Photometric determination of the mass accretion rates of pre-mainsequence stars - III. Results in the Large Magellanic Cloud

Spezzi, L.; Marchi, Guido De; Panagia, N.; Sicilia‐Aguilar, A.; Ercolano, Barbara

doi:10.1111/j.1365-2966.2011.20130.x

Cited by 40 publications

(69 citation statements)

References 109 publications

(242 reference statements)

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“…This supports the idea that disk properties show a dependence on stellar properties. Together with recent studies indicating that the properties of the given star-forming environment (such as metallicity and presence of of strong UV radiation fields) may affect disk evolution (Spezzi et al 2012;De Marchi et al 2011a,b), our results stress the important unknowns that still subsist in our current theory of disk evolution and planet formation. This paper paves the way for future studies on these open questions using larger YSO samples detected with the HGBS in other star forming-regions, such as Cha I and Serpens.…”

Section: Discussionsupporting

confidence: 83%

TheHerschelGould Belt Survey in Chamaeleon II

Spezzi

Cox

Prusti

et al. 2013

A&A

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Context. We report on the Herschel Gould Belt survey (HGBS) of the Chamaeleon II (Cha II) star-forming region, focusing on the detection of Class I to III young stellar objects (YSOs). Aims. We aim at characterizing the circumstellar material around these YSOs and at understanding which disk parameters are most likely constrained by the new HGBS data, which are expected to be crucial for studying the transition from optically thick disks to evolved debris-type disks. Methods. We recovered 29 of the 63 known YSOs in Cha II with a detection in at least one of the PACS/SPIRE pass-bands: 3 Class I YSOs (i.e.,100%), 1 flat source (i.e., 50%), 21 Class II objects (i.e., 55%), 3 Class III objects (i.e, 16%), and the unclassified farinfrared source IRAS 12522-7640. We explored PACS/SPIRE colors of this sample and modeled their spectral energy distributions (SEDs) from the optical to Herschel's wavelengths with the RADMC-2D radiative transfer code. Results. We find that YSO colors are typically confined to the following ranges: −0.7 log (F 70 /F 160 ) 0.5, −0.5 log (F 160 /F 250 ) 0.6, 0.05 log(F 250 /F 350 ) 0.25 and −0.1 log (F 350 /F 500 ) 0.5. These color ranges are expected to be only marginally contaminated by extragalactic sources and field stars and, hence, provide a useful YSO selection tool when applied together. We were able to model the SED of 26 of the 29 detected YSOs. We discuss the degeneracy/limitations of our SED fitting results and adopted the Bayesian method to estimate the probability of different values for the derived disk parameters. The Cha II YSOs present typical disk inner radii 0.1 AU, as previously estimated in the literature on the basis of Spitzer data. Our probability analysis shows that, thanks to the new Herschel data, the lower limits to the disk mass (M disk ) and characteristic radius (R C ) are well constrained, while the flaring angle (1 + φ) is only marginally constrained. The lower limit to R C is typically around 50 AU. The lower limits to M disk are proportional to the stellar masses with a typical 0.3% ratio, i.e., in the range estimated in the literature for young Class II stars and brown dwarfs across a broad range of stellar masses. The estimated flaring angles, although very uncertain, point toward very flat disks (1 + φ 1.2), as found for low-mass M-type YSO samples in other star-forming regions. Thus, our results support the idea that disk properties show a dependence on stellar properties.

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Section: Discussionsupporting

confidence: 83%

TheHerschelGould Belt Survey in Chamaeleon II

Spezzi

Cox

Prusti

et al. 2013

A&A

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“…Of course, it changes the distribution of mass accretion rates. The values are higher for a model with, for example, b = 0.82, as observed by Spezzi et al (2012) at some star-forming regions of the Large Magellanic Cloud. However, the mass accretion rate as a function of time (Eq.…”

Section: Resultsmentioning

confidence: 60%

Investigating the rotational evolution of young, low-mass stars using Monte Carlo simulations

Vasconcelos

Bouvier

2015

A&A

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Context. Young stars rotate well below break-up velocity, which is thought to result from the magnetic coupling with their accretion disk. Aims. We investigate the rotational evolution of young stars under the disk-locking hypothesis through Monte Carlo simulations. Methods. Our simulations included 280 000 stars, each of which was initially assigned a mass, a rotational period, and a mass accretion rate. The mass accretion rate depends on both mass and time, following power-law indices of 1.4 and −1.5, respectively. A mass-dependent accretion threshold was defined below which a star was considered as diskless, which resulted in a distribution of disk lifetimes that matches observations. Stars were evolved at constant angular spin rate while accreting and at constant angular momentum when they became diskless. Results. Starting with a bimodal distribution of periods for disk and diskless stars, we recovered the bimodal period distribution seen in several young clusters. The short-period peak mostly consists of diskless stars, and the long-period peak is mainly populated by accreting stars. Both distributions, however, present a long tail toward long periods, and a population of slowly rotating diskless stars is observed at all ages. We reproduced the observed correlations between disk fraction and spin rate, as well as between IR excess and rotational period. The period-mass relation we derived from the simulations only shows the same global trend as observed in young clusters when we released the disk-locking assumption for the lowest mass stars. Finally, we find that the time evolution of median specific angular momentum follows a power-law index of −0.65 for accreting stars, as expected from disk locking, and of −0.53 for diskless stars, a shallower slope that results from a wide distribution of disk lifetimes. At the end of the accretion phase, our simulations reproduce the angular momentum distribution of the low-mass members of the 13 Myr h Per cluster. Conclusions. Using observationally documented distributions of disk lifetimes, mass accretion rates, and initial rotation periods, and evolving an initial population from 1 to 12 Myr, we reproduced the main characteristics of pre-main sequence angular momentum evolution, which supports the disk-locking hypothesis.

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“…Since the mass accretion rateṀ acc scales approximately linearly with the mass of the objects (e.g. De Marchi et al 2011aMarchi et al , 2013aBarentsen et al 2011;Spezzi et al 2012), the large difference in the sampled masses in the two datasets is a plausible explanation for the difference in the observed distribution ofṀ acc .…”

Section: Mass Accretion Ratesmentioning

confidence: 99%

Mass accretion rates from multiband photometry in the Carina Nebula: the case of Trumpler 14

Beccari¹,

Marchi²,

Panagia³

et al. 2015

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We present a study of the mass accretion rates of pre-main sequence (PMS) stars in the cluster Trumpler 14 (Tr 14) in the Carina Nebula. Using optical multiband photometry we were able to identify 356 PMS stars showing Hα excess emission with equivalent width EW(Hα) > 20 Å. We interpret this observational feature as an indication that these objects are still actively accreting gas from their circumstellar medium. From a comparison of the HR diagram with PMS evolutionary models we derive ages and masses of the PMS stars. We find that most of the PMS objects are younger than 10 Myr with a median age of ∼3 Myr. Surprisingly, we also find that ∼20% of the mass accreting objects are older than 10 Myr. For each PMS star in Trumpler 14 we determine the mass accretion rate (Ṁ acc ) and discuss its dependence on mass and age. We finally combine the optical photometry with near-IR observations to build the spectral energy distribution (SED) for each PMS star in Tr 14. The analysis of the SEDs suggests the presence of transitional discs in which a large amount of gas is still present and sustains accretion onto the PMS object at ages older than 10 Myr. Our results, discussed in light of recent recent discoveries with Herschel of transitional discs containing a massive gas component around the relatively old PMS stars TW Hydrae, 49 Ceti, and HD 95086, support a new scenario n which old and evolved debris discs still host a significant amount of gas.

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Photometric determination of the mass accretion rates of pre-mainsequence stars - III. Results in the Large Magellanic Cloud

Cited by 40 publications

References 109 publications

TheHerschelGould Belt Survey in Chamaeleon II

TheHerschelGould Belt Survey in Chamaeleon II

Investigating the rotational evolution of young, low-mass stars using Monte Carlo simulations

Mass accretion rates from multiband photometry in the Carina Nebula: the case of Trumpler 14

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