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The Milky Way Revealed by Variable Stars. I. Sample Selection of RR Lyrae Stars and Evidence for Merger History
Zhao, Gang; Shi, Jian-Rong; Ablimit, Iminhaji +2 more
In order to study the Milky Way, RR Lyrae (RRL) variable stars identified by Gaia, ASAS-SN, and ZTF sky survey projects have been analyzed as tracers in this work. Photometric and spectroscopic information of 3417 RRLs including proper motions, radial velocity, and metallcity are obtained from observational data of Gaia, LAMOST, GALAH, APOGEE, and…
Probing computational methodologies in predicting mid-infrared spectra for large polycyclic aromatic hydrocarbons
Rigopoulou, D.; García-Bernete, I.; Roche, P. F. +3 more
We extend the prediction of vibrational spectra to large sized polycyclic aromatic hydrocarbon (PAH) molecules comprising up to ~1500 carbon atoms by evaluating the efficiency of several computational chemistry methodologies. We employ classical mechanics methods (Amber and Gaff) with improved atomic point charges, semi-empirical (PM3, and density…
Constraining density and metallicity of the Milky Way's hot gas halo from O VII spectra and ram-pressure stripping
Martynenko, Nickolay
Milky Way's (MW) hot gaseous halo extends up to the Galactic virial radius (~200 kpc) and contains a significant component of baryon mass of the Galaxy. The halo properties can be constrained from X-ray spectroscopic observations and from satellite galaxies' ram-pressure stripping studies. Results of the former method crucially depend on the gas m…
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…