Search Publications
Synthetic photometry of OB star clusters with stochastically sampled IMFs: analysis of models and HST observations
Grebel, Eva K.; Charlot, Stephane; Wofford, Aida +13 more
We present a pilot library of synthetic NUV, U, B, V, and I photometry of star clusters with stochastically sampled IMFs and ionized gas for initial masses, Mi = 103, 104, and 105 M⊙; t = 1, 3, 4, and 8 Myr; Z = 0.014 and Z = 0.002; and log(US) = -2 and -3. We compare the library wi…
A Quarter Century of Guitar Nebula/Filament Evolution
Kargaltsev, Oleg; Klingler, Noel; Slane, Patrick +6 more
We have collected a new deep Chandra X-Ray Observatory exposure of PSR B2224+65 and the "Guitar Nebula," mapping the complex X-ray structure. This is accompanied by a new Hubble Space Telescope (HST) Hα image of the head of the Guitar. Comparing the HST and Chandra structures in four epochs over 25 yr, we constrain the evolution of the TeV particl…
Low X-ray surface brightness clusters: implications on the scatter of the M-T and L-T relations
Andreon, S.; Moretti, A.; Trinchieri, G.
We aim at studying scaling relations of a small but well-defined sample of galaxy clusters that includes the recently discovered class of objects that are X-ray faint for their mass. These clusters have an average low X-ray surface brightness, a low gas fraction, and are underrepresented (by a factor of 10) in X-ray surveys or entirely absent in S…
The Dark Matter Halo of M54
Grillmair, Carl J.; Carlberg, Raymond G.
M54 is a prototype for a globular cluster embedded in a dark matter halo. Gaia Early Data Release 3 photometry and proper motions separate the old, metal-poor stars from the more metal-rich and younger dwarf galaxy stars. The metal-poor stars dominate the inner 50 pc, with a velocity dispersion profile that declines to a minimum around 30 pc then …
Measuring the smearing of the Galactic 511-keV signal: positron propagation or supernova kicks?
Calore, Francesca; Siegert, Thomas; Panther, Fiona H. +4 more
We use 15 years of $\gamma$-ray data from INTEGRAL/SPI in a refined investigation of the morphology of the Galactic bulge positron annihilation signal. Our spatial analysis confirms that the signal traces the old stellar population in the bulge and reveals for the first time that it traces the boxy bulge and nuclear stellar bulge. Using a 3D smoot…
LARS XIII: High Angular Resolution 21 cm H I Observations of Lyα Emitting Galaxies
Cannon, John M.; Hayes, Matthew; Östlin, Göran +8 more
The Lyα emission line is one of the main observables of galaxies at high redshift, but its output depends strongly on the neutral gas distribution and kinematics around the star-forming regions where UV photons are produced. We present observations of Lyα and 21 cm H I emission at comparable scales with the goal to qualitatively investigate how th…
First evidence of a collision between two unrelated open clusters in the Milky Way
Piatti, Andrés E.; Malhan, Khyati
We report the first evidence of an ongoing collision between two star clusters in our Galaxy, namely IC 4665 and Collinder 350. These are open clusters located at a distance of ~330 pc from the Sun and ~100 pc above the Galactic plane, and they both have prograde motions with only a small difference in their velocities (Collinder 350 moves $\sim 5…
Astrometric star-cluster membership probability: application to the case of M 37 with Gaia EDR3
Bedin, L. R.; Griggio, M.
In this work, starting from the well-accepted relations in literature, we introduce a new formalism to compute the astrometric membership probabilities for sources in star clusters, and we provide an application to the case of the open cluster M 37. The novelty of our approach is a refined - and magnitude-dependent - modelling of the parallax dist…
Optical-Radio Position Offsets Are Inversely Correlated with AGN Photometric Variability
Secrest, Nathan J.
Using photometric variability information from the new Gaia DR3 release, I show for the first time that photometric variability is inversely correlated with the prevalence of optical-radio position offsets in the active galactic nuclei (AGNs) that comprise the International Celestial Reference Frame (ICRF). While the overall prevalence of statisti…
Are the host galaxies of long gamma-ray bursts more compact than star-forming galaxies of the field?
Le Floc'h, E.; Vergani, S. D.; Schneider, B. +2 more
Context. Long gamma-ray bursts (GRBs) offer a promising tool for tracing the cosmic history of star formation, especially at high redshift, where conventional methods are known to suffer from intrinsic biases. Previous studies of GRB host galaxies at low redshift showed that high surface density of stellar mass and high surface density of star for…