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 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 2011MNRAS.418.1231D, Cat.
J/MNRAS/418/1231), Lodieu et al. (2011MNRAS.418.2604L 2011MNRAS.418.2604L), Dawson et al.
(2013MNRAS.429..903D 2013MNRAS.429..903D, Cat. J/MNRAS/429/903), Lodieu
(2013MNRAS.431.3222L 2013MNRAS.431.3222L, Cat. J/MNRAS/431/3222), Lodieu
(2013MNRAS.435.2474L 2013MNRAS.435.2474L, Cat. J/MNRAS/435/2474) and Dawson et al.
(2014MNRAS.442.1586D 2014MNRAS.442.1586D)) and UKIDSS photometric data (Lawrence et al.
(2007MNRAS.379.1599L 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 2017A&A...600L...4A,
Cat. I/339), Tian et al. (2017ApJS..232....4T 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 2017A&A...600L...4A, Cat. I/339)
gps1 = Gaia-PS1-SDSS (GPS1) catalog (Tian et al., 2017ApJS..232....4T 2017ApJS..232....4T)
gcs = The UKIRT Infrared Deep Sky Survey (UKIDSS) catalog (Lawrence et al.,
2007MNRAS.379.1599L 2007MNRAS.379.1599L, Cat. II/314)
ucac = UCAC5: New Proper Motions Using Gaia DR1 catalog (Zacharias et al.,
2017AJ....153..166Z 2017AJ....153..166Z, Cat. I/340)
Note (3): Flag as follows:
1 = true;
0 = false.
Note (4): Dawson et al. (2013MNRAS.429..903D 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 2007MNRAS.379.1599L, Cat. Cat. II/314])
GCSDR10 = From UKIDSS DR10 (Lawrence et al. 2007MNRAS.379.1599L 2007MNRAS.379.1599L, Cat. II/314)
D11 = From Dawson et al., 2011MNRAS.418.1231D 2011MNRAS.418.1231D, Cat. J/MNRAS/418/1231
L11 = From Lodieu et al., 2011MNRAS.418.2604L 2011MNRAS.418.2604L]
D13 = From Dawson et al., 2013MNRAS.429..903D 2013MNRAS.429..903D, Cat. J/MNRAS/429/903
L13a = From Lodieu, 2013MNRAS.431.3222L 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 2013MNRAS.435.2474L, Cat. J/MNRAS/435/2474
D14 = From Dawson et al., 2014MNRAS.442.1586D 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 2017A&A...600L...4A, Cat. I/339)
gps1 = Gaia-PS1-SDSS (GPS1) catalog (Tian et al., 2017ApJS..232....4T 2017ApJS..232....4T)
gcs = The UKIRT Infrared Deep Sky Survey (UKIDSS) catalog (Lawrence et al.,
2007MNRAS.379.1599L 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