Non-uniform extinction in young open star clusters

Yadav, R. K. S.; Sagar, Ram

doi:10.1046/j.1365-8711.2001.04754.x

Cited by 30 publications

(55 citation statements)

References 40 publications

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“…Indeed, as shown by, e.g. Yadav & Sagar (2001), the differential reddening tends to increase towards younger ages, in some cases reaching ΔE(B − V) ≈ 1 mag, or ΔA V ≈ 3 mag. Since we cannot derive the extinction for individual stars with 2MASS photometry, we examine the effect of differential reddening simply by means of a reddening vector (Figs.…”

Section: Derivation Of Fundamental Parametersmentioning

confidence: 66%

The wide variety of evolutionary stages among 34 unstudied Teutsch open clusters

Bonatto

Bica

2010

A&A

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Context. Close investigations of unstudied open-cluster candidates may improve the statistics of objects undergoing the dissolution phase. Aims. We plan to settle the nature and derive astrophysical (fundamental, structural, and stellar mass content) parameters for 34 unstudied open cluster candidates from the near-infrared Teutsch list. Methods. The analysis employs 2MASS photometry, field-star decontamination (to enhance the intrinsic colour-magnitude diagram morphology), and colour-magnitude filters (for high contrast in stellar radial density profiles). Results. We find 8 clusters younger than ∼30 Myr, 21 with ages within 100-900 Myr, 3 older than 1 Gyr, and possibly 1 as old as ∼7 Gyr. Part of the sample is affected by reddening as high as A V ∼ 9, and about half is located more than d ∼ 3 kpc away from the Sun, with a few reaching d = 6−9 kpc. The sample contains essentially low-luminosity clusters in the optical, with M V ≈ −3 ± 3. These properties are consistent with their near-infrared origin. Cluster size increases both with Galactocentric distance and height over the plane, which is consistent with the low level of tidal stress (and field contamination) associated with these regions. The average mass density falls off with cluster radius as ρ ∼ R −3 , which in clusters younger than ∼20 Myr and more massive than ∼10 3 M has been interpreted as diffusion-related cluster expansion. Conclusions. Besides the derivation of astrophysical parameters for a sample of unstudied open clusters, in this paper we identify a set of clusters older than several 10 2 Myr, with 4 of them having survived a few Gyr. Surveys of open cluster candidates should be further explored to fill in the gap between the detected and predicted number of clusters. An improved statistic, especially on the population of clusters in highly evolved phases, can be used to investigate cluster formation rates and constrain the dissolution-time scale in the Galaxy.

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Section: Derivation Of Fundamental Parametersmentioning

confidence: 66%

The wide variety of evolutionary stages among 34 unstudied Teutsch open clusters

Bonatto

Bica

2010

A&A

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“…(3) Sodium is known to be only a fair tracer of dust, and our low-resolution spectra do not resolve the individual absorption systems that contribute to the Na i D lines, making it impossible to estimate the effect of line saturation. (4) and (5) The reddening along the specific line of sight to SN 1999gi may differ from the average reddening to the OB association and/or the reddening to specific association members (see, e.g., Yadav & Sagar 2001). Nonetheless, taken together the general agreement of all the estimates makes a compelling case for low reddening to SN 1999gi, with E(BÀV ) = 0.20 mag (comparison with SN 1999em); 0.25 mag (Na i D absorption); 0.15 mag (reddening to OB association); and 0.34 (reddening to H ii region), and an upper reddening limit of E(BÀV ) < 0.45 mag coming from the analysis of the early-time continuum shape.…”

Section: The Reddening Of Sn 1999gimentioning

confidence: 99%

A Study of the Type II-Plateau Supernova 1999[CLC]gi[/CLC] and the Distance to its Host Galaxy, NGC 3184

Leonard

Filippenko

et al. 2002

The Astronomical Journal

153

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We present optical spectra and photometry sampling the first 6 months after discovery of supernova (SN) 1999gi in NGC 3184. SN 1999gi is shown to be a Type II-plateau event with a photometric plateau lasting until about 100 days after discovery. Using the expanding photosphere method (EPM), we derive a distance to SN 1999gi of 11:1 þ2:0 À1:8 Mpc and an explosion date of 1999 December 5:8 þ3:0 À3:1 , or 4:1 þ3:0 À3:1 days prior to discovery. This distance is consistent with a Tully-Fisher distance recently derived to NGC 3184 (D % 11.59 Mpc), but it is somewhat closer than the Cepheid distances recently derived to two galaxies that have generally been assumed to be associated with the group containing NGC 3184 (NGC 3319, D = 13.30 AE 0.55 Mpc, and NGC 3198, D = 13.80 AE 0.51 Mpc). From many lines of evidence, we conclude that SN 1999gi is only minimally reddened. A comparison between the color of SN 1999gi at early times and that of an infinitely hot blackbody restricts the reddening to E(BÀV ) < 0.45 mag, while a comparison between the color evolution of SN 1999gi and the well-observed (and extensively modeled) Type II-P SN 1999em implies an even more restrictive upper reddening limit of E(BÀV ) < 0.3 mag. A variety of other, independent reddening estimates are consistent with these upper limits and yield a probable reddening of E(BÀV ) = 0.21 AE 0.09 mag. We reconsider the upper mass limit (9 þ3 À2 M ) recently placed on the progenitor star of SN 1999gi by Smartt et al. in light of these results. Following the same procedures, but using the new data presented here, we arrive at a less restrictive upper mass limit of 15 þ5 À3 M for the progenitor. The increased upper limit results mainly from the larger distance derived through the EPM than was assumed by the Smartt et al. analyses, which relied on less precise (and less recent) distance measurements to NGC 3184. Finally, we confirm the existence of '' complicated '' P Cygni line profiles in early-time and later photospheric-phase spectra of SN 1999gi. These features, first identified by Baron et al. in spectra of SN 1999em as high-velocity absorptions, in addition to the '' normal '' lower velocity component, are here verified to be true P Cygni profiles consisting of both an absorption trough and an emission peak at early times. In the earliest spectrum, taken less than a day after discovery, the features extend out to nearly À30,000 km s À1 , indicating the existence of very high velocity material in the outer envelope of SN 1999gi.

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“…They show that Berkeley 86 is isolated and projected against an area totally free of gas and dust, which is indicative of low levels of extinction for this cluster. Yadav & Sagar (2001) found that Berkeley 86 suffers non-uniform reddening with colour-excess varying in the range 0.24 < E(B − V) < 1.01, while Forbes (1981) measured a more uniform estimation of E(B − V) = 0.96 ± 0.07. NGC 2244 is located at the centre of the Rosette Nebula.…”

Section: Selected Clustersmentioning

confidence: 98%

“…According to Yadav & Sagar (2001), the correct identification of members is crucial for the assessment of extinction in the direction of the cluster and the most reliable selection is based on kinematic studies (proper motion and radial velocity). DAML02 provides a list of stars with JHK photometry -2MASS catalogue (Cutri et al 2003) -and also the probability of the star belonging to the cluster (P%), which is determined from its proper motion.…”

Section: Data Extraction and Cluster Membershipmentioning

confidence: 99%

“…A bimodal distribution is verified, enabling us to distinguish between members and possible field stars. As proposed by Yadav & Sagar (2001), the pollution by field stars should be smaller if only stars with high values of P% are considered members of the cluster. For each cluster, a minimum probability (P min ) was adopted to help distinguish field stars, as indicated by the dotted lines in the histograms in Fig.…”

Section: Data Extraction and Cluster Membershipmentioning

confidence: 99%

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Probing the anomalous extinction of four young star clusters: the use of colour-excess, main-sequence fitting and fractal analysis

Fernandes

Gregorio-Hetem

Hetem

2012

A&A

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Aims. We studied four young star clusters to characterise their anomalous extinction or variable reddening and asses whether they could be due to contamination by either dense clouds or circumstellar effects. Methods. We evaluated the extinction law (R V ) by adopting two methods: (i) the use of theoretical expressions based on the colourexcess of stars with known spectral type; and (ii) the analysis of two-colour diagrams, where the slope of the observed colour distribution was compared to the normal distribution. An algorithm to reproduce the zero-age main-sequence (ZAMS) reddened colours was developed to derive the average visual extinction (A V ) that provides the closest fit to the observational data. The structure of the clouds was evaluated by means of a statistical fractal analysis, designed to compare their geometric structure with the spatial distribution of the cluster members. Results. The cluster NGC 6530 is the only object of our sample affected by anomalous extinction. On average, the other clusters suffer normal extinction, but several of their members, mainly in NGC 2264, seem to have high R V , probably because of circumstellar effects. The ZAMS fitting provides A V values that are in good agreement with those found in the literature. The fractal analysis shows that NGC 6530 has a centrally concentrated distribution of stars that differs from the substructures found in the density distribution of the cloud projected in the A V map, suggesting that the original cloud was changed by the cluster formation. However, the fractal dimension and statistical parameters of Berkeley 86, NGC 2244, and NGC 2264 indicate that there is a good cloud-cluster correlation, when compared to other works based on an artificial distribution of points.

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Non-uniform extinction in young open star clusters

Cited by 30 publications

References 40 publications

The wide variety of evolutionary stages among 34 unstudied Teutsch open clusters

The wide variety of evolutionary stages among 34 unstudied Teutsch open clusters

A Study of the Type II-Plateau Supernova 1999[CLC]gi[/CLC] and the Distance to its Host Galaxy, NGC 3184

Probing the anomalous extinction of four young star clusters: the use of colour-excess, main-sequence fitting and fractal analysis

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