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J/AJ/154/256      VLM stars and BDs in Upper Sco using Gaia DR1    (Cook+, 2017)

Very low-mass stars and brown dwarfs in Upper Scorpius using Gaia DR1: mass function, disks, and kinematics. Cook N.J., Scholz A., Jayawardhana R. <Astron. J., 154, 256-256 (2017)> =2017AJ....154..256C (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; Photometry, infrared ; Proper motions Keywords: brown dwarfs - stars: luminosity function, mass function - open clusters and associations: individual: Upper Sco - stars: low-mass Abstract: 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 optimized 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 that includes 415 VLMOs, out of which 152 are likely brown dwarfs. The disk fraction among low-mass brown dwarfs (M<0.05M) is substantially higher than in more massive objects, indicating that disks around low-mass brown dwarfs survive longer than in low-mass stars overall. The mass function for 0.01<M<0.1M is consistent with the Kroupa Initial Mass Function. 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 levels of contamination and completeness. 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 optimized 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 that includes 415 VLMOs, out of which 152 are likely brown dwarfs. The disk fraction among low-mass brown dwarfs (M<0.05M) is substantially higher than in more massive objects, indicating that disks around low-mass brown dwarfs survive longer than in low-mass stars overall. The mass function for 0.01<M<0.1M is consistent with the Kroupa Initial Mass Function. 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 levels of contamination and completeness. Description: We used literature samples (Dawson et al. (2011MNRAS.418.1231D, Cat. J/MNRAS/418/1231), Lodieu et al. (2011MNRAS.418.2604L), Dawson et al. (2013MNRAS.429..903D, Cat. J/MNRAS/429/903), Lodieu (2013MNRAS.431.3222L, Cat. J/MNRAS/431/3222), Lodieu (2013MNRAS.435.2474L, Cat. J/MNRAS/435/2474) and Dawson et al. (2014MNRAS.442.1586D)) and UKIDSS photometric data (Lawrence et al. (2007MNRAS.379.1599L, Cat. II/314) along with new proper motion data (using data from Gaia DR1 i.e. Altmann et al. (2017A&A...600L...4A, Cat. I/339), Tian et al. (2017ApJS..232....4T)) to construct catalogues of objects in Upper Scorpius. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table9a.dat 458 68 C sample sources with ZYJHK photometry from the DR10 and Red HK (C-ZYJHKDR10Red_HK) table9b.dat 458 224 C sample sources with ZYJHK photometry from the DR10 and Red no HK (C-ZYJHKDR10Red_noHK) table9c.dat 458 49 C sample sources with ZYJHK photometry from the DR10 no Red HK (C-ZYJHKDR10noRed_HK) table9d.dat 458 171 C sample sources with ZYJHK photometry from the DR10 no Red no HK (C-ZYJHKDR10noRed_noHK) table9e.dat 458 14 C sample sources with ZYJHK photometry from the SV and HK (C-ZYJHKSVHK) table9f.dat 458 58 C sample sources with ZYJHK photometry from the SV and no HK (C-ZYJHKSVnoHK) table10a.dat 496 175 L sample sources with only H and K photometry (L-HKonly) table10b.dat 496 415 L sample sources with ZYJHK photometry (L-ZYJHK)
See also: I/339 : Hot Stuff for One Year (HSOY) (Altmann+, 2017) II/314 : UKIDSS-DR8 LAS, GCS and DXS Surveys (Lawrence+ 2012) J/MNRAS/418/1231 : New brown dwarfs in upper Sco (Dawson+, 2011) J/MNRAS/429/903 : New brown dwarf discs in Upper Scorpius (Dawson+, 2013) J/MNRAS/431/3222 : UKIDSS GCS Upper Sco members (Lodieu, 2013) J/MNRAS/435/2474 : USco ZYJHK1K2 photometry and proper motions (Lodieu+, 2013) Byte-by-byte Description of file: table9?.dat
Bytes Format Units Label Explanations
1- 12 I12 --- UID Unique identifier (1) 14- 27 F14.10 deg RAdeg Right Ascension in decimal degrees (J2000) 29- 42 F14.10 deg DEdeg Declination in decimal degrees (J2000) 44- 61 F18.15 mag Zmag UKIDSS Z magnitude 63- 83 F21.19 mag e_Zmag Uncertainty in Zmag 85-102 F18.15 mag Ymag UKIDSS Y magnitude 104-124 F21.19 mag e_Ymag Uncertainty in Ymag 126-143 F18.15 mag Jmag UKIDSS J magnitude 145-165 F21.19 mag e_Jmag Uncertainty in Jmag 167-184 F18.15 mag Hmag UKIDSS H magnitude 186-206 F21.19 mag e_Hmag Uncertainty in Hmag 208-225 F18.15 mag Kmag K magnitude 227-248 F22.20 mag e_Kmag Uncertainty in Kmag 250-257 F8.5 mas/yr pm Most precise proper motion 259-265 F7.5 mas/yr e_pm Uncertainty in pm 267-270 A4 --- r_pm Reference for pm (2) 272-280 F9.5 mas/yr pmRA Most precise proper motion in RA 282-288 F7.5 mas/yr e_pmRA Uncertainty in pmRA 290-298 F9.5 mas/yr pmDE Most precise proper motion in DE 300-306 F7.5 mas/yr e_pmDE Uncertainty in pmDE 308 I1 --- WISE Has WISE photometry (3) 310 I1 --- Disk Flagged as having a disc (4) 312-316 F5.3 solMass MassFit Best χ2 fit for mass 318-322 F5.3 solMass bMassFit Lower Uncertainty bound in MassFit 324-328 F5.3 solMass BMassFit Upper Uncertainty bound in MassFit 330-335 F6.1 K TeffFit Best χ2 fit for effective temperature 337-341 F5.1 K bTeffFit Lower Uncertainty bound in TeffFit 343-347 F5.1 K BTeffFit Upper Uncertainty bound in TeffFit 349-353 F5.2 solLum LumFit Best χ2 fit for luminosity 355-359 F5.2 solLum bLumFit Lower Uncertainty bound in LumFit 361-365 F5.2 solLum BLumFit Upper Uncertainty bound in LumFit 367-370 F4.2 [cm/s2] loggFit Best χ2 fit for surface gravity 372-375 F4.2 [cm/s2] bloggFit Lower Uncertainty bound in loggFit 377-380 F4.2 [cm/s2] BloggFit Upper Uncertainty bound in loggFit 382-386 F5.3 solRad RadFit Best χ2 fit for radius 388-392 F5.3 solRad bRadFit Lower Uncertainty bound in RadFit 394-398 F5.3 solRad BRadFit Upper Uncertainty bound in RadFit 400-410 F11.5 --- chilow Low fit χ2 412-422 F11.5 --- chimid Mid fit χ2 424-434 F11.5 --- chihi High fit χ2 436 I1 --- Wise+Mass Has WISE photometry and a mass estimate 438-445 F8.5 --- sigExpmRA Sigma excess in pmRA 447-454 F8.5 --- sigExpmDE Sigma excess in pmDE 456 I1 --- fnpmout Not an outlier in pm; 2σ (3) 458 I1 --- fpmout Is an outlier in pm; 2σ (3)
Note (1): Of this merged detection as assigned by merge algorithm. ID is unique over entire WSA via program ID prefix. Note (2): Reference for pm as follows: hsoy = Hot Stuff for One Year (HSOY) catalog (Altmann et al., 2017A&A...600L...4A, Cat. I/339) gps1 = Gaia-PS1-SDSS (GPS1) catalog (Tian et al., 2017ApJS..232....4T) gcs = The UKIRT Infrared Deep Sky Survey (UKIDSS) catalog (Lawrence et al., 2007MNRAS.379.1599L, Cat. II/314) ucac = UCAC5: New Proper Motions Using Gaia DR1 catalog (Zacharias et al., 2017AJ....153..166Z, Cat. I/340) Note (3): Flag as follows: 1 = true; 0 = false. Note (4): Dawson et al. (2013MNRAS.429..903D, Cat. J/MNRAS/429/903) WISE W1-W2 or WISE W3 disc. Flag as follows: 1 = true; 0 = false.
Byte-by-byte Description of file: table10[ab].dat
Bytes Format Units Label Explanations
1- 8 A8 --- UID Unique ID from catalog creation 10- 23 F14.10 deg RAdeg Right Ascension in decimal degrees (J2000) 25- 38 F14.10 deg DEdeg Declination in decimal degrees (J2000) 40- 46 A7 --- Coord Source of main coordinates 48- 92 A45 --- Cat Catalog contained in (1) 94-101 F8.5 mag Zmag ? Most precise Z magnitude 103-118 A16 --- r_Zmag Reference for Zmag (1) 120-126 F7.5 mag e_Zmag ? Uncertainty in Zmag 128-135 F8.5 mag Ymag ? Most precise Y magnitude 137-152 A16 --- r_Ymag Reference for Ymag (1) 154-160 F7.5 mag e_Ymag ? Uncertainty in Ymag 162-169 F8.5 mag Jmag ? Most precise J magnitude 171-186 A16 --- r_Jmag Reference for Jmag (1) 188-194 F7.5 mag e_Jmag ? Uncertainty in Jmag 196-203 F8.5 mag Hmag Most precise H magnitude 205-220 A16 --- r_Hmag Reference for Hmag (1) 222-228 F7.5 mag e_Hmag Uncertainty in Hmag 230-237 F8.5 mag Kmag Most precise K magnitude 239-254 A16 --- r_Kmag Reference for Kmag (1) 256-262 F7.5 mag e_Kmag Uncertainty in Kmag 264-267 A4 --- SpTCat Spetral type from source catalog 269-272 A4 --- r_SpTCat Reference for SpTcat (1) 274-279 A6 solMass MassCat Mass from source catalog 281-284 A4 --- r_MassCat Reference for MassCat (1) 286 I1 --- fZYJHK Flag whether source has valid ZYJHK photometry (2) 288 I1 --- fHKonly Flag that source only has HK photometry (2) 290-297 F8.5 mas/yr pm Most precise proper motion 299-305 F7.5 mas/yr e_pm Uncertainty in pm 307-310 A4 --- r_pm Reference for pm (3) 312-320 F9.5 mas/yr pmRA Most precise proper motion in RA 322-328 F7.5 mas/yr e_pmRA Uncertainty in pmRA 330-338 F9.5 mas/yr pmDE Most precise proper motion in DE 340-346 F7.5 mas/yr e_pmDE Uncertainty in pmDE 348-352 F5.3 solMass MassFit ? Best χ2 fit for mass 354-358 F5.3 solMass bMassFit ? Lower Uncertainty bound in MassFit 360-364 F5.3 solMass BMassFit ? Upper Uncertainty bound in MassFit 366-371 F6.1 K TeffFit ? Best χ2 fit for effective temperature 373-377 F5.1 K bTeffFit ? Lower Uncertainty bound in TeffFit 379-383 F5.1 K BTeffFit ? Upper Uncertainty bound in TeffFit 385-389 F5.2 solLum LumFit ? Best χ2 fit for luminosity 391-395 F5.2 solLum bLumFit ? Lower Uncertainty bound in LumFit 397-401 F5.2 solLum BLumFit ? Upper Uncertainty bound in LumFit 403-406 F4.2 [cm/s2] loggFit ? Best χ2 fit for surface gravity 408-411 F4.2 [cm/s2] bloggFit ? Lower Uncertainty bound in loggFit 413-416 F4.2 [cm/s2] BloggFit ? Upper Uncertainty bound in loggFit 418-422 F5.3 solRad RadFit ? Best χ2 fit for radius 424-428 F5.3 solRad bRadFit ? Lower Uncertainty bound in RadFit 430-434 F5.3 solRad BRadFit ? Upper Uncertainty bound in RadFit 436-446 F11.5 --- chilow ? Low fit χ2 448-458 F11.5 --- chimid ? Mid fit χ2 460-470 F11.5 --- chihi ? High fit χ2 472 I1 --- Disk Flagged as having a disc (4) 474 I1 --- Wise+Mass Has WISE photometry and a mass estimate (2) 476-483 F8.5 --- sigExpmRA Sigma excess in pmRA 485-492 F8.5 --- sigExpmDE Sigma excess in pmDE 494 I1 --- fnpmout Not an outlier in pm; 2σ (2) 496 I1 --- fpmout Is an outlier in pm; 2σ (2)
Note (1): Reference for MassCat as follows: GCSSV = From UKIDSS Science verification (Lawrence et al., 2007MNRAS.379.1599L, Cat. Cat. II/314]) GCSDR10 = From UKIDSS DR10 (Lawrence et al. 2007MNRAS.379.1599L, Cat. II/314) D11 = From Dawson et al., 2011MNRAS.418.1231D, Cat. J/MNRAS/418/1231 L11 = From Lodieu et al., 2011MNRAS.418.2604L] D13 = From Dawson et al., 2013MNRAS.429..903D, Cat. J/MNRAS/429/903 L13a = From Lodieu, 2013MNRAS.431.3222L, Cat. J/MNRAS/431/3222 L13a_HK from HK sample, L13aZYJHKSV from the ZYJHK UKIDSS Science verification sample, L13aZYJHKred from the ZYJHK UKIDSS DR10 affected by reddening sample, L13aZYJHKnored from the ZYJHK UKIDSS DR10 devoid of reddening sample L13b = From Lodieu, 2013MNRAS.435.2474L, Cat. J/MNRAS/435/2474 D14 = From Dawson et al., 2014MNRAS.442.1586D Note (2): Flag as follows: 1 = true; 0 = false. Note (3): Reference for pm as follows: hsoy = Hot Stuff for One Year (HSOY) catalog (Altmann et al., 2017A&A...600L...4A, Cat. I/339) gps1 = Gaia-PS1-SDSS (GPS1) catalog (Tian et al., 2017ApJS..232....4T) gcs = The UKIRT Infrared Deep Sky Survey (UKIDSS) catalog (Lawrence et al., 2007MNRAS.379.1599L, Cat. II/314) Note (4): From isochrones (i.e have ZYJHKW1W2 photometry). Flag as follows: 1 = true; 0 = false.
History: Corrected version from author. Acknowledgements: Neil James, neil.james.cook(at)gmail.com
(End) Patricia Vannier [CDS] 10-Apr-2018
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