arXiv subjects

A. Moitinho

Publications and source records attributed to A. Moitinho.

42 records · Page 3Linked to original sources

arXiv2005

A photometric study of the old open clusters Berkeley 73, Berkeley 75 and Berkeley 25

CCD BVI photometry of the faint open clusters Berkeley~73, Berkeley~75 and Berkeley~25 are presented. The two latter are previously unstudied clusters to our knowledge. While Berkeley~73 is found to be of intermediate-age (about 1.5 Gyr old), Berkeley~75 and Berkeley~25 are two old clusters, with ages larger than 3.0 Gyr. We provide also estimates of the clusters size. Very interestingly, all these clusters turn out to lie far away from the Galactic Center, at $R_{GC} \geq$ 16 kpc, and quite high onto the Galactic plane, at $|Z_{\odot}| \geq 1.5$ kpc. They are therefore important targets to probe the properties of the structure of the Galaxy in this direction, where the Canis Major over-density has been recently discovered to be located.

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arXiv2005

The intermediate-age open clusters Ruprecht 61, Czernik 32, NGC 2225 and NGC 2262

We present the first $BVI$ CCD photometry to $V=22.0$ of 4 fields centered on the region of the southern Galactic star clusters Ruprecht~61, Czernik~32, NGC 2225 and NGC 2262 and of 4 displaced control fields. These clusters were never studied before, and we provide for the first time estimates of their fundamental parameters, namely radial extent, age, distance and reddening. We find that the four clusters are all of intermediate age (around 1 Gyr), close to the Sun and possess lower than solar metal abundance.

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arXiv2004

NGC 2580 and NGC 2588: Two open clusters in the Third Galactic Quadrant

We present CCD broad band photometric observations in the fields of the Third Galactic Quadrant open clusters NGC 2580 and NGC 2588 ($V(I)_C$ and $UBV(RI)_C$ respectively). From the analysis of our data we found that NGC 2580 is located at a distance of about 4 kpc and its age is close to 160 Myr. As for NGC 2588, it is placed at about 5 kpc from the Sun and is 450 Myr old. This means that NGC 2588 belongs to the extension of the Perseus arm, whereas NGC 2580 is closer to the local arm structure. The luminosity functions (LFs) have been constructed for both clusters down to $V \sim 20$ together with their initial mass functions (IMFs) for stars with masses above $M \sim 1-1.5 M_{\sun}$. The IMF slopes for the most massive bins yielded values of $x \approx 1.3$ for NGC 2580 and $x \approx 2$ for NGC 2588. In the case of this latter cluster we found evidence of a core-corona structure produced probably by dynamical effect. In the main sequences of both clusters we detected gaps, which we suggest could be real features.

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arXiv2003

Searching for unknown open clusters in the Tycho-2 catalog

We present 11 new open cluster candidates found in a systematic search for unknown star clusters using the astrometric and photometric data included in the Tycho2 catalog. The possible existence of these stellar aggregates is supported by the analysis of proper motions, color-magnitude diagrams, stellar density distributions, and by the visual inspection of the Digitized Sky Survey (DSS) plates. With these tools we were able to determine mean absolute proper motions as well as preliminary reddenings, distances and ages for the majority of the candidates. We found that most of them are possibly nearby (closer than about 600 pc) open clusters never studied before.

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arXiv2002

New catalogue of optically visible open clusters and candidates

We have compiled a new catalogue of open clusters in the Galaxy which updates the previous catalogues of Lynga (1987) and of Mermilliod (1995) (included in the WEBDA database). New objects and new data, in particular, data on kinematics (proper motions) that were not present in the old catalogues, have been included. Virtually all the clusters (1537) presently known were included, which represents an increment of about 347 objects relative to the Lynga (1987) catalogue. The catalogue is presented in a single table containing all the important data, which makes it easy to use. The catalogue can be accessed on line either at http://www.iagusp.usp.br/~wilton/ or as an electronic table which will be made available at the CDS.

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arXiv2001

NGC 2362: a Template for Early Stellar Evolution

We present UBVRI photometry for the young open cluster NGC 2362. From analysis of the appropriate color-color and color-magnitude diagrams we derive the fundamental parameters of the NGC 2362 cluster to be: age = 5 (+1-2) Myr, distance = 1480 pc, E(B-V)=0.10 mag. The cluster age was independently determined for both high mass (2.1 - 36Msun) and low mass (0.7 - 1.2Msun) stars with excellent agreement between the ages derived using post-main sequence and pre-main sequence evolutionary tracks for the high and low mass stars respectively. Analysis of this cluster's color-magnitude diagram reveals a well defined pre-main sequence (covering DeltaV ~ 9 magnitudes in V and extending from early A stars to near the hydrogen burning limit) which makes this cluster an ideal laboratory for pre-main sequence evolution studies.

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