Spectral classification and distance determination of stars in nine southern Galactic $\ion{H}{ii}$ regions

Pinheiro, M. C.; Copetti, M. V. F.; Oliveira, Vinicius de Abreu

doi:10.1051/0004-6361/200912937

Cited by 17 publications

(19 citation statements)

References 35 publications

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“…In these diagrams, the slope of the distribution, Notes. Spectral types are from Massey et al (2001) for NGC 6357 and from Persi & Tapia (2008) and Pinheiro et al (2010) for NGC 6334. Asterisk following the name in Col. 1 means that U, B and V data are from this paper.…”

Section: Extinction Lawmentioning

confidence: 99%

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Statistical study of OB stars in NGC 6334 and NGC 6357

Russeil

Zavagno

Adami

et al. 2012

A&A

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Context. Star-forming complexes are large structures exhibiting massive star-formation at different stages of evolution, from dense cores to well-developed H ii regions. They are very interesting for the study of the formation and evolution of stars. NGC 6334 and NGC 6357 are two active and relatively nearby star-forming complexes. From the extinction map and the sub-mm cold dust emission, and because they have similar velocities, these regions are most likely connected. However, located in the direction of the Galactic center their radial velocity is not representative of their distance. An alternative is then to determine the distance of NGC 6334 and NGC 6357 from their stellar content. Aims. Our aim is to perform a census of O-B3 ionising stars in NGC 6334 and NGC 6357, to determine the extinction coefficient, and the distance of both regions. A census of O-B3 stars is an essential basis for estimating the statistical lifetime of the earliest massive star-forming phases. Methods. We performed a U, B, V, and R photometric survey of a large area covering NGC 6334 and NGC 6357 with the VIMOS (ESO-VLT) and the MOSAIC (CTIO) instruments. This allows us to have a complete census of O to B3 stars up to V = 22.6 mag. The OB stars are selected based on their U − B and B − V colors. The most robust extinction coefficient is determined from color−color plots before computing the distance of the OB stars. Results. We find a higher value than typical of the diffuse interstellar medium for R V of 3.53 ± 0.08 and 3.56 ± 0.15 for NGC 6357 and NGC 6334, respectively. Adopting these R V values, the distances of NGC 6357 and NGC 6334 are 1.9 ± 0.4 kpc and 1.7 ± 0.3 kpc. We conclude that, within the error bars, both regions are thus at the same distance of 1.75 kpc (weighted mean). We confirm that the value of R V is linked to the large dust grain content. In particular, we found that there are more very small grains in NGC 6357 than in NGC 6334, suggesting that NGC 6357 could be more evolved than NGC 6334. Placed in the Galactic context, the NGC 6334-NGC 6357 complex appears to be located at the inner edge of the Sagittarius-Carina arm. Our census of O to B3 stars leads to a count of ∼230, which allows us to determine the statistical lifetime of the earliest phases of the massive stars. The starless and the protostellar phases have a mean statistical lifetime of ∼1.5 × 10 4 yr and ∼2.2 × 10 5 yr, respectively.

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Section: Extinction Lawmentioning

confidence: 99%

“…Considering the same plots, the Neckel & Chini (1981) results are consistent with ours (see Table B.3). Bohigas et al (2004) found that for Pismis 24 (NGC 6357) R V = 3.51, and Pinheiro et al (2010) found that R V = 3.5 for stars in NGC 6334.…”

Section: Extinction Lawmentioning

confidence: 99%

Statistical study of OB stars in NGC 6334 and NGC 6357

Russeil

Zavagno

Adami

et al. 2012

A&A

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“…For the distance to NGC 6334 I(N), we adopt 1.3 kpc based on recent H 2 O maser parallax studies: 1.34 +0.15 −0.12 kpc (Reid et al 2014) and 1.26 +0.33 −0.21 kpc (Chibueze et al 2014). In the past, the most commonly used value was 1.7 kpc from photometric estimates for the NGC 6334 region (Neckel 1978;Pinheiro et al 2010), implying a reduction by a factor of 1.7 for derived quantities based on the distance squared, such as mass and luminosity. For example, the total luminosity of NGC 6334 I(N) as measured by Sandell (2000) is now 1.0 × 10 3 L with this revised distance.…”

Section: Introductionmentioning

confidence: 99%

Subarcsecond Imaging of the NGC 6334 I(n) Protocluster: Two Dozen Compact Sources and a Massive Disk Candidate

Hunter

Brogan

Cyganowski

et al. 2014

ApJ

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Using the Submillimeter Array (SMA) and Karl G. Jansky Very Large Array, we have imaged the massive protocluster NGC 6334 I(N) at high angular resolution (0. 5 ∼ 650 AU) from 6 cm to 0.87 mm, detecting 18 new compact continuum sources. Three of the new sources are coincident with previously identified H 2 O masers. Together with the previously known sources, these data bring the number of likely protocluster members to 25 for a protostellar density of ∼700 pc −3 . Our preliminary measurement of the Q-parameter of the minimum spanning tree is 0.82-close to the value for a uniform volume distribution. All of the (nine) sources with detections at multiple frequencies have spectral energy distributions consistent with dust emission, and two (SMA 1b and SMA 4) also have long wavelength emission consistent with a central hypercompact H ii region. Thermal spectral line emission, including CH 3 CN, is detected in six sources: LTE model fitting of CH 3 CN (J = 12-11) yields temperatures of 72-373 K, confirming the presence of multiple hot cores. The fitted LSR velocities range from −3.3 to −7.0 km s −1 , with an unbiased mean square deviation of 2.05 km s −1 , implying a protocluster dynamical mass of 410 ± 260 M . From analysis of a wide range of hot core molecules, the kinematics of SMA 1b are consistent with a rotating, infalling Keplerian disk of diameter 800 AU and enclosed mass of 10-30 M that is perpendicular (within 1• ) to the large-scale bipolar outflow axis. A companion to SMA 1b at a projected separation of 0. 45 (590 AU; SMA 1d), which shows no evidence of spectral line emission, is also confirmed. Finally, we detect one 218.4400 GHz and several 229.7588 GHz Class-I CH 3 OH masers.

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“…The area contains evolved optical but also embedded compact H ii regions. This star was originally classified as a B1 Ib by Neckel (1978); later measurements converted the spectral type into O8 III(f) (Walborn 1982;Maíz-Apellániz et al 2004;Pinheiro et al 2010). So far there has been no hint of an eclipsing orbit.…”

Section: Hd 319702mentioning

confidence: 99%

Eclipsing high-mass binaries

Domínguez¹,

Chini²,

Núñez³

et al. 2013

A&A

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We present the first results of a comprehensive photometric O-star survey performed with a robotic twin refractor at the Universitätssternwarte Bochum located near Cerro Armazones in Chile. For three high-mass stars, Pismis 24-1, CPD −51• 8946, and HD 319702, we determined the period through the Lafler-Kinman algorithm and modelled the light curves within the framework of the Roche geometry. For Pismis 24-1, a previously known eclipsing binary, we provide the first light curves and determined a photometric period of 2.36 days together with an orbital inclination of 61.8• .The best-fitting model solution to the light curves suggests a detached configuration. With a primary temperature of T 1 = 42 520 K we obtained the temperature of the secondary component as T 2 = 41 500 K. The CPD − 51• 8946 system is another known eclipsing binary for which we present a revised photometric period of 1.96 days with an orbital inclination of 58.4• . The system probably has a semi-detached configuration and a mass ratio q = M 1 /M 2 = 2.8. If we adopt a primary temperature of T 1 = 34 550 K, we obtain T 2 = 21 500 K for the secondary component. The HD 319702 system is a newly discovered eclipsing binary member of the young open cluster NGC 6334. The system shows well-defined eclipses favouring a detached configuration with a period of 2.0 days and an orbital inclination of 67.5• . Combining our photometric result with the primary spectral type O8 III(f) (T 1 = 34 000 K) we derive a temperature of T 2 = 25 200 K for the secondary component.

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Spectral classification and distance determination of stars in nine southern Galactic $\ion{H}{ii}$ regions

Cited by 17 publications

References 35 publications

Statistical study of OB stars in NGC 6334 and NGC 6357

Statistical study of OB stars in NGC 6334 and NGC 6357

Subarcsecond Imaging of the NGC 6334 I(n) Protocluster: Two Dozen Compact Sources and a Massive Disk Candidate

Eclipsing high-mass binaries

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