Probing the Upper Scorpius mass function in the planetary-mass regime★

Lodieu, N.; Dobbie, P. D.; Cross, N. J. G.; Hambly, N. C.; Read, Mike; Blake, Robert; Floyd, David J. E.

doi:10.1093/mnras/stt1460

Cited by 24 publications

(29 citation statements)

References 81 publications

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“…A value of α ∼ 0.4 is also in line with previous determinations of the IMF in this region, e.g. , Lodieu et al (2013) find α = 0.45 ± 0.11. The right panel in Figure 8 which shows the samples without the HK cut again illustrates the effects of contamination on the mass function.…”

Section: Samplesupporting

confidence: 92%

“…VISTA) photometry so that we had sub-samples that had Z, Y, J, H, K photometry ('L-ZYJHK sample'); or had H and K photometry ('L-HK only sample'). We combined data from Dawson et al (2011), Lodieu et al (2011, Dawson et al (2013), Lodieu (2013), Lodieu et al (2013), and Dawson et al (2014) to obtain a sample of 789 unique objects, of which 493 were in the L-ZYJHK sample and 295 were in the L-HK only sample using photometry from both UKIDSS GCS DR10 (henceforth DR10) and the GCS Science verification release (henceforth SV; Dye et al 2006). Tables 7 and 8 give the full detail on how many objects were in each source catalog.…”

Section: The L-samplementioning

confidence: 99%

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Very Low-mass Stars and Brown Dwarfs in Upper Scorpius Using Gaia DR1: Mass Function, Disks, and Kinematics

Cook

Scholz

Jayawardhana

2017

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Our understanding of the brown dwarf population in star forming regions is dependent on knowing distances and proper motions, and therefore will be improved through the Gaia space mission. In this paper, we select new samples of very low mass objects (VLMOs) in Upper Scorpius using UKIDSS colors and optimised proper motions calculated using Gaia DR1. The scatter in proper motions from VLMOs in Upper Scorpius is now (for the first time) dominated by the kinematic spread of the region itself, not by the positional uncertainties. With age and mass estimates updated using Gaia parallaxes for early type stars in the same region, we determine masses for all VLMOs. Our final most complete sample includes 453 VLMOs of which ∼125 are expected to be brown dwarfs. The cleanest sample is comprised of 131 VLMOs, with ∼105 brown dwarfs. We also compile a joint sample from the literature which includes 415 VLMOs, out of which 152 are likely brown dwarfs. The disc fraction among low-mass brown dwarfs (M < 0.05 M ) is substantially higher than in more massive objects, indicating that discs around low-mass brown dwarfs survive longer than in lowmass stars overall. The mass function for 0.01 < M < 0.1 M is consistent with the Kroupa IMF. We investigate the possibility that some 'proper motion outliers' have undergone a dynamical ejection early in their evolution. Our analysis shows that the color-magnitude cuts used when selecting samples introduce strong bias into the population statistics due to varying level of contamination and completeness.

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Section: Samplesupporting

confidence: 92%

Section: The L-samplementioning

confidence: 99%

Very Low-mass Stars and Brown Dwarfs in Upper Scorpius Using Gaia DR1: Mass Function, Disks, and Kinematics

Cook

Scholz

Jayawardhana

2017

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“…The nine candidates from the top panel of Table 2 are indicated with red symbols and are labelled in all panels of the figure. We also included the known USco confirmed members and photometric candidates published by Ardila et al (2000), Lodieu et al (2011), and Lodieu et al (2013),…”

Section: Additional Photometric Criteriamentioning

confidence: 99%

A new free-floating planet in the Upper Scorpius association

Ramírez

Béjar

Osorio

2016

A&A

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We report on a deep photometric survey covering an area of 1.17 deg 2 in the young Upper Scorpius stellar association using VIMOS Iz and UKIDSS Z JHK data that was taken with several years in between. The search for the least massive population of Upper Scorpius (∼5-10 Myr, 145 pc) is performed on the basis of various optical and infrared color−color and color−magnitude diagrams, including WISE photometry, in the magnitude interval J = 14.5−19 mag (completeness), which corresponds to substellar masses from 0.028 through 0.004 M at the age and distance of Upper Scorpius. We also present the proper motion analysis of the photometric candidates, finding that two objects successfully pass all photometric and astrometric criteria for membership in the young stellar association. One of them, USco J155150.2−213457, is a new discovery. We obtained low resolution, near-infrared spectroscopy (R ∼ 450, 0.85-2.35 µm) of this new finding using the FIRE instrument. We confirmed its low-gravity atmosphere expected for an Upper Scorpius member (weak alkaline lines, strong VO absorption, peaked H-band pseudocontinuum). By comparison with spectroscopic standards, we derive a spectral type of L6 ± 1, and estimate a mass of ≈0.008-0.010 M for USco J155150.2−213457. The colors and spectral slope of this object resemble those of other young, cool members of Upper Scorpius and σ Orionis (∼3 Myr) and field, high gravity dwarfs of related classification in contrast with the very red indices of field, low gravity, L-type dwarfs of intermediate age. USco J155150.2−213457, which does not show infrared flux excesses up to 4.5 µm, becomes one of the least massive and latest type objects known in the entire Upper Scorpius stellar association.

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“…Our catalog comprises the largest set of proper motions for low-mass (spectral types M3) members of Upper Sco published to date. It includes 40 objects for which no proper motion has previously been published and 266 that improve on existing literature values, which were drawn from NOMAD (Zacharias et al 2005), PPMXL (Roeser et al 2010), SDSS DR9 (Ahn et al 2012), UCAC4 (Zacharias et al 2013), UKIDSS GCS DR9 (Lawrence et al 2013), USNO-B (Monet et al 2003), Dawson et al (2011);Lodieu et al (2007Lodieu et al ( , 2013, and Lodieu (2013). We list our proper motions, number of epochs used, reduced c 2 , and time baseline for each proper motion fit in Table 9.…”

Section: Appendix B Proper Motions Of Known Upper Scorpius Membersmentioning

confidence: 99%

A Search for L/T Transition Dwarfs with Pan-STARRS1 and WISE. III. Young L Dwarf Discoveries and Proper Motion Catalogs in Taurus and Scorpius–Centaurus

Best

Liu

Magnier

et al. 2017

ApJ

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We present the discovery of eight young M7-L2 dwarfs in the Taurus star-forming region and the ScorpiusCentaurus OB Association, serendipitously found during a wide-field search for L/T transition dwarfs using Pan-STARRS1 (optical) and WISE (mid-infrared) photometry. We identify PSOJ060.3200+25.9644 (near-infrared spectral type L1) and PSOJ077.1033+24.3809 (L2) as new members of Taurus based on their VL-G gravity classifications, the consistency of their photometry and proper motions with previously known Taurus objects, and the low probability of contamination by field objects. PSOJ077.1033+24.3809 is the coolest substellar member of Taurus found to date. Both Taurus objects are among the lowest-mass free-floating objects ever discovered, with estimated masses ≈6M Jup , and provide further evidence that isolated planetary-mass objects can form as part of normal star formation processes. PSOJ060.3200+25.9644 (a.k.a. DANCe J040116.80+255752.2) was previously identified as a likely member of the Pleiades (age » 125 Myr) based on photometry and astrometry, but its VL-G gravity classification and near-infrared photometry imply a much younger age and thus point to Taurus membership. We have also discovered six M7-L1 dwarfs in outlying regions of Scorpius-Centaurus with photometry, proper motions, and low-gravity spectral signatures consistent with membership. These objects have estimated masses ≈15-36M Jup . The M7 dwarf, PSOJ237.1470−23.1489, shows excess mid-infrared flux implying the presence of a circumstellar disk. Finally, we present catalogs of Pan-STARRS1 proper motions for low-mass members of Taurus and Upper Scorpius with median precisions of ≈3 mas yr −1 , including 67 objects with no previous proper motion and 359 measurements that improve on literature values.

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Probing the Upper Scorpius mass function in the planetary-mass regime★

Cited by 24 publications

References 81 publications

Very Low-mass Stars and Brown Dwarfs in Upper Scorpius Using Gaia DR1: Mass Function, Disks, and Kinematics

Very Low-mass Stars and Brown Dwarfs in Upper Scorpius Using Gaia DR1: Mass Function, Disks, and Kinematics

A new free-floating planet in the Upper Scorpius association

A Search for L/T Transition Dwarfs with Pan-STARRS1 and WISE. III. Young L Dwarf Discoveries and Proper Motion Catalogs in Taurus and Scorpius–Centaurus

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