Early-type objects in NGC 6611 and the Eagle Nebula

Martayan, C.; Floquet, M.; Hubert, A. M.; Neiner, C.; Frémat, Y.; Baade, D.; Fabregat, J.

doi:10.1051/0004-6361:200809358

Cited by 35 publications

(58 citation statements)

References 30 publications

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“…However, the clusters studied are mainly young, among them NGC 6611. In this cluster, Martayan et al (2008) have showed that some early-type objects remain on the pre-main-sequence. They also found that the rotational velocities of these two kinds of objects differ by about 20%, with ZAMS stars rotating more slowly.…”

Section: Frequency Of Be Stars As a Function Of Local Star Densitymentioning

confidence: 84%

“…With the help of SIMBAD, the previously known Be stars and those found by Album were compared, and the Hα equivalent widths and line strengths were taken from Hummel et al (1999Hummel et al ( , 2001); Martayan et al (2007a), which were similar to the WFI observations of NGC 6611 by Martayan et al (2008). The results are shown in Fig.…”

Section: Efficiency Of Hα Emission Detectionmentioning

confidence: 99%

“…Detection efficiency in equivalent width (top) and peak line strength relative to the continuum (bottom) of Hα emission with WFI slitless spectra. The Hα data are from Hummel et al (1999Hummel et al ( , 2001 and Martayan et al (2007aMartayan et al ( , 2008 and/or UCAC2, USNO catalogues were utilized. In this way, the coordinates of the 7,867 SMC stars mentioned in Sect.…”

Section: Astrometry and Correlation With Oglementioning

confidence: 99%

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A slitless spectroscopic survey for Hαemission-line objects in SMC clusters

Martayan

Baade

Fabregat³

2010

A&A

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Context.A fair fraction of all single early-type stars display emission lines well before their supergiant phase. Very rapid rotation is necessary for these stars to form rotationally supported decretion disks. However, it is unknown whether and which other parameters may be important. Aims. We assess the roles of metallicity and evolutionary age in the appearance of the so-called Be phenomenon. Methods. Slitless CCD spectra were obtained covering the bulk (about 3 square degrees) of the Small Magellanic Cloud. For Hα line-emission twice as strong as the ambient continuum, the survey is complete to spectral type B2/B3 on the main sequence. About 8120 spectra of 4437 stars were searched for emission lines in 84 open clusters, and 370 emission-line stars were found, among them at least 231 close to the main sequence. For 176 of them, photometry is available from the OGLE database. For comparison with a higher-metallicity environment, the Galactic sample of the photometric Hα survey by McSwain & Gies (2005, ApJS, 161, 118) was used.Results. Among early spectral sub-types, Be stars are more frequent by a factor ∼3-5 in the SMC than in the Galaxy. The distribution with spectral type is similar in both galaxies, i.e., not strongly dependent on metallicity. The fraction of Be stars does not seem to vary with local star density. The Be phenomenon mainly sets in towards the end of the main-sequence evolution (this trend may be more pronounced in the SMC); but some Be stars already form with Be-star characteristics. In small subsamples (such as single clusters), even if they appear identical, the fraction of emission-line stars can deviate drastically from the mean. Conclusions. In all probability, the fractional critical angular rotation rate, Ω/Ω c , is one of the main parameters governing the occurrence of the Be phenomenon. If the Be character is only acquired during the course of evolution, the key circumstance is the evolution of Ω/Ω c , which is not only dependent on metallicity but differently so for different mass ranges. As a result, even if the Be phenomenon is driven basically by a single parameter (namely Ω/Ω c ), it can assume a complex multi-parametric appearance. The large cluster-to-cluster differences, which seem stronger than all other variations, serve as a caveat that this big picture may undergo significant second-order modulations (e.g., pulsations, initial angular momentum, etc.).

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Section: Frequency Of Be Stars As a Function Of Local Star Densitymentioning

confidence: 84%

Section: Efficiency Of Hα Emission Detectionmentioning

confidence: 99%

Section: Astrometry and Correlation With Oglementioning

confidence: 99%

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A slitless spectroscopic survey for Hαemission-line objects in SMC clusters

Martayan

Baade

Fabregat³

2010

A&A

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“…The use of spectral types has proven useful for determining age gradients in massive clusters like the Eagle nebula (Martayan et al 2008) and probing the disk evolution toward several Galactic SF regions (e.g. Sicilia-Aguilar et al 2006).…”

Section: Spectral Types and Massesmentioning

confidence: 99%

Spitzer/IRAC view of Sh 2-284

Puga¹,

Hony

Neiner

et al. 2009

A&A

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Aims. Using Spitzer/IRAC observations of a region to be observed by the CoRoT satellite, we have unraveled a new complex starforming region at low metallicity in the outer Galaxy. We perform a study of S284 in order to outline the chain of events in this star-forming region. Methods. We used four-band Spitzer/IRAC photometry as well as Hα imaging obtained with INT/WFC. Combining these data with the optical photometry obtained in the frame of CoRoTs preparation and the 2MASS catalog we analysed the properties and distribution of young stellar objects (YSOs) associated with point-like sources. We also studied the SEDs of regions of extended emission, complementing our dataset with IRAS and MSX data. Results. We find that S284 is unique in several ways: it is very isolated at the end of a spiral arm and both the diffuse dust and ionized emission are remarkably symmetric. We have partially resolved the central clusters of the three bubbles present in this region. Despite the different scales observed in its multiple-bubble morphology, our study points to a very narrow spread of ages among the powering high-mass clusters. In contrast, the particular sawtooth structure of the extended emission at the rim of each ionized bubble harbours either small lower-mass clusters with a younger stellar population or individual young reddened protostars. In particular, triggered star formation is considered to be at work in these regions.

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“…As one of the nearest star-forming regions and one of the most well-observed across the electromagnetic spectrum, the Eagle Nebula is a reference source. The nebula cavity is carved into the molecular cloud by a cluster of 22 ionizing stars earlier than B3 (Dufton et al 2006b) with an estimated age of 1−3 × 10 6 yr (Hillenbrand et al 1993;Dufton et al 2006b;Martayan et al 2008). …”

Section: Introductionmentioning

confidence: 99%

Tracing the energetics and evolution of dust withSpitzer: a chapter in the history of the Eagle Nebula

Flagey

Boulanger

Noriega-Crespo

et al. 2011

A&A

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Context. The Spitzer GLIMPSE and MIPSGAL surveys have revealed a wealth of details about the Galactic plane in the infrared (IR) with orders of magnitude higher sensitivity, higher resolution, and wider coverage than previous IR observations. The structure of the interstellar medium (ISM) is tightly connected to the countless star-forming regions. We use these surveys to study the energetics and dust properties of the Eagle Nebula (M 16), one of the best known star-forming regions. Aims. We present MIPSGAL observations of M 16 at 24 and 70 μm and combine them with previous IR data. The mid-IR image shows a shell inside the well-known molecular borders of the nebula, as in the ISO and MSX observations from 15 to 21 μm. The morphologies at 24 and 70 μm are quite different, and its color ratio is unusually warm. The far-IR image resembles the one at 8 μm that enhances the structure of the molecular cloud and the "pillars of creation". We use this set of IR data to analyze the dust energetics and properties within this template for Galactic star-forming regions. Methods. We measure IR spectral energy distributions (SEDs) across the entire nebula, both within the inner shell and the photodissociation regions (PDRs). We use the DUSTEM model to fit these SEDs and constrain the dust temperature, the dust-size distribution, and the radiation field intensity relative to that provided by the star cluster NGC 6611 (χ/χ 0 ). Results. Within the PDRs, the inferred dust temperature (∼35 K), the dust-size distribution, and the radiation field intensity (χ/χ 0 < 1) are consistent with expectations. Within the inner shell, the dust is hotter (∼70 K). Moreover, the radiation field required to fit the SED is larger than that provided by NGC 6611 (χ/χ 0 > 1). We quantify two solutions to this problem: (1) The size distribution of the dust in the shell is not that of interstellar dust. There is a significant enhancement of the carbon dust-mass in stochastically heated very small grains. (2) The dust emission arises from a hot (∼10 6 K) plasma where both UV and collisions with electrons contribute to the heating. Within this hypothesis, the shell SED may be fit for a plasma pressure p/k ∼ 5 × 10 7 K cm −3 . Conclusions. We suggest two interpretations for the M 16 inner shell: (1) The shell matter is supplied by photo-evaporative flows arising from dense gas exposed to ionized radiation. The flows renew the shell matter as it is pushed out by the pressure from stellar winds. Within this scenario, we conclude that massive-star forming regions such as M 16 have a major impact on the carbon dustsize distribution. The grinding of the carbon dust could result from shattering in grain-grain collisions within shocks driven by the dynamical interaction between the stellar winds and the shell. (2) We also consider a more speculative scenario where the shell is a supernova remnant. In this case, we would be witnessing a specific time in the evolution of the remnant where the plasma pressure and temperature would enable the remnant to coo...

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Early-type objects in NGC 6611 and the Eagle Nebula

Cited by 35 publications

References 30 publications

A slitless spectroscopic survey for Hαemission-line objects in SMC clusters

A slitless spectroscopic survey for Hαemission-line objects in SMC clusters

Spitzer/IRAC view of Sh 2-284

Tracing the energetics and evolution of dust withSpitzer: a chapter in the history of the Eagle Nebula

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