FSR 0190: Another old distant Galactic cluster

We are conducting a large programme to classify newly discovered Milky Way star cluster candidates from Froebrich et al. Here we present near-infrared follow-up observations of FSR0190 (α = 20h05m31s.3, δ = 33°34â?²09â?², J2000). The cluster is situated close to the Galactic plane (l = 70°7302, b = +0°9498). It shows a circular shape, and a relatively large number of core helium burning stars - which clearly distinguishes the cluster from the rich field - but no centrally condensed star density profile. We derive an age of more than 7 Gyr, a Galactocentric distance of 10.5 kpc, a distance of 10 kpc from the Sun, and an extinction of AK = 0.8 mag. The estimated mass is at least of the order of 105 Mâ??, and the absolute brightness is MV â?¤ -4.7 mag; both are rather typical properties for Palomar-type globular clusters. © 2007 The Authors. Journal compilation © 2007 RAS

UKIRT follow-up observations of the old open cluster FSR0358 (Kirkpatrick1)

We aim to characterise the properties of the stellar clusters in the Milky Way. Utilising an expectation-maximisation method we determined that the cluster FSR0358, originally discovered by J.D.Kirkpatrick, is the most likely real cluster amongst the cluster candidates from Froebrich et al.. Here we present new deep high resolution near infrared imaging of this object obtained with UKIRT. The analysis of the data reveals that FSR0358 (Kirkpatrick1) is a 5+-2Gyr old open cluster in the outer Milky Way. Its age, metallicity of Z=0.008 and distance from the Galactic Centre of 11.2kpc are typical for the known old open galactic clusters. So far six of the FSR cluster candidates have been identified as having an age above 5Gyr. This shows the significance of this catalogue in enhancing our knowledge of the oldest open clusters in the Galaxy.Comment: 8 pages, 1 table, 5 figures, accepted for publication by MNRAS, a version with higher resolution figures can be found at http://astro.kent.ac.uk/~df

YSO jets in the Galactic Plane from UWISH2: I - MHO catalogue for Serpens and Aquila

Jets and outflows from Young Stellar Objects (YSOs) are important signposts of currently ongoing star formation. In order to study these objects we are conducting an unbiased survey along the Galactic Plane in the 1-0S(1) emission line of molecular hydrogen at 2.122mu using the UK Infrared Telescope. In this paper we are focusing on a 33 square degree sized region in Serpens and Aquila (18deg < l < 30deg; -1.5deg < b < +1.5deg). We trace 131 jets and outflows from YSOs, which results in a 15 fold increase in the total number of known Molecular Hydrogen Outflows. Compared to this, the total integrated 1-0S(1) flux of all objects just about doubles, since the known objects occupy the bright end of the flux distribution. Our completeness limit is 3*10^-18Wm^-2 with 70% of the objects having fluxes of less than 10^-17Wm^-2. Generally, the flows are associated with Giant Molecular Cloud complexes and have a scale height of 25-30pc with respect to the Galactic Plane. We are able to assign potential source candidates to about half the objects. Typically, the flows are clustered in groups of 3-5 objects, within a radius of 5pc. These groups are separated on average by about half a degree, and 2/3rd of the entire survey area is devoid of outflows. We find a large range of apparent outflow lengths from 4arcsec to 130arcsec. If we assume a distance of 3kpc, only 10% of all outflows are of parsec scale. There is a 2.6sigma over abundance of flow position angles roughly perpendicular to the Galactic Plane.Comment: 13pages, 1table (Appendix B not included), 6figures, accepted for publication by MNRAS, a version with higher resolution figures can be found at http://astro.kent.ac.uk/~df

A large scale extinction map of the Galactic Anticenter from 2MASS

We present a 127deg x 63deg extinction map of the Anticenter of the Galaxy, based on and colour excess maps from 2MASS. This 8001 square degree map with a resolution of 4 arcminutes is provided as online material. The colour excess ratio / is used to determine the power law index of the reddening law (\beta) for individual regions contained in the area (e.g. Orion, Perseus, Taurus, Auriga, Monoceros, Camelopardalis, Cassiopeia). On average we find a dominant value of \beta=1.8+-0.2 for the individual clouds, in agreement with the canonical value for the interstellar medium. We also show that there is an internal scatter of \beta values in these regions, and that in some areas more than one dominant \beta value is present. This indicates large scale variations in the dust properties. The analysis of the A_V values within individual regions shows a change in the slope of the column density distribution with distance. This can either be attributed to a change in the governing physical processes in molecular clouds on spatial scales of about 1pc or an A_V dilution with distance in our map.Comment: 18 pages, 29 Figures, 1 Table, Accepted for publication by MNRAS, A version with higher resolution figures can be found at http://astro.kent.ac.uk/~df

About the nature of Mercer14

We used UKIRT near infrared (NIR) broad band JHK photometry, narrow band imaging of the 1-0S(1) molecular hydrogen emission line and mid infrared Spitzer IRAC data to investigate the nature of the young cluster Mercer14. Foreground star counts in decontaminated NIR photometry and a comparison with the Besancon Galaxy Model are performed to estimate the cluster distance. This method yields a distance of 2.5kpc with an uncertainty of about 10% and can be applied to other young and embedded clusters. Mercer14 shows clear signs of ongoing star formation with several detected molecular hydrogen outflows, a high fraction of infrared excess sources and an association to a small gas and dust cloud. Hence, the cluster is less than 4Myrs old and has a line of sight extinction of A_K=0.8mag. Based on the most massive cluster members we find that Mercer14 is an intermediate mass cluster with about 500Mo.Comment: 10pages, 2tables, 5figures, accepted for publication by MNRAS, a version with higher resolution figures can be found at http://astro.kent.ac.uk/~df

Global survey of star clusters in the Milky Way: III. 139 new open clusters at high Galactic latitudes

Context. An earlier analysis of the Milky Way Star Cluster (MWSC) catalogue revealed an apparent lack of old (t � 1 Gyr) open clusters in the solar neighbourhood (d � 1 kpc). Aims. To fill this gap we undertook a search for hitherto unknown star clusters, assuming that the missing old clusters reside at high Galactic latitudes | b | > 20°. Methods. We were looking for stellar density enhancements using a star count algorithm on the 2MASS point source catalogue. To increase the contrast between potential clusters and the field, we applied filters in colour-magnitude space according to typical colour-magnitude diagrams of nearby old open clusters. The subsequent comparison with lists of known objects allowed us to select thus far unknown cluster candidates. For verification they were processed with the standard pipeline used within the MWSC survey for computing cluster membership probabilities and for determining structural, kinematic, and astrophysical parameters. Results. In total we discovered 782 density enhancements, 524 of which were classified as real objects. Among them 139 are new open clusters with ages 8.3 < log (t [yr]) < 9.7, distances d< 3 kpc, and distances from the Galactic plane 0.3 <Z< 1 kpc. This new sample has increased the total number of known high latitude open clusters by about 150%. Nevertheless, we still observe a lack of older nearby clusters up to 1 kpc from the Sun. This volume is expected to still contain about 60 unknown clusters that probably escaped our detection algorithm, which fails to detect sparse overdensities with large angular size

Evolution of Class0 protostars: Models vs. Observations

The rates at which mass accumulates into protostellar cores can now be predicted in numerical simulations. Our purpose here is to develop methods to compare the statistical properties of the predicted protostars with the observable parameters. This requires (1) an evolutionary scheme to convert numerically-derived mass accretion rates into evolutionary tracks and (2) a technique to compare the tracks to the observed statistics of protostars. Here, we use a 3D-Kolmogorov-Smirnov test to quantitatively compare model evolutionary tracks and observations of Class0 protostars. We find that the wide range of accretion functions and timescales associated with gravoturbulent simulations naturally overcome difficulties associated with schemes that use a fixed accretion pattern. This implies that the location of a protostar on an evolutionary track does not precisely determine the present age or final accrued mass. Rather, we find that predictions of the final mass for protostars from observed Tbol-Lbol values are uncertain by a factor of two and that the bolometric temperature is not always a reliable measure of the evolutionary stage. Furthermore, we constrain several parameters of the evolutionary scheme and estimate a lifetime of Class0 sources of 2-6*10^4yrs, which is related to the local free-fall time and thus to the local density at the onset of the collapse. Models with Mach numbers smaller than six are found to best explain the observational data. Generally, only a probability of 70% was found that our models explain the current observations. This is caused by not well understood selection effects in the observational sample and the simplified assumptions in the models.Comment: 13 pages, 3 figures, 2 tables, accepted for publication in MNRA

Free-Floating HI Clouds in the M 81 Group

Recent VLA observations pointed at dwarf spheroidal (dSph) galaxies in the M 81 group reveal a hitherto hidden population of extremely low mass (~1e5 Msol) HI clouds with no obvious optical counterparts. We have searched 10 fields in the M81 group totalling 2.2 square degree, both targeting known dwarf spheroidal galaxies and blank fields around the central triplet. Our observations show that the new population of low-mass HI clouds appears to be confined to a region toward the South-East of the central triplet (at distances of ~100 kpc from M 81). Possible explanations for these free-floating HI clouds are that they are related to the dSphs found to the South-East of M 81, that they belong to the galaxies of the M 81 triplet (equivalent to HVCs), that they are of primordial nature and provide fresh, unenriched material falling into the M 81 group, or that they are tidal debris from the 3-body interaction involving M 81-M 82-NGC 3077. Based on circumstantial evidence, we currently favour the latter explanation.Comment: To appear in the Proceedings of IAU Symp. 244 on "Dark Galaxies and Lost Baryons", eds. J. I. Davies & M. J. Disne