PHANGS-JWST First Results: The Influence of Stellar Clusters on Polycyclic Aromatic Hydrocarbons in Nearby Galaxies
Kruijssen, J. M. Diederik; Leroy, Adam K.; Rosolowsky, Erik +28 more
We present a comparison of theoretical predictions of dust continuum and polycyclic aromatic hydrocarbon (PAH) emission with new JWST observations in three nearby galaxies: NGC 628, NGC 1365, and NGC 7496. Our analysis focuses on a total of 1063 compact stellar clusters and 2654 stellar associations previously characterized by the Hubble Space Tel…
Metallicity Distribution Functions of 13 Ultra-faint Dwarf Galaxy Candidates from Hubble Space Telescope Narrowband Imaging
Dolphin, Andrew E.; Martin, Nicolas; Starkenburg, Else +10 more
We present uniformly measured stellar metallicities of 463 stars in 13 Milky Way (MW) ultra-faint dwarf galaxies (UFDs; M V = -7.1 to -0.8) using narrowband CaHK (F395N) imaging taken with the Hubble Space Telescope. This represents the largest homogeneous set of stellar metallicities in UFDs, increasing the number of metallicities in…