J/AJ/154/46 Proper motions and photometry for members of Cha I (Esplin+, 2017)
A survey for planetary-mass brown dwarfs in the Chamaeleon I star-forming
region.
Esplin T.L., Luhman K.L., Faherty J.K., Mamajek E.E., Bochanski J.J.
<Astron. J., 154, 46-46 (2017)>
=2017AJ....154...46E 2017AJ....154...46E (SIMBAD/NED BibCode)
ADC_Keywords: Associations, stellar ; Stars, dwarfs ; Spectral types ;
Proper motions ; Extinction ; Photometry, infrared
Keywords: brown dwarfs - planetary systems - protoplanetary disks -
stars: formation - stars: low-mass -
stars: luminosity function, mass function - stars: pre-main sequence
Abstract:
We have performed a search for planetary-mass brown dwarfs in the
Chamaeleon I star-forming region using proper motions and photometry
measured from optical and infrared images from the Spitzer Space
Telescope, the Hubble Space Telescope, and ground-based facilities.
Through near-IR spectroscopy at Gemini Observatory, we have confirmed
six of the candidates as new late-type members of Chamaeleon I
(≥M8). One of these objects, ChaJ11110675-7636030, has the faintest
extinction-corrected MK among known members, which corresponds to a
mass of 3-6MJup according to evolutionary models. That object and
two other new members have redder mid-IR colors than young
photospheres at ≤M9.5, which may indicate the presence of disks.
However, since those objects may be later than M9.5 and the mid-IR
colors of young photospheres are ill-defined at those types, we cannot
determine conclusively whether color excesses from disks are present.
If ChaJ11110675-7636030 does have a disk, it would be a contender for
the least-massive known brown dwarf with a disk. Since the new brown
dwarfs that we have found extend below our completeness limit of
6-10MJup, deeper observations are needed to measure the minimum mass
of the initial mass function in Chamaeleon I.
Description:
We have compiled a catalog of the previously known members of Cha I.
We began with the census from Luhman 2008 (Cat. J/ApJ/675/1375). we
adopt ChaJ11100159-7738052 as a previously known member, which was
presented in Luhman 2007 (Cat. J/ApJS/173/104) as a possible field
M9-L1 dwarf. We also include in our census the M9 companion to CT Cha
(Schmidt et al. 2008A&A...491..311S 2008A&A...491..311S) and five new M4 members from
Frasca et al. 2015 (Cat. J/A+A/575/A4) and Sacco et al. 2017 (Cat.
J/A+A/601/A97): 2MASSJ10575375-7724495, 2MASSJ10563146-7618334,
2MASSJ11213079-7633351, 2MASSJ11130450-7534369, and
2MASSJ11090915-7553477. We list the 244 previously known members and
the 6 new members from this study in Table1.
Luhman et al. (2005ApJ...635L..93L 2005ApJ...635L..93L) obtained images of a 13.3'*16.7'
area of the southern subcluster in Cha I with the Wide Field Camera
(WFC) aperture of the Advanced Camera for Surveys (ACS) on board HST.
The observations were performed on 2004 August 21 and 2005 February 16
with the F775W and F850LP filters. To measure proper motions for
sources detected in those data, we repeated those observations in the
F850LP filter on 2009 August 20 and 2011 February 13 through program
11695.
Portions of Cha I have been imaged at several epochs with the Infrared
Array Camera (IRAC) on Spitzer. Those observations occurred during
both the cryogenic and post-cryogenic phases of the mission. The
cryogenic phase began at launch in 2003 August and continued until
2009 May, when the liquid helium was depleted. During that time, IRAC
operated with four 256*256 arrays that collected images in broadband
filters at 3.6, 4.5, 5.8, and 8.0µm, which are denoted as [3.6],
[4.5], [5.8], and [8.0]. For each array, the plate scale was
1.2''/pixel and the field of view (FOV) was 5.2'*5.2'. Point sources
within the images have a FWHM of 1.6''-1.9'' for [3.6]-[8.0].
We compiled photometry from previous surveys for low-mass members of
Cha I and publicly available catalogs, which consist of F775W and
F850LP from ACS/HST (Luhman et al. 2005ApJ...635L..93L 2005ApJ...635L..93L); F791W and
F850LP from the Wide Field Planetary Camera 2 (WFPC2) on HST (Todorov
et al. 2014, Cat. J/ApJ/788/40); I from the Inamori Magellan Areal
Camera and Spectrograph (IMACS) on the Magellan I telescope at Las
Campanas Observatory (Luhman 2007, Cat. J/ApJS/173/104); Y, J, H, and
Ks from the Infrared Side Port Imager (ISPI) at the Cerro Tololo
Inter-American Observatory (CTIO; Luhman et al. 2005ApJ...635L..93L 2005ApJ...635L..93L);
J, H, and Ks from the 2MASS Point Source Catalog (Cutri et al. 2003,
Cat. II/246); and i from the Third Release of the Deep Near-Infrared
Survey of the Southern Sky (DENIS; Epchtein et al. 1999, see Cat.
B/denis).
We obtained images of additional fields of Cha I with ISPI on the
nights of 2008 January 20-23. This instrument provided a plate scale
of 0.3pixel-1 and a FOV of 10.25'*10.25'. These observations
consisted of 16*60s exposures in each of three filters (J, H, Ks)
and in each of four adjacent fields. The data were reduced in the same
manner as the previous ISPI observations (Luhman et al.
2005ApJ...635L..93L 2005ApJ...635L..93L; Luhman 2007, Cat. J/ApJS/173/104). The typical
FWHM for point sources in these images was 0.95''.
We performed optical imaging of Cha I with the Dark Energy Camera
(DECam) at the 4m Blanco telescope at CTIO. The instrument contains 62
CCDs with dimensions of 2048*4096 pixels and plate scales of
0.27''/pixel. The FOV of the entire mosaic has a diameter of ∼2°.
In an initial set of shallow observations on 2013 May 30, we obtained
three dithered images in each i, z, and Y with individual exposures
times of 200, 30, and 30s, respectively. We collected deeper data on
2015 March 5 in which the numbers of images and exposure times were
49*150s (i), 79*100s (z), and 46*200s (Y). To extend the dynamic range
to brighter magnitudes, we also obtained 7*0.7s images for each filter
during that night. The images were reduced by the DECam pipeline. The
typical FWHM for point sources in these images was 0.8''.
Two publicly available Ks-band imaging programs of Cha I have been
performed by the High Acuity Wide-field K-band Imager (HAWK-I) on the
Unit Telescope 4 of the Very Large Telescope (VLT). This camera
contains four 2048*2048 HAWAII-2RG arrays that have a plate scale of
0.106''/pixel and an FOV of 7.5'*7.5'. On the nights of 2008 January
24, 27-29, and 31, four fields were imaged through program
60.A-9284(L). In each field, 25 dithered images were taken, each
consisting of 15 co-added 2.0s exposures. Four additional fields were
imaged on the nights of 2010 May 12 and 2010 July 5-6 through program
385.C-0384(A). For each field, 200 images were taken with exposure
times of 3s. We reduced the individual exposures from HAWK-I by
subtracting a dark frame and dividing by a flat-field image using
tasks within IRAF. The resulting images were then registered and
combined into mosaics. For most of these images, the typical FWHM for
point sources was 0.8'' except for the nights of 2010 July 5-6, when
it was 1.5''.
We performed optical spectroscopy on two targets,
2MASSJ10575375-7724495 and 2MASSJ11093277-7638376, with the Goodman
High Throughput Spectrograph at the Southern Astrophysical Research
Telescope on 2014 May 7 and 2014 June 16, respectively. The instrument
was operated with the 400 line/mm grating in second order, the GG445
filter, and the 0.84'' slit, which produced a wavelength coverage of
5400-9400Å with resolution of R=1100. Spectra of six candidates
were obtained with FLAMINGOS-2 on the Gemini South Telescope on
January 23 and February 2, 3, and 5 in 2015. For the brightest target,
2MASSJ11124771-7737547, the instrument was configured with the JH
grism and filter and the 1.08'' slit (0.70-2.04µm, R=300). The
other five FLAMINGOS-2 targets, ChaJ11110675-7636030,
ChaJ11064106-7745040, ChaJ11105004-7721535, ChaJ11105772-7714570, and
ChaJ11104183-7633064, were observed with the HK grism and filter and
the 0.72'' slit (1.10-2.65µm, R=450). We observed
2MASSJ10543141-7710130, 2MASSJ10532815-7710268, and
2MASSJ11065677-7725478 with ARCoIRIS on the 4m Blanco telescope at
CTIO on the nights of 2016 June 17 and 18 (0.8-2.47µm, R=3500).
Objects:
-----------------------------------------------------------
RA (ICRS) DE Designation(s)
-----------------------------------------------------------
11 06 48 -77 18.0 Chamaeleon I = XSS J11094-7650
-----------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 124 250 Members of Chamaeleon I
table3.dat 41 6 New members of Chamaeleon I
table4.dat 155 12 Mid-infrared photometry for members of Chamaeleon I
found since Luhman 2008 (Cat. J/ApJ/675/1375)
--------------------------------------------------------------------------------
See also:
B/denis : The DENIS database (DENIS Consortium, 2005)
II/328 : AllWISE Data Release (Cutri+ 2013)
II/311 : WISE All-Sky Data Release (Cutri+ 2012)
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
J/A+A/601/A97 : Gaia-ESO Survey: Cha I members (Sacco+, 2017)
J/A+A/575/A4 : Activity and accretion in γ Vel and ChaI (Frasca+, 2015)
J/ApJ/788/40 : Late-type targets in Taurus, Cha I, and U Sco (Todorov+, 2014)
J/ApJS/186/111 : Spitzer observations of Taurus members (Luhman+, 2010)
J/ApJ/675/1375 : IRAC/MIPS photometry in Cha I (Luhman+, 2008)
J/ApJS/173/104 : Stellar population in Chamaeleon I (Luhman, 2007)
J/AJ/124/1001 : JHKs photometry of Cha I variables (Carpenter, 2002)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 24 A24 --- Name Source name (1)
26- 41 A16 --- OName ? Other source name
43- 47 A5 --- SpT ? Adopted spectral type
49- 51 A3 --- r_SpT ? Spectral type reference (2)
53- 57 F5.1 mas/yr pmRA [-22.7/-2]? IRAC relative proper motion in Right
Ascension
59- 61 F3.1 mas/yr e_pmRA [0/7.9]? Error in pmRA
63- 66 F4.1 mas/yr pmDE [-8.1/19.5]? IRAC relative proper motion in
Declination
68- 70 F3.1 mas/yr e_pmDE [0/9.8]? Error in pmDE
72- 76 A5 --- f_pmDE ? Flag on IRAC relative proper motions
(err, nodet, out, sat, or unres) (3)
78- 81 F4.2 mag AJ [0/5.6]? Extinction in J
83- 85 A3 --- r_AJ ? Reference for AJ (4)
87- 91 F5.2 mag Jmag [7.15/19.74]? J band magnitude
93- 96 F4.2 mag e_Jmag [0/0.15]? Error in Jmag
98-102 F5.2 mag Hmag [6.67/18.39]? H band magnitude
104-107 F4.2 mag e_Hmag [0/0.17]? Error in Hmag
109-113 F5.2 mag Ksmag [5.94/17.19]? Ks band magnitude
115-118 F4.2 mag e_Ksmag [0/0.12]? Error in Ksmag
120-124 A5 --- r_Ksmag ? JHK magnitude reference (5)
--------------------------------------------------------------------------------
Note (1): Coordinate-based identifications from the 2MASS point source catalog
(Cutri et al. 2003, Cat. II/246) when available. Otherwise, identifications
are based on the coordinates measured in this work or Luhman 2008
(Cat. J/ApJ/675/1375).
Note (2): The references are defined as follows:
1 = Luhman 2008 (Cat. J/ApJ/675/1375), references therein;
2 = Frasca et al. 2015 (Cat. J/A+A/575/A4);
3 = This work;
4 = Revised classification of spectrum from Luhman et al.
(2006ApJ...649..894L 2006ApJ...649..894L);
5 = Revised classification of spectrum from Luhman 2007
(Cat. J/ApJS/173/104).
Note (3): The flags on relative proper motions are defined as follows:
nodet = Non-detection in IRAC;
unres = Unresolved from bright companion (too close to a brighter star to
be detected);
sat = Saturated;
out = Outside of overlapping multi-epoch IRAC images;
err = Motion error above our adopted thresholds.
Note (4): Extinction in J references are defined as follows:
1 = Luhman 2007 (Cat. J/ApJS/173/104);
2 = Luhman & Muench 2008 (Cat. J/ApJ/684/654);
3 = Luhman et al. 2008 (Cat. J/ApJ/675/1375);
sp = Derived from spectrum with spectral templates from Luhman et al.
(2017AJ....153...46L 2017AJ....153...46L; see 2017, Cat. J/AJ/153/46);
J-H = Derived from the 2MASS J-H color assuming photospheric near-infrared
colors (Luhman et al. 2010, Cat. J/ApJS/186/111).
Note (5): The references for the JHKs magnitudes are defined as follows:
2 = 2MASS Point Source Catalog (Cutri et al. 2003, Cat. II/246);
l = Luhman et al. (2005ApJ...635L..93L 2005ApJ...635L..93L);
i = Infrared Side Port Imager (ISPI) data from this work;
h = High Acuity Wide-field K-band Imager (HAWK-I) data from this work;
c = Carpenter et al. 2002 (Cat. J/AJ/124/1001).
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 23 A23 --- Name Source name (1)
25- 29 A5 --- SpT Spectral type
31- 41 A11 --- Spect Spectrograph
--------------------------------------------------------------------------------
Note (1): Coordinate-based identifications from the 2MASS Point Source Catalog
(Cutri et al. 2003, Cat. II/246) when available. Otherwise, identifications
are based on the coordinates measured in this work.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 23 A23 --- Name Source name
25 A1 --- f_Name [b] WISE photometric flag for
Cha J11100159-7738052 (1)
27- 31 F5.2 mag W1mag [9.78/16.57]? W1 magnitude (3.5µm) (2)
33- 36 F4.2 mag e_W1mag [0.02/0.4]? Error in W1mag
38 A1 --- f_W1mag [c] Flag on W1mag (c=blended with another star)
40- 44 F5.2 mag W2mag [9.69/16.25]? W2 magnitude (4.5µm) (2)
46- 49 F4.2 mag e_W2mag [0.02/0.18]? Error in W2mag
51 A1 --- f_W2mag [c] Flag on W2mag (c=blended with another star)
53 A1 --- l_W3mag [>] Lower limit flag on W3mag
54- 58 F5.2 mag W3mag [8.66/13.2]? W3 magnitude (12µm) (2)
60- 63 F4.2 mag e_W3mag [0.02/0.24]? Error in W3mag
65 A1 --- f_W3mag [d] Flag on W3mag (d) (3)
67 A1 --- l_W4mag [>] Lower limit flag on W4mag
68- 71 F4.2 mag W4mag [7.33/9.73]? W4 magnitude (22µm) (2)
73- 76 F4.2 mag e_W4mag [0.03/0.33]? Error in W4mag
78 A1 --- f_W4mag [a] Flag on W4mag for false or unreliable detection
based on visual inspection
80- 84 F5.2 mag [3.6] [10.23/15.94]? Spitzer/IRAC 3.6µm band
magnitude (4)
86- 89 F4.2 mag e_[3.6] [0.02/0.02]? Error in [3.6]
91- 93 A3 --- f_[3.6] [out] Outside flag on [3.6] (5)
95- 99 F5.2 mag [4.5] [10.18/15.67]? Spitzer/IRAC 4.5µm band
magnitude (4)
101-104 F4.2 mag e_[4.5] [0.02/0.02]? Error in [4.5]
106-108 A3 --- f_[4.5] [out] Outside flag on [4.5] (5)
110-114 F5.2 mag [5.8] [14.36/15.79]? Spitzer/IRAC 5.8µm band
magnitude (4)
116-119 F4.2 mag e_[5.8] [0.02/0.13]? Error in [5.8]
121-123 A3 --- f_[5.8] [out] Outside flag on [5.8] (5)
125-129 F5.2 mag [8.0] [13.62/14.74]? Spitzer/IRAC 8.0µm band
magnitude (4)
131-134 F4.2 mag e_[8.0] [0.02/0.13]? Error in [8.0]
136-138 A3 --- f_[8.0] [out] Outside flag on [8.0] (5)
140-143 F4.2 mag [24] [9]? Spitzer/MIPS 24µm band magnitude (6)
145-148 F4.2 mag e_[24] [0.11/0.11]? Error in [24]
150-152 A3 --- f_[24] [out] Outside flag on [24] (5)
154 A1 --- Exc [NY] Excess? (Yes or No)
155 A1 --- u_Exc [?] Uncertainty flag on E
--------------------------------------------------------------------------------
Note (1): Photometry for Cha J11100159-7738052 is not reported in the AllWISE
Source Catalog (Cutri et al. 2013, Cat. II/328), so we list the data from
the WISE All-Sky Source catalog (Cutri et al. 2012, Cat. II/311).
Note (2): From AllWISE Source Catalog (Cutri et al. 2013, Cat. II/328). Ellipses
indicate measurements that are absent because of nondetection.
Note (3): The AllWISE Source Catalog (Cutri et al. 2013, Cat. II/328) reports a
detection, but it appears to be offset from the detections in W1 and W2.
Note (4): IRAC=Infrared Array Camera.
Note (5): out=position outside of the camera's Field Of View (FOV).
Note (6): MIPS=Multiband Imaging Photometer for Spitzer.
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Prepared by [AAS]; Sylvain Guehenneux [CDS] 13-Oct-2017