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HST viewing of spectacular star-forming trails behind ESO 137-001
Donahue, Megan; Voit, G. Mark; Fossati, Matteo +8 more
We present the results from the HST WFC3 and ACS data on an archetypal galaxy undergoing ram pressure stripping (RPS), ESO 137-001, in the nearby cluster Abell 3627. ESO 137-001 is known to host a prominent stripped tail detected in many bands from X-rays, H α to CO. The HST data reveal significant features indicative of RPS such as asymmetric dus…
Isochrone fitting of Galactic globular clusters - IV. NGC 6362 and NGC 6723
Gontcharov, George A.; Mosenkov, Aleksandr V.; Khovritchev, Maxim Yu +10 more
We present new isochrone fits to the colour-magnitude diagrams of the Galactic globular clusters NGC 6362 and NGC 6723. We utilize 22 and 26 photometric filters for NGC 6362 and NGC 6723, respectively, from the ultraviolet to mid-infrared using data sets from Hubble Space Telescope, Gaia, unWISE, and other photometric sources. We use models and is…
Systematic errors in the maximum-likelihood regression of Poisson count data: introducing the overdispersed χ2 distribution
Bonamente, Massimiliano
This paper presents a new method to estimate systematic errors in the maximum-likelihood regression of count data. The method is applicable in particular to X-ray spectra in situations where the Poisson log-likelihood, or the Cash goodness-of-fit statistic, indicate a poor fit that is attributable to overdispersion of the data. Overdispersion in P…
Dynamics in the outskirts of four Milky Way globular clusters: it's the tides that dominate
Lewis, Geraint F.; de Boer, Thomas; van der Marel, Roeland P. +17 more
We present the results of a spectroscopic survey of the outskirts of four globular - 1261, NGC 4590, NGC 1904, and NGC 1851 - covering targets within 1° from the cluster centres, with 2dF/AAOmega on the Anglo-Australian Telescope (AAT) and FLAMES on the very large telescope (VLT). We extracted chemo-dynamical information for individual stars, from…
Inhomogeneous Galactic chemical evolution: modelling ultra-faint dwarf galaxies of the Large Magellanic Cloud
Jordan, C. J.; Vincenzo, F.; Ji, A. P. +3 more
Ultra-faint dwarf galaxies (UFDs) are among the oldest and most metal-poor galaxies in the cosmos, observed to contain no gas and a high dark matter mass fraction. Understanding the chemical abundance dispersion in such extreme environments could shed light on the very first generations of stars. We present a novel inhomogeneous chemical evolution…
RR Lyrae stars as probes of the outer Galactic halo: chemical and kinematic analysis of a pilot sample
Grebel, Eva K.; Vivas, A. Katherina; Carlin, Jeffrey L. +4 more
We report the spectroscopic analysis of 20 halo ab-type RR Lyrae stars with heliocentric distances between 15 and 165 kpc, conducted using medium-resolution spectra from the Magellan Inamori Kyocera Echelle (MIKE) spectrograph. We obtain the systemic line-of-sight velocities of our targets with typical uncertainties of 5-10 km s-1 and c…
The extremely X-ray luminous radio-loud quasar CFHQS J142952 + 544717 at z = 6.18 under Chandra high-angular resolution lens
Cheung, C. C.; Stawarz, Ł.; Siemiginowska, A. +6 more
We present the first X-ray observation at sub-arcsecond resolution of the high-redshift (z = 6.18) radio-loud quasar CFHQS J142952 + 544717 (J1429). The ~100 net-count 0.3-7 keV spectrum obtained from ~30 ks Chandra exposure is best fit by a single power-law model with a photon index Γ = 2.0 ± 0.2 and no indication of an intrinsic absorber, implyi…
Where are the missing symbiotic stars? Uncovering hidden symbiotic stars in public catalogues
Akras, Stavros
Theoretical predictions of the population of Galactic symbiotic stars (SySts) are highly inconsistent with the current known population. Despite intense effort over the past decades, observations are still far below the predictions. The majority of known SySts so far are identified based on selection criteria established in the optical regime. The…
Peeking beneath the precision floor - II. Probing the chemo-dynamical histories of the potential globular cluster siblings, NGC 288 and NGC 362
Belokurov, Vasily; Buder, Sven; Monty, Stephanie +8 more
The assembly history of the Milky Way (MW) is a rapidly evolving subject, with numerous small accretion events and at least one major merger proposed in the MW's history. Accreted alongside these dwarf galaxies are globular clusters (GCs), which act as spatially coherent remnants of these past events. Using high precision differential abundance me…
On the origin of UV-dim stars: a population of rapidly rotating shell stars?
Martocchia, S.; Bastian, N.; Saracino, S. +1 more
The importance of stellar rotation in setting the observed properties of young star clusters has become clearer over the past decade, with rotation being identified as the main cause of the observed extended main sequence turn-off (eMSTO) phenomenon and split main sequences. Additionally, young star clusters are observed to host large fractions of…