Contamination by field late-M, L, and T dwarfs in deep surveys

Caballero, J. A.; Burgasser, Adam J.; Klement, Rainer J.

doi:10.1051/0004-6361:200809520

Cited by 70 publications

(116 citation statements)

References 123 publications

(201 reference statements)

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“…The solid line represents the spectrophotometric sequence of field mid-M-to late-T-type dwarfs, shifted to match the brightness of the late-M-type cluster members (Zapatero Osorio et al 2008). For the field dwarfs, we use average absolute I-band magnitudes, I − J, and J − K s colours compiled by Caballero et al (2008a) 6 , J − H colours from Vrba et al (2004) 7 , and mid-infrared magnitudes from Patten et al (2006). In Fig.…”

Section: Resultsmentioning

confidence: 99%

“…This predicted value remains mostly indicative, because the initial mass function and scale heights of late L-and T-type dwarfs are still uncertain. Interestingly, Caballero et al (2008a) assume a rising mass function in the planetary mass regime and predict spatial densities of T0-8 dwarfs that are a factor of two higher than those derived from observations (Metchev et al 2008;Lodieu et al 2009a). …”

Section: Cluster Membershipmentioning

confidence: 90%

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Candidate free-floating super-Jupiters in the young σ Orionis open cluster

Bihain

Rebolo

Osorio³

et al. 2009

A&A

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Context. Free-floating substellar candidates with estimated theoretical masses of as low as ∼5 Jupiter masses have been found in the ∼3 Myr old σ Orionis open cluster. As the overlap with the planetary mass domain increases, the question of how these objects form becomes important. The determination of their number density and whether a mass cut-off limit exists is crucial to understanding their formation. Aims. We propose to search for objects of yet lower masses in the cluster and determine the shape of the mass function at low mass. Methods. Using new-and (re-analysed) published IZJHK s [3.6]−[8.0]-band data of an area of 840 arcmin 2 , we performed a search for LT-type cluster member candidates in the magnitude range J = 19.5-21.5 mag, based on their expected magnitudes and colours. Results. Besides recovering the T type object S Ori 70 and two other known objects, we find three new cluster member candidates, S Ori 72-74, with J ≈ 21 mag and within 12 arcmin of the cluster centre. They have theoretical masses of 4 +3 −2 M Jup and are among the least massive free-floating objects detected by direct imaging outside the Solar System. The photometry in archival Spitzer [3.6]-[5.8]-band images infers that S Ori 72 is an L/T transition candidate and S Ori 73 a T-type candidate, following the expected cluster sequence in the mid-infrared. Finally, the L-type candidate S Ori 74 with lower quality photometry is located at 11.8 arcsec (∼4250 AU) of a stellar member of σ Orionis and could be a companion. After contaminant correction in the area complete to J = 21.1 mag, we estimate that there remain between zero and two cluster members in the mass interval 6-4 M Jup . Conclusions. We present S Ori 73, a new candidate T type and candidate σ Orionis member of a few Jupiter masses. Our result suggests a possible turnover in the substellar mass spectrum below ∼6 Jupiter masses, which could be investigated further by wider and deeper photometric surveys.

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Section: Resultsmentioning

confidence: 99%

Section: Cluster Membershipmentioning

confidence: 90%

Candidate free-floating super-Jupiters in the young σ Orionis open cluster

Bihain

Rebolo

Osorio³

et al. 2009

A&A

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“…As shown by Caballero et al (2008), the field population of very cool stars at faint magnitudes can easily dominate the members of the same temperature in young aggregates. The estimate of the expected number of cool field objects in the images presented here is made somewhat difficult by the irregular extinction across the Lupus 3 field, which in turn makes the distance up to which objects would be detected dependent on the direction.…”

Section: Field Populationmentioning

confidence: 91%

No substellar objects at the center of the Lupus 3 star-forming cloud

Comerón¹

2011

A&A

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Context. Current surveys of nearby star-forming regions and young aggregates that produce samples of objects spanning the entire mass range down to masses of a few Jupiter masses can address questions about differences in the substellar mass function among different regions and the lowest masses of objects that can form in isolation. Aims. Deep imaging of a selected area in the Lupus 3 star-forming region, characterized by a large number of known young stellar objects, has been carried out with the goal of producing a complete sampling of the mass function down to sub-Jupiter masses. Methods. I C JHK S imaging complemented with intermediate-band imaging sensitive to methane absorption has been obtained with the VLT. The observed area measures 7 3 × 7 4 (0.42 × 0.43 pc 2 at 200 pc) and the background is obscured by A V < 5 mag in approximately 70% of it. Detection limits (3σ) are I C = 25.6, J = 23.1, H = 22.3, and K S = 21.3. Cool objects with temperatures below 3000 K are identified by means of reddening-free indices. Objects cooler than ∼1300 K should also be detectable by comparing the flux in the H and methane-continuum bands.Results. The luminosities of the 17 identified cool objects are too low in all cases to be consistent with membership in the star-forming region. Their number agrees with the statistical expectation for the background population of very low-mass stars. A reexamination of known candidate young stellar objects leads to excluding eight of them, reducing the number of bona fide members in the area to 15, of which ten lie in low extinction regions. The expectation based on the stars-to-brown dwarf ratios derived in other young aggregates is to find two or three new brown dwarfs, whereas none have been found. The low-mass young stellar object Par-Lup3-3 is found to consist of two close components of similar brightness separated by 0 3. A very faint object is also detected 1 2 from the jet-driving very low-mass star Par-Lup3-4 that, if confirmed as a physical companion, would have an estimated mass of 1−2 M Jup . Conclusions. The absence of brown dwarfs in one of the most crowded areas of the Lupus 3 clouds, although limited by small-number statistics, argues against a mass function rich in very low-mass objects, as might have been expected if the apparent overabundance of mid-M spectral types in Lupus extended toward later types. The results also stress the importance of critically examining the actual nature of previously identified candidate young stellar objects at the time of drawing statistical conclusions about the substellar population.

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“…In a second step, we used the space density of M dwarfs (≈ 5.4x10 −2 pc −3 , from Caballero et al 2008 and reference therein), to estimate the likelihood of a close proximity in space by chance. Taking into account the distances and the separations of our system, we calculated a volume for each target.…”

Section: Chance Alignmentsmentioning

confidence: 99%

Discovery of wide low and very low-mass binary systems using Virtual Observatory tools

Gálvez-Ortiz

Solano

Lodieu

et al. 2016

Mon. Not. R. Astron. Soc.

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The frequency of multiple systems and their properties are key constraints of stellar formation and evolution. Formation mechanisms of very low-mass (VLM) objects are still under considerable debate and an accurate assessment of their multiplicity and orbital properties are essential for constraining current theoretical models.Taking advantage of the Virtual Observatory capabilities, we looked for comoving low and VLM binary (or multiple) systems using the Large Area Survey of the UKIDSS LAS DR10, SDSS DR9, and the 2MASS Catalogues. Other catalogues (W ISE, GLIMPSE, SuperCosmos ...) were used to derive the physical parameters of the systems.We report the identification of 36 low and VLM (∼M0-L0 spectral types) candidates to binary/multiple system (separations between 200 and 92000 AU), whose physical association is confirmed through common proper motion, distance and low probability of chance alignment. This new system list notably increases the previous sampling in their mass-separation parameter space (∼100). We have also found 50 low-mass objects that we can classify as ∼L0-T2 according to their photometric information. Only one of these objects presents a common proper motion high-mass companion.Although we could not constrain the age of the majority of the candidates, probably most of them are still bound except four that may be under disruption processes. We suggest that our sample could be divided in two populations: one tightly bound wide VLM systems that are expected to last more than 10 Gyr, and other formed by weak bound wide VLM systems that will dissipate within a few Gyrs.

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Contamination by field late-M, L, and T dwarfs in deep surveys

Cited by 70 publications

References 123 publications

Candidate free-floating super-Jupiters in the young σ Orionis open cluster

Candidate free-floating super-Jupiters in the young σ Orionis open cluster

No substellar objects at the center of the Lupus 3 star-forming cloud

Discovery of wide low and very low-mass binary systems using Virtual Observatory tools

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