Further mid-infrared study of the rho Ophiuchi cloud young stellar population: Luminosities and masses of pre-main-sequence stars

Greene, Thomas P.; Wilking, B. A.; André, P.; Young, Erick T.; Lada, Charles J.

doi:10.1086/174763

Cited by 453 publications

(615 citation statements)

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“…In this section, and in light of the newly discovered substellar members in our survey, we use SEDs to classify the evolutionary state of each object. The slope of the SED (α = ∂log(λF λ )/∂log(λ)) is used to distinguish YSOs into various classes according to their mid-IR (and millimetre) emitting energy (Lada & Wilking 1984;Adams et al 1987;Lada 1987), representing deeply embedded YSOs (Class 0, Andre et al 1993), embedded YSOs still surrounded by an envelope (Class I), YSOs possessing a circumstellar disk (Class II), flat-spectrum sources which may represent an intermediate stage between Class I and II (FS, Greene et al 1994), and sources with a weak or debris disk (Class III).…”

Section: Slopes Of the Spectral Energy Distributionsmentioning

confidence: 99%

Spectroscopy of new brown dwarf members ofρ Ophiuchi and an updated initial mass function

Oliveira¹,

Moraux²,

Bouvier³

et al. 2012

A&A

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Aims. To investigate the universality hypothesis of the initial mass function in the substellar regime, the population of the ρ Ophiuchi molecular cloud is analysed by including a new sample of low-mass spectroscopically confirmed members. To that end, we have conducted a large spectroscopic follow-up of young substellar candidates uncovered in our previous photometric survey. Methods. The spectral types and extinction were derived for a newly found population of substellar objects, and its masses estimated by comparison to evolutionary models. A thoroughly literature search was conducted to provide an up-to-date census of the cluster, which was then used to derive the luminosity and mass functions, as well as the ratio of brown dwarfs to stars in the cluster. These results were then compared to other young clusters. Results. It is shown that the study of the substellar population of the ρ Ophiuchi molecular cloud is hampered only by the high extinction in the cluster ruling out an apparent paucity of brown dwarfs. The discovery of 16 new members of ρ Ophiuchi, 13 of them in the substellar regime, reveals the low-mass end of its population and shows the success of our photometric candidate selection with the WIRCam survey. The study of the brown dwarf population of the cluster reveals a high disk fraction of 76 +5 −8 %. Conclusions. Taking the characteristic peak mass of the derived mass function and the ratio of brown dwarfs to stars into account, we conclude that the mass function of ρ Ophiuchi is similar to other nearby young clusters.

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Section: Slopes Of the Spectral Energy Distributionsmentioning

confidence: 99%

Spectroscopy of new brown dwarf members ofρ Ophiuchi and an updated initial mass function

Oliveira¹,

Moraux²,

Bouvier³

et al. 2012

A&A

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“…With all three J, H and K filters, we obtained a sequence of 10 × 1.18 s exposures using a random jittering pattern in a 20 × 20 box. Bontemps et al (2001), while the near-infrared magnitudes are from Barsony et al (1997), Greene et al (1994) and the 2MASS database (2MASS uses a Ks filter rather than a K filter; the difference in magnitude for an object can reach a few tenths of a magnitude). The source marked with a † symbol has an infrared spectral index typical of a normal Class II source but Ressler & Barsony (2001) have shown that this system contains a Class I source and it is classified as such here.…”

Section: Sample Selection and Observationsmentioning

confidence: 99%

Multiple protostellar systems

Duchêne

Bouvier²,

Bontemps

et al. 2004

A&A

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Abstract. We performed a deep infrared imaging survey of 63 embedded young stellar objects (YSOs) located in the Taurus and Ophiuchus clouds to search for companions. The sample includes Class I and flat infrared spectrum protostellar objects. We find 17 companions physically bound to 15 YSOs with angular separations in the range 0.8-10 (110-1400 AU) and derive a companion star fraction of 23 ± 9% and 29 ± 7% for embedded YSOs in Taurus and Ophiuchus, respectively, about twice as large as that found among G dwarfs in the solar neighborhood. Therefore, binary and multiple protostellar systems are a very frequent outcome of the fragmentation of prestellar cores. In spite of different properties of the clouds and especially of the prestellar cores, the fraction of wide companions, 27 ± 6% for the combined sample, is identical in the two star-forming regions. This suggests that the frequency and properties of wide multiple protostellar systems are not very sensitive to specific initial conditions. Comparing the companion star fraction of the youngest YSOs still surrounded by extended envelopes to that of more evolved YSOs, we find evidence for a possible evolution of the fraction of wide multiple systems, which seems to decrease by a factor of about two on a timescale of ∼10 5 yr. For the first time it is possible to confront the result of a multiplicity survey of a nearly complete population of embedded YSOs at an age of ∼10 5 yr to numerical simulations of molecular cloud collapse which, after a few free fall times, reach this evolutionary stage. Somewhat contrary to model predictions, we do not find evidence for a sub-clustering of embedded sources at this stage on a scale of a few 100 AU that could be related to the formation of small-N protostellar clusters. Possible interpretations of this discrepancy are discussed.

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“…Equivalently, class I YSOs have α > 0, class II have −3 < α < 0 and class III α ∼ −3, using the conventional definition of spectral class (Lada 1987), although more recent studies (e.g. André & Montmerle 1994;Greene et al 1994) have found that the class II/III border lies at a higher value (α −1.5). Where previous K-band data exist in the literature the wavelengths were taken as λ 2 = 14.0 µm (our data) and λ 1 = 2.2 µm (K-band data from references in Table 1) and this was applied to both the observed spectrum and the calculated continuum for each source.…”

Section: Spectral Indexmentioning

confidence: 99%

ISOCAM-CVF spectroscopy of the circumstellar environment of young stellar objects

Alexander

Casali

André

et al. 2003

A&A

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Abstract. We present the results of a mid-infrared (5-16.5 µm) imaging spectroscopy survey of Young Stellar Objects (YSOs) and their surrounding environment in four low-mass star formation regions: RCrA, ρ Ophiuchi, Serpens and Chamaeleon I. This survey was performed using ISOCAM and its Circular Variable Filters (CVF) and observed 42 YSO candidates: we were able to obtain complete 5-16.5 µm spectra for 40 of these with a spectral resolving power of λ/∆λ 40. A number of spectral features were measured, most notably the 9.7 µm silicate feature, the bending modes of both water and CO 2 ices at 6.0 and 15.2 µm respectively and the well-known unidentified feature at 6.8 µm. The strength of the unidentified feature was observed to correlate very well with that of the water ice bending mode and far less strongly with the CO 2 ice bending mode. This suggests, in a manner consistent with previous observations, that the carrier of the unidentified feature is a strongly polar ice. Absorption profiles of the bending mode of CO 2 ice are observed to show a significant long wavelength wing, which suggests that a significant fraction of the CO 2 ice observed exists in a polar (H 2 O-rich) phase. The sources observed in RCrA, ρ Oph and Serpens show similar spectral characteristics, whilst the sources observed in Cha I are somewhat anomalous, predominantly showing silicate emission and little or no absorption due to volatile ices. However this is consistent with previous studies of this region of the Cha I cloud, which contains an unusual cluster of YSOs. From comparisons of the strengths of the water ice and silicate bands we detect an apparent under-abundance of water ice towards the sources in ρ Oph, relative to both RCrA and Serpens. This may be indicative of differences in chemical composition between the different clouds, or may be due to evaporation. Finally the CO 2 :H 2 O ice ratios observed towards the sources in ρ Oph show significantly greater scatter than in the other regions, possibly due to varying local conditions around the YSOs in ρ Oph.

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Further mid-infrared study of the rho Ophiuchi cloud young stellar population: Luminosities and masses of pre-main-sequence stars

Cited by 453 publications

References 0 publications

Spectroscopy of new brown dwarf members ofρ Ophiuchi and an updated initial mass function

Spectroscopy of new brown dwarf members ofρ Ophiuchi and an updated initial mass function

Multiple protostellar systems

ISOCAM-CVF spectroscopy of the circumstellar environment of young stellar objects

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