- ID:
- ivo://CDS.VizieR/J/A+A/436/527
- Title:
- UBVIc photometry of NGC 4852
- Short Name:
- J/A+A/436/527
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present wide-field deep UBVIc photometry for the previously unstudied open cluster NGC 4852 down to a limiting magnitude Ic~24, obtained from observations taken with the Wide Field Imager camera on-board the MPG/ESO 2.2m telescope at La Silla (ESO, Chile), in the photometric night of July 7, 2002. These data are used to obtain the first estimate of the cluster basic parameters, to study the cluster spatial extension by means of star counts, and to derive the Luminosity (LF) and Mass Functions (MF). The cluster radius turns out to be 5.0+/-1.0arcmin. The cluster emerges clearly from the field down to V=20mag. At fainter magnitudes, it is completely confused with the general Galactic disk field. The stars inside this region define a young open cluster (200 million years old) 1.1kpc far from the Sun (m-M=11.60, E(B-V)=0.45). The Present Day Mass Functions (PDMF) from the V photometry is one of the most extended in mass obtained to date, and can be represented as a power-law with a slope alpha=2.3+/-0.3 and (the Salpeter MF in this notation has a slope alpha=2.35), in the mass range 3.2<=m/m_{sun}_<=0.6. Below this mass, the MF cannot be considered as representative of the cluster MF, as the cluster merges with the field and therefore the MF is the result of the combined effect of strong irregularities in the stellar background and interaction of the cluster with the dense Galactic field. The cluster total mass at the limiting magnitude results to be 2570+/-210M_{sun}_.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/419/149
- Title:
- UBV(I)c photometry of NGC 6996
- Short Name:
- J/A+A/419/149
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present and discuss broad band CCD UBV(I)c photometry and low resolution spectroscopy for stars in the region of the open cluster NGC 6996, located in the North America Nebula. The new data allow us to tightly constrain the basic properties of this object. We revise the cluster size, which in the past has been significantly underestimated. The width of the Main Sequence is mainly interpreted in terms of differential reddening, and indeed the stars' color excess E(B-V) ranges from 0.43 to 0.65, implying the presence of a significant and evenly distributed dust component. We cross-correlate our optical photometry with near infrared photometry from 2MASS, and by means of spectral classification we are able to build extinction curves for an handful of bright members. We find that the reddening slope and the total to selective absorption ratio Rv toward NGC 6996 are anomalous. Moreover the reddening-corrected colors and magnitudes allow us to derive estimates for the cluster distance and age, which turn out to be 760+/-70pc (V0-MV=9.4+/-0.2) and ~350Myr, respectively. Based on our results, we suggest that NGC 6996 is located in front of the North America Nebula, and does not seem to have any apparent relationship with it.
- ID:
- ivo://CDS.VizieR/J/AN/325/307
- Title:
- UBVIc photometry of NGC 3077 center
- Short Name:
- J/AN/325/307
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present UBVIc photometry of starlike objects in the central region of NGC 3077. The colour-colour and colour-magnitude diagrams of the objects are discussed. Many of the objects under consideration, starlike from the ground, are probably dense young star clusters (super star clusters, SSC). Ages spreading over ~4 to ~150Myr are estimated for most of these objects. Sakai and Madore (2001ApJ...555..280S) found enhanced star formation ~30-125Myr ago also in the halo of this galaxy; thus, high star forming activity has occurred within the entire galaxy (centre and halo) since ~130..150Myr. Having ended in the outer regions about 30Myr ago, it is going on near the centre with full vigour.
- ID:
- ivo://CDS.VizieR/J/A+A/555/A50
- Title:
- UBVIc photometry of stars in Westerlund 2
- Short Name:
- J/A+A/555/A50
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A new X-ray, UBVIc, and JHKs study of the young cluster Westerlund 2 was undertaken to resolve discrepancies tied to the cluster's distance. Existing spectroscopic observations for bright cluster members and new multi-band photometry imply a reddening relation toward Westerlund 2 described by E(U-B)/E(B-V)=0.63+0.02E(B-V). Variable-extinction analyses for Westerlund 2 and nearby IC 2581 based upon spectroscopic distance moduli and ZAMS fitting yield values of R_V_=A_V_/E(B-V)=3.88+/-0.18 and 3.77+/-0.19, respectively, and confirm prior assertions that anomalous interstellar extinction is widespread throughout Carina. The results were confirmed by applying the color-difference method to UBVRIcJHKs data for 19 spectroscopically observed cluster members, yielding R_V_=3.85+/-0.07. The derived distance to Westerlund 2 of d=2.85+/-0.43kpc places the cluster on the far side of the Carina spiral arm. The cluster's age is no more than {tau}~2x10^6^yr as inferred from the cluster's brightest stars and an X-ray (Chandra) cleaned analysis of its pre-main-sequence demographic. Four Wolf-Rayet stars in the cluster core and surrounding corona (WR20a, WR20b, WR20c, and WR20aa) are very likely cluster members, and their inferred luminosities are consistent with those of other late-WN stars in open clusters. The color-magnitude diagram for Westerlund 2 also displays a gap at spectral type B0.5~V with associated color spread at higher and lower absolute magnitudes that might be linked to close binary mergers. These features, in conjunction with the evidence for mass loss from the WR stars, may help to explain the high flux of {gamma}-rays, cosmic rays, and X-rays from the direction toward Westerlund 2.
- ID:
- ivo://CDS.VizieR/J/A+A/548/A125
- Title:
- UBVI data of open cluster Trumpler 27
- Short Name:
- J/A+A/548/A125
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The spiral structure of the Milky Way inside the solar circle is still poorly known because of the high density of the material that causes strong extinction towards the Galactic center. We present results of the first extensive and deep color-color diagram (CCD) photometric survey carried out in the field of the open cluster Trumpler 27, an object immersed in a region of extremely high visual absorption in the constellation of Sagittarius not far from the Galaxy center. The survey covers almost a quarter of square degree. We look for young stars clumps that might plausibly be associated with spiral structure. Wide-field UBVI photometry combined with infrared information allows us to reconstruct the distribution in the reddening and distance of young stars in the field using the CCD and color-magnitude diagrams (CMD).
- ID:
- ivo://CDS.VizieR/J/MNRAS/443/454
- Title:
- UBVIH{alpha} photometry in NGC 1893
- Short Name:
- J/MNRAS/443/454
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a UBVI and H{alpha} photometric study of the young open cluster NGC 1893 in the HII region W8 (IC 410 or Sh 2-236). A total of 65 early-type members are selected from photometric diagrams. A mean reddening of the stars is <E(B-V)>=0.563+/-0.083mag. The published photometric data in the near- and mid-infrared passbands are used to test the reddening law towards the cluster, and we confirm that the reddening law is normal (R_V_=3.1). Zero-age main-sequence fitting gives a distance modulus of V_0_-M_V_= 12.7+/-0.2mag, equivalent to 3.5+/-0.3kpc. From H{alpha} photometry, 125 H{alpha} emission stars and candidates are identified as pre-main-sequence (PMS). The lists of young stellar objects and X-ray sources published by previous studies allow us to select a large number of PMS members down to 1M_{sun}_. Isochrone fitting in the Hertzsprung-Russell diagram gives a turn-off age of 1.5Myr and the median age of 1.9Myr from the PMS members with a spread of ~5Myr. We derive the initial mass function (IMF) for stars with mass larger than 1M_{sun}_. The slope of the IMF ({Gamma}=-1.3+/-0.1) is well consistent with the Salpeter/Kroupa IMF. A total mass of the cluster appears to be in excess of 1300M_{sun}_. Finally, we estimate the mass accretion rate of 82 PMS members in the mass range of 0.6-5M_{sun}_.
- ID:
- ivo://CDS.VizieR/J/MNRAS/438/1451
- Title:
- UBVIH{alpha} photometry of IC 1848
- Short Name:
- J/MNRAS/438/1451
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- IC 1848 is one of the young open clusters in the giant star-forming Cas OB6 association. Several interesting aspects relating to star formation processes in giant star-forming regions attracted us to study the initial mass function (IMF), star formation mode and properties of pre-main-sequence (PMS) stars. A UBVI and H{alpha} photometric study of the young open cluster IC 1848 was conducted as part of the 'Sejong Open Cluster Survey'. We have selected 10^5^ early-type members from photometric diagrams. Their mean reddening is <E(B-V)>=0.660+/-0.054mag. Using the published photometric data with near- and mid-infrared archival data we confirmed the normal reddening law (R_V_=3.1) towards the cluster (IC 1848). A careful zero-age main-sequence fitting gives a distance modulus of V_0_-M_V_=11.7+/-0.2mag, equivalent to 2.2+/-0.2kpc. H{alpha} photometry and the list of young stellar objects identified by Koenig et al. permitted us to select a large number of PMS stars comprising 196 H{alpha} emission stars, 35 H{alpha} emission candidates, 5 Class I, 368 Class II and 24 transition disc candidates. From the Hertzsprung-Russell diagram using stellar evolution models, we estimate an age of 5Myr from several evolved stars and 3Myr from the PMS stars. The IMF was derived from stars with mass larger than 3M_{sun}_, and the slope is slightly steeper ({Gamma}=-1.6+/-0.2) than the Salpeter/Kroupa IMF. Finally, we estimated the mass accretion rate of PMS stars with an ultraviolet excess. The mean mass accretion rate is about 1.4x10^-8^M_{sun}_/yr in the mass range of 0.5-2M_{sun}_, whereas intermediate-mass stars (>=2.5M_{sun}_) exhibit a much higher accretion rate of dM/dt>10^-6^M_{sun}/yr.
- ID:
- ivo://CDS.VizieR/J/AJ/123/1411
- Title:
- UBVIHalpha photometry of NGC 4314 star clusters
- Short Name:
- J/AJ/123/1411
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using Hubble Space Telescope (HST) WFPC2 images, we have obtained U, B, V, I, and H{alpha} photometry for 76 star clusters in the nuclear star-forming ring of the barred spiral galaxy NGC 4314. These clusters are likely associated with an inner inner Lindblad resonance (IILR). The blue colors and H{alpha} emission for most of these clusters imply very young ages of 115 Myr. Age estimates based on several reddening-free parameters indicate that the present epoch of star formation has lasted at least 30Myr. By estimating the masses of stars in the clusters and comparing with the H{alpha} luminosity, we conclude that a significant fraction of ongoing star formation in the nuclear ring of NGC 4314 occurs in clusters. The cluster masses identify these as young open clusters, not young globular clusters.
- ID:
- ivo://CDS.VizieR/J/A+AS/137/233
- Title:
- UBVI imaging photometry of NGC 6231
- Short Name:
- J/A+AS/137/233
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CCD UBVI photometry in the field of the open cluster NGC 6231 was obtained for 1060 stars down to V=19mag. Memberships, reddening, distance and age of this cluster were investigated. Its lower sequence displays a notorious bend at V=13.5mag followed by a high number of faint stars showing a large magnitude spread at constant colour. This distribution of stars does not seem to be produced by a mere accumulation of field stars seen in the direction of the cluster but by a real star excess in the zone. The evidence suggests these stars are serious candidates to be cluster members caught in their way towards the ZAMS. Fitting them with pre main sequence isochrones an age spread of 10Myr is obtained. The luminosity and mass functions were found to be flat for -7.5<M_v_<1.5 and for 3 to 80M_{sun}_ respectively.
- ID:
- ivo://CDS.VizieR/J/MNRAS/398/221
- Title:
- UBVIJHK photometry towards (l=305{deg},b=0{deg})
- Short Name:
- J/MNRAS/398/221
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present optical (UBVIc) observations of a rich and complex field in the Galactic plane towards l~305{deg} and b~0{deg}.
