The Clustered Nature of Star Formation. Pre-Main-Sequence Clusters in the Star-Forming Region NGC 602/N90 in the Small Magellanic Cloud*

Gouliermis, D. A.; Schmeja, S.; Dolphin, Andrew E.; Gennaro, Mario; Tognelli, E.; Moroni, P. G. Prada

doi:10.1088/0004-637x/748/1/64

Cited by 26 publications

(39 citation statements)

References 53 publications

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“…At least seven OB-type stars and numerous lower-mass stars reside in 'sub-cluster 1' (Gouliermis et al 2012), with the stellar density distribution comparable to the distribution of extended X-ray emission (see Fig. 4).…”

Section: Sub-cluster 1: the Core Of Ngc 602amentioning

confidence: 74%

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Discovery of X-Ray Emission From Young Suns in the Small Magellanic Cloud

Oskinova

Sun

Evans

et al. 2013

ApJ

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We report the discovery of extended X-ray emission within the young star cluster NGC 602a in the Wing of the Small Magellanic Cloud (SMC) based on observations obtained with the Chandra X-ray Observatory. X-ray emission is detected from the cluster core area with the highest stellar density and from a dusty ridge surrounding the H ii region. We use a census of massive stars in the cluster to demonstrate that a cluster wind or wind-blown bubble is unlikely to provide a significant contribution to the X-ray emission detected from the central area of the cluster. We therefore suggest that X-ray emission at the cluster core originates from an ensemble of low-and solar-mass pre-main-sequence (PMS) stars, each of which would be too weak in X-rays to be detected individually. We attribute the X-ray emission from the dusty ridge to the embedded tight cluster of the new-born stars known in this area from infrared studies. Assuming that the levels of X-ray activity in young stars in the low-metallicity environment of NGC 602a are comparable to their Galactic counterparts, then the detected spatial distribution, spectral properties, and level of X-ray emission are largely consistent with those expected from low-and solar-mass PMS stars and young stellar objects (YSOs). This is the first discovery of X-ray emission attributable to PMS stars and YSOs in the SMC, which suggests that the accretion and dynamo processes in young, low-mass objects in the SMC resemble those in the Galaxy.

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Section: Sub-cluster 1: the Core Of Ngc 602amentioning

confidence: 74%

“…5). Gouliermis et al (2012) showed that NGC 602a is hierarchically structured, and identified sub-clusters that differ in age, mass, and size (their Table 1). Two of the areas of extended X-ray emission coincide with their two most populous sub-clusters (see Fig.…”

Section: Extended X-ray Emissionmentioning

confidence: 99%

Discovery of X-Ray Emission From Young Suns in the Small Magellanic Cloud

Oskinova

Sun

Evans

et al. 2013

ApJ

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“…Typically, the positions of the PMS stars in the CMD do not overlap with those of the main-sequence stars, and therefore it is quite straightforward for our field-subtraction technique to eliminate completely features that are typical of old populations from the original CMD (e.g., Gouliermis et al 2011Gouliermis et al , 2012. However, our field decontamination method is not optimized for regions of high differential extinction because evolved stars in such regions strongly contaminate the CMD positions of the PMS stars due to reddening.…”

Section: Identification Of the Pre-main-sequence Populationsmentioning

confidence: 99%

STELLAR CLUSTERINGS AROUND “ISOLATED” MASSIVE YSOs IN THE LMC

Stephens

Gouliermis

Looney

et al. 2017

ApJ

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Observations suggest that there is a significant fraction of O-stars in the field of the Milky Way that appear to have formed in isolation or in low mass clusters (<100 M ). The existence of these high-mass stars that apparently formed in the field challenges the generally accepted paradigm, which requires star formation to occur in clustered environments. In order to understand the physical conditions for the formation of these stars, it is necessary to observe isolated high-mass stars while they are still forming. With the Hubble Space Telescope, we observe the seven most isolated massive (>8 M ) young stellar objects (MYSOs) in the Large Magellanic Cloud (LMC). The observations show that while these MYSOs are remote from other MYSOs, OB associations, and even from known giant molecular clouds, they are actually not isolated at all. Imaging reveals ∼100 to several hundred pre-main-sequence (PMS) stars in the vicinity of each MYSO. These previously undetected PMS stars form prominent compact clusters around the MYSOs, and in most cases they are also distributed sparsely across the observed regions. Contrary to what previous high-mass field star studies show, these observations suggest that high-mass stars may not be able to form in clusters with masses less than 100 M . If these MYSOs are indeed the best candidates for isolated high-mass star formation, then the lack of isolation is at odds with random sampling of the IMF. Moreover, while isolated MYSOs may not exist, we find evidence that isolated clusters containing O-stars can exist, which in itself is rare.

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“…Numbers 1 through 4 indicate the positions of the regions whose properties are shown in Table 1. Table columns are as follows: ID number of the region; ID number as given by Gouliermis et al (2012); X and Y coordinates in Figure 8; number of actively accreting PMS stars younger than 5 Myr in the region; their median mass, median age, median Hα luminosity, and median bolometric luminosity. 8 µm.…”

Section: Younger Pms Starsmentioning

confidence: 99%

Photometric Determination of the Mass Accretion Rates of Pre-Main-Sequence Stars. Iv. Recent Star Formation in NGC 602

Marchi

Beccari

Panagia

2013

ApJ

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We have studied the young stellar populations in NGC 602, in the Small Magellanic Cloud, using a novel method that we have developed to combine Hubble Space Telescope photometry in the V , I, and Hα bands. We have identified about 300 pre-main sequence (PMS) stars, all of which are still undergoing active mass accretion, and have determined their physical parameters (effective temperature, luminosity, age, mass and mass accretion rate). Our analysis shows that star formation has been present in this field over the last 60 Myr. In addition, we can recognise at least two clear, distinct, and prominent episodes in the recent past: one about 2 Myr ago, but still ongoing in regions of higher nebulosity, and one (or more) older than 30 Myr, encompassing both stars dispersed in the field and two smaller clusters located about 100 north of the centre of NGC 602. The relative locations of younger and older PMS stars do not imply a causal effect or triggering of one generation on the other. The strength of the two episodes appears to be comparable, but the episode occurring more than 30 Myr ago might have been even stronger than the current one. We have investigated the evolution of the mass accretion rateṀ acc as a function of the stellar parameters finding that logṀ acc −0.6 logt + log m + c, where t is the age of the star, m its mass and c is a decreasing function of the metallicity.

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The Clustered Nature of Star Formation. Pre-Main-Sequence Clusters in the Star-Forming Region NGC 602/N90 in the Small Magellanic Cloud*

Cited by 26 publications

References 53 publications

Discovery of X-Ray Emission From Young Suns in the Small Magellanic Cloud

Discovery of X-Ray Emission From Young Suns in the Small Magellanic Cloud

STELLAR CLUSTERINGS AROUND “ISOLATED” MASSIVE YSOs IN THE LMC

Photometric Determination of the Mass Accretion Rates of Pre-Main-Sequence Stars. Iv. Recent Star Formation in NGC 602

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