Related papers: Intermediate to low-mass stellar content of Wester…
(Abridged) We present high-resolution HST imaging in the optical (WFPC2) and near-infrared (NICMOS) of a disk region 1 kpc NE of the starburst core in the nearby galaxy M82. This region, M82 ``B,'' has been suspected to be a fossil…
In this paper we report the identification of two new Galactic O2 If*/WN6 stars (WR20aa and WR20c), in the outskirt of the massive young stellar cluster Westerlund 2. The morphological similarity between the near-infrared spectra of the new…
We demonstrate the feasibility of detecting directly low mass stars in unresolved super-star clusters with ages < 10 Myr using near-infrared spectroscopy at modest resolution (R ~ 1000). Such measurements could constrain the ratio of high…
We report the detection of 3 additional Wolf-Rayet stars in the young cluster Westerlund 1. They were selected as emission-line star candidates based on 1 micron narrow-band imaging of the cluster carried out at OPD/LNA (Brazil), and then…
Context. With a mass exceeding several 10^4 solar masses and a rich and dense population of massive stars, supermassive young star clusters represent the most massive star-forming environment that is dominated by the feedback from massive…
We present analysis of HST U,V,I, and Halpha images of the peculiar Local Group irregular galaxy IC 10. The images are used to determine the nature of the stellar products in a portion of the recent starburst in this galaxy. We identified…
Recent optical and IR studies have revealed that the heavily-reddened starburst cluster Westerlund 1 (Wd 1) contains at least 22 Wolf-Rayet (WR) stars, comprising the richest WR population of any galactic cluster. We present results of a…
The interplay between the formation of stars, stellar feedback and cloud properties strongly influences the star formation history of giant molecular clouds. The formation of massive stars leads to a variety of stellar clusters, ranging…
Star clusters are born in a highly compact configuration, typically with radii of less than about 1 pc roughly independently of mass. Since the star-formation efficiency is less than 50 per cent by observation and because the residual gas…
We have carried out WFPC2 V- and I-band imaging of the young LMC cluster NGC 2157. Construction of a color-magnitude diagram and isochrone fitting yields an age of tau = 100 000 000 yrs, a reddening E(B-V) = 0.1 and a distance modulus of…
(abridged) We provide Ks photometry for roughly 39,000 stars and H-band photometry for about 11,000 stars within a field of about 40"x40", centred on Sgr A*. In addition, we provide Ks photometry of about 3,000 stars in a very deep central…
Young star clusters like R136 in the Large Magellanic Cloud and NGC 3603, Westerlund 1, and 2 in the Milky Way are dynamically more evolved than expected based on their current relaxation times. In particular, the combination of a high…
Observational studies are finding stars believed to be relics of the earliest stages of hierarchical mass assembly of the Milky Way (i.e., proto-Galaxy). In this work, we contextualize these findings by studying the masses, ages, spatial…
We report the discovery of a previously unknown massive Galactic star cluster at l=29.22, b=-0.20. Identified visually in mid-IR images from the Spitzer GLIMPSE survey, the cluster contains at least 8 late-type supergiants, based on…
Massive stars exhibit spectroscopic and photometric variability over a wide range of timescales. However the physical mechanisms driving this behaviour remain poorly understood. Westerlund 1 presents an ideal laboratory for studying these…
We present an analysis of the diffuse hard X-ray emission in the core of the young massive Galactic cluster Westerlund 1 based on a 48 ks XMM-Newton observation. Chandra results for the diffuse X-ray emission have indicated a soft thermal…
We present high dispersion echelle spectroscopy of the very luminous, young super star cluster (SSC) `F' in M82, obtained with the 4.2-m William Herschel Telescope (WHT), for the purpose of deriving its dynamical mass and assessing whether…
Deep, near-infrared JHK-maps were observed for 10 nearby, grand-design, spiral galaxies using HAWK-I/VLT to study the distribution of young stellar clusters in them and thereby determine whether strong spiral perturbations can influence…
Multiwavelength observations of the young massive cluster Westerlund 1 have revealed evidence for a large number of OB supergiant and Wolf-Rayet binaries. However, in most cases these findings are based on secondary binary characteristics…
We use deep Hubble Space Telescope photometry of the rich, young (~20-45 Myr-old) star cluster NGC 1818 in the Large Magellanic Cloud to derive its stellar mass function (MF) down to ~0.15 Msun. This represents the deepest robust MF thus…