J/MNRAS/485/2010 Kinematics of the Tucana Dwarf Galaxy (Gregory+, 2019)
Kinematics of the Tucana Dwarf Galaxy: an unusually dense dwarf in the Local
Group.
Gregory A.L., Collins M.L.M., Read J.I., Irwin M.J., Ibata R.A.,
Martin N.F., McConnachie A.W., Weisz D.R.
<Mon. Not. R. Astron. Soc., 485, 2010-2025 (2019)>
=2019MNRAS.485.2010G 2019MNRAS.485.2010G (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, optical ; Galaxies, photometry ; Galaxies, spectra
Keywords: galaxies: dwarf - galaxies: evolution - galaxies: haloes -
galaxies: kinematics and dynamics - Local Group
Abstract:
We present new FLAMES+GIRAFFE spectroscopy of 36 member stars in the
isolated Local Group dwarf spheroidal galaxy Tucana. We measure a
systemic velocity for the system of vTuc=216.7+2.9-2.8km/s, and
a velocity dispersion of σv,Tuc=14.4+2.8-2.3km/s. We also
detect a rotation gradient of dvr/dΧ=7.6+4.2-4.3km/s/kpc,
which reduces the systemic velocity to vTuc=215.2+2.8-2.7km/s
and the velocity dispersion to σv,Tuc=13.3+2.7-2.3km/s. We
perform Jeans modelling of the density profile of Tucana, using the
line-of-sight velocities of the member stars. We find that it favours
a high central density consistent with 'pristine' subhaloes in
Λ cold dark matter, and a massive dark matter halo
(∼1010M☉) consistent with expectations from abundance
matching. Tucana appears to be significantly more centrally dense than
other isolated Local Group dwarfs, making it an ideal laboratory for
testing dark matter models.
Description:
Photometric data for Tucana was obtained using the Magellan/Megacam
instrument on the Clay telescope at Las Campanas observatory on 2012
November 14 as part of the Solo (Solitary Local Dwarfs) observing
campaign (Higgs et al. 2016MNRAS.458.1678H 2016MNRAS.458.1678H). Magellan/Megacam is a 9x4
array of pixel CCDs with a pixel scale 0.08arcsec/pixel. Two pointings
were targeted, with three exposures were stacked in both the g and i
bands for each field. Each g-band exposure was 150s for a total
integration time of 450s. In the i band, the exposures were 300s each
for a total integration time of 900s. Seeing ranged from 0.68 to
0.90arcsec in the g band and 0.55 to 0.72 in the i band. The
photometry was reduced using the Cambridge Astronomical Survey Unit
(CASU), following the process described in Richardson et al.
(2011ApJ...732...76R 2011ApJ...732...76R) and Higgs et al. (2016MNRAS.458.1678H 2016MNRAS.458.1678H).
To obtain accurate spectroscopy of the faint stellar population of
Tucana, the 8.2m VLT in Paranal, Chile was used. Observations were
taken using the FLAMES+GIRAFFE spectrograph over six nights through
2015 June, August, and September. GIRAFFE is a fibre-fed spectrograph
for the visible range 3700-9000Å.
The FLAMES+GIRAFFE spectrograph is a higher resolution instrument than
FORS2 (which was used in Fraternali et al. (2009A&A...499..121F 2009A&A...499..121F)
(F09)), with a resolving power of R=6500 as opposed to R=3200. F09
observe 23 stars to an S/N suitable for determining velocities, with
20 of these identified as members. We observe a much larger number of
stars out to a wider radius than F09, generating a larger catalogue of
Tucana members and reducing the uncertainties in the results.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 68 131 Details of all successfully reduced targets
observed with FLAMES+GIRAFFE
table3.dat 59 36 Details of the 36 identified members of Tucana
observed with FLAMES+GIRAFFE
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Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 I6 --- ID Object identifier
8- 12 F5.1 km/s HV Line-of-sight heliocentric velocity
14- 17 F4.1 km/s e_HV Error on HV
19- 26 F8.4 deg RAdeg Right ascension (J2000)
28- 35 F8.4 deg DEdeg Declination (J2000)
37- 41 F5.2 mag gmag g-band magnitude from Magellan/MegaCam imaging
43- 47 F5.2 mag imag i-band magnitude from Magellan/MegaCam imaging
49- 52 F4.1 pix-1 SNR Signal to noise ratio
54 A1 --- Member [Y/N] Determination of Tucana membership
56- 57 I2 --- OName ? ID of counterpart in Fraternali et al.
(2009A&A...499..121F 2009A&A...499..121F) (F09) data set,
[FTI2009] NN in Simbad
59- 63 F5.1 km/s HVF09 ? Velocity of F09 counterpart
(Fraternali et al. 2009A&A...499..121F 2009A&A...499..121F)
65- 68 F4.1 km/s e_HVF09 ? Error on HVF09
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Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 I6 --- ID Object identifier
8- 12 F5.1 km/s HV Line-of-sight heliocentric velocity
14- 17 F4.1 km/s e_HV Error on HV
19- 26 F8.4 deg RAdeg Right ascension (J2000)
28- 35 F8.4 deg DEdeg Declination (J2000)
37- 42 F6.2 arcsec Sep On-sky separation of the object from the
central coordinates of Tucana
(22 41 49.6, -64 25 10)
44- 48 F5.2 mag gmag g-band magnitude from Magellan/MegaCam imaging
50- 54 F5.2 mag imag i-band magnitude from Magellan/MegaCam imaging
56- 59 F4.1 pix-1 SNR Signal to noise ratio
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 16-Sep-2022