J/AJ/153/99 Galactic outer disk: a field toward Tombaugh 1 (Carraro+, 2017)
Galactic structure in the outer disk: the field in the line of sight to
the intermediate-age open cluster Tombaugh 1.
Carraro G., Sales Silva J.V., Moni Bidin C., Vazquez R.A.
<Astron. J., 153, 99-99 (2017)>
=2017AJ....153...99C 2017AJ....153...99C (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Clusters, open ; Photometry, VRI ; Abundances ;
Effective temperatures ; Radial velocities ; Reddening ;
Stars, distances ; Equivalent widths
Keywords: Galaxy: disk - Hertzsprung-Russell and C-M diagrams -
open clusters and associations: general - stars: abundances
Abstract:
We employ optical photometry and high-resolution spectroscopy to study
a field toward the open cluster Tombaugh 1, where we identify a
complex population mixture that we describe in terms of young and old
Galactic thin disks. Of particular interest is the spatial
distribution of the young population, which consists of dwarfs with
spectral types as early as B6 and is distributed in a blue plume
feature in the color-magnitude diagram. For the first time, we confirm
spectroscopically that most of these stars are early-type stars and
not blue stragglers or halo/thick-disk subdwarfs. Moreover, they are
not evenly distributed along the line of sight but crowd at heliocentric
distances between 6.6 and 8.2 kpc. We compare these results with
present-day understanding of the spiral structure of the Galaxy and
suggest that they trace the outer arm. This range of distances challenges
current Galactic models adopting a disk cutoff at 14 kpc from the
Galactic center. The young dwarfs overlap in space with an older
component, which is identified as an old Galactic thin disk. Both young
and old populations are confined in space since the disk is warped at
the latitude and longitude of Tombaugh 1. The main effects of the warp
are that the line of sight intersects the disk and entirely crosses it
at the outer arm distance and that there are no traces of the closer
Perseus arm, which would then be either unimportant in this sector or
located much closer to the formal Galactic plane. Finally, we analyze
a group of giant stars, which turn out to be located at very different
distances and to possess very different chemical properties, with no
obvious relation to the other populations.
Description:
The region of interest has been observed with the Y4KCAM camera
attached to the 1.0 m telescope operated by the SMARTS consortium
(http://www.astro.yale.edu/smarts/) and located at the Cerro Tololo
Inter-American Observatory (CTIO). This camera is equipped with an STA
4064x4064 CCD with 15 µm pixels, yielding a scale of 0.289"/pixel
and a field of view (FOV) of 20'x20' at the Cassegrain focus of the
CTIO 1.0 m telescope.
The observational data were acquired on the night of 2008 January 30.
We observed Landolt's SA 98 UBV(RI)KC standard star area
(Landolt 1992AJ....104..372L 1992AJ....104..372L) to tie our UBVRI instrumental system to
the standard system. The average seeing was 1.0".
During the nights of 2010 January 5, 6, 9, and 10, we observed 40 stars
of the field toward the open cluster Tombaugh 1 (10 stars from boxes A
and B, 11 stars from box C, and 9 stars from box D) on Cerro Manqui at
the Las Campanas Observatory using the Inamori-Magellan Areal
Camera & Spectrograph (IMACS; Dressler et al. 2006SPIE.6269E..0FD),
attached to the 6.5 m Magellan Telescope.
Objects:
-----------------------------------------------------
RA (ICRS) DE Designation(s)
-----------------------------------------------------
07 00 29 -20 34.0 Tombaugh 1 = C 0658-204
-----------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 46 31 Fundamental Information for
the Spectroscopically Observed Stars
table3.dat 109 8 Atmospheric Parameters from Spectroscopy
of Stars of Box B
table4.dat 110 8 Abundance Ratios ([X/Fe]) for the Elements,
from Na to Cr, for the Stars from Box B
table6.dat 62 94 Observed Fe I and Fe II Lines
table7.dat 62 77 Other Lines Studied
table9.dat 109 11 Atmospheric Parameters from Spectroscopy
of Stars of Box C
table10.dat 109 9 Atmospheric Parameters from Spectroscopy
of Stars of Box D
--------------------------------------------------------------------------------
See also:
J/A+A/275/101 : Chemical evolution of the galactic disk I. (Edvardsson+ 1993)
J/A+A/350/955 : Atmospheric parameters in metal-poor stars. II
(Gratton+, 1999)
J/MNRAS/340/304 : [X/Fe] of Galactic disc F and G dwarfs (Reddy+, 2003)
J/A+A/421/991 : CT1 photometry in Tombaugh 1 (Piatti+, 2004)
J/AJ/144/95 : Abundance in stars of the outer galactic disk. IV.
(Yong+, 2012)
J/AJ/151/6 : Spectroscopic and photometric properties of Tombaugh 1
(Sales+, 2016)
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1 A1 --- Box [BCD] Box designation
3- 7 I5 --- ID [6507/36132] Star identification number
9- 19 F11.7 deg RAdeg Right Ascension in decimal degrees (J2000)
21- 31 F11.7 deg DEdeg Declination in decimal degrees (J2000)
33- 37 F5.2 mag Vmag [15.57/19.38] V band magnitude
39- 43 F5.3 mag V-I [0.458/1.512] V-I color index
45- 46 I2 --- S/N [10/75] Spectral signal-to-noise ratio at 6000Å
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table3.dat table9.dat table10.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 I5 --- ID [6507/36132] Star identification number
6 A1 --- n_ID [abc] Note on ID (1)
8- 12 I5 K Teff [4600/14500]? Effective temperature
14- 17 I4 K e_Teff [20/4200]? Uncertainty in Teff
19- 21 F3.1 [cm/s2] logg [2/5.5]? Surface gravity (not in table 10)
(dex)
23- 25 F3.1 [cm/s2] e_logg [0/3.2]? Uncertainty in logg
(not in table 10)
27- 29 F3.1 km/s ksi [1.5/3]? Microturbulent velocity ξ
(only in table 3)
31- 33 F3.1 km/s e_ksi [0.3/1]? Uncertainty in ksi (only in table 3)
35- 37 I3 km/s vsini [0/310]? Rotational velocity
(only in table 9)
38 A1 --- n_vsini [c] Note on visini (only in table 9) (1)
40- 44 F5.2 [-] [FeI/H] [-0.68/0.03]? Abundance ratio [FeI/H]
(only in table 3)
46- 49 F4.2 [-] e_[FeI/H] [0.13/0.34]? Uncertainty in [FeI/H]
(only in table 3)
51- 52 I2 --- o_[FeI/H] [16/43]? Number of FeI lines employed
(only in table 3)
54- 58 F5.2 [-] [FeII/H] [-0.7/0.05]? Abundance ratio [FeII/H]
(only in table 3)
60- 63 F4.2 [-] e_[FeII/H] [0.07/0.26]? Uncertainty in [FeII/H]
(only in table 3)
65 I1 --- o_[FeII/H] [1/8]? Number of FeII lines employed
(only in table 3)
67- 71 F5.1 km/s RVmean [0.9/139] Mean radial velocity
73- 76 F4.1 km/s e_RVmean [0.3/45] Uncertainty in RVmean
78- 81 F4.2 --- E(V-I) [0.3/0.82]? Reddening
83- 86 F4.2 --- e_E(V-I) [0.02/0.28]? Uncertainty in E(V-I)
88- 92 F5.2 mag (m-MV)0 [10.46/16.81]? Reddening-corrected distance
modulus (m-MV)0
94- 97 F4.2 mag e_(m-MV)0 [0.05/1.74]? Uncertainty in (V-Mnu)0
99-103 I5 pc Dist [1200/23000]? Distance
105-109 I5 pc e_Dist [100/11600]? Uncertainty in Dist
--------------------------------------------------------------------------------
Note (1): Note as follows:
a = Large uncertainty in the atmospheric parameters and metallicity of this
star due to low S/N;
b = Problem in obtaining the microturbulent velocity (ξ) due to the low
number of absorption lines with a small equivalent width, causing
considerable uncertainty in the metallicity;
c = No Hβ line.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 I5 --- ID [11029/32782] Star identification number
7- 11 F5.2 [-] [Na/Fe] [0.19/0.42]? Abundance ratio [Na/Fe] (1)
13- 16 F4.2 [-] e_[Na/Fe] [0.01]? Uncertainty in [Na/Fe]
18 I1 --- o_[Na/Fe] [1/2]? Number of Na lines employed
20- 24 F5.2 [-] [Mg/Fe] [-0.21/0.67]? Abundance ratio [Mg/Fe]
26- 29 F4.2 [-] e_[Mg/Fe] [0.06/0.13]? Uncertainty in [Mg/Fe]
31 I1 --- o_[Mg/Fe] [1/2]? Number of Mg lines employed
33- 37 F5.2 [-] [Al/Fe] [0.1/0.59]? Abundance ratio [Al/Fe]
39- 42 F4.2 [-] e_[Al/Fe] [0.01/0.11]? Uncertainty in [Al/Fe]
44 I1 --- o_[Al/Fe] [1/4]? Number of Al lines employed
46- 50 F5.2 [-] [Si/Fe] [0.07/0.54]? Abundance ratio [Si/Fe]
52- 55 F4.2 [-] e_[Si/Fe] [0.05/0.17]? Uncertainty in [Si/Fe]
57 I1 --- o_[Si/Fe] [1/3]? Number of Si lines employed
59- 63 F5.2 [-] [Ca/Fe] [-0.3/0.47]? Abundance ratio [Ca/Fe]
65- 68 F4.2 [-] e_[Ca/Fe] [0.03/0.17]? Uncertainty in [Ca/Fe]
70 I1 --- o_[Ca/Fe] [2/4]? Number of Ca lines employed
72- 76 F5.2 [-] [Ti/Fe] [0.21/0.54] Abundance ratio [Ti/Fe]
78- 81 F4.2 [-] e_[Ti/Fe] [0.03/0.15] Uncertainty in [Ti/Fe]
83 I1 --- o_[Ti/Fe] [2/6] Number of Ti lines employed
85- 89 F5.2 [-] [Cr/Fe] [-0.21/0.35] Abundance ratio [Cr/Fe]
91- 94 F4.2 [-] e_[Cr/Fe] [0.02/0.13]? Uncertainty in [Cr/Fe]
96 I1 --- o_[Cr/Fe] [1/3] Number of Cr lines employed
98-102 F5.2 [-] [Ni/Fe] [-0.22/0.24] Abundance ratio [Ni/Fe]
104-107 F4.2 [-] e_[Ni/Fe] [0.07/0.16]? Uncertainty in [Ni/Fe]
109-110 I2 --- o_[Ni/Fe] [1/11] Number of Ni lines employed
--------------------------------------------------------------------------------
Note (1): [Na/Fe] accounts for the nonlocal thermodynamic equilibrium (NLTE)
effects calculated as in Gratton et al. (1999, J/A+A/350/955) - see
the text.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table6.dat table7.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- El Element
7- 13 F7.2 0.1nm lambda [4730.04/8773.91] Wavelength λ (Å)
15- 18 F4.2 eV chi [0.02/6.18] Excitation potential χ
20- 25 F6.3 [-] loggf [-5.95/0.42] Oscillator strength (1)
27- 30 A4 --- Ref Reference of the atomic parameters
(only in table 7) (2)
32- 34 I3 0.1pm EW-11029 [20/160]? Equivalent width for star 11029 (mÅ)
36- 38 I3 0.1pm EW-13540 [23/156]? Equivalent width for star 13540 (mÅ)
40- 42 I3 0.1pm EW-13964 [40/154]? Equivalent width for star 13964 (mÅ)
44- 46 I3 0.1pm EW-26606 [36/147]? Equivalent width for star 26606 (mÅ)
48- 50 I3 0.1pm EW-27955 [17/149]? Equivalent width for star 27955 (mÅ)
52- 54 I3 0.1pm EW-28064 [10/153]? Equivalent width for star 28064 (mÅ)
56- 58 I3 0.1pm EW-31364 [22/151]? Equivalent width for star 31364 (mÅ)
60- 62 I3 0.1pm EW-32782 [40/155]? Equivalent width for star 32782 (mÅ)
--------------------------------------------------------------------------------
Note (1): The values of the oscillator strength adopted for the Fe I and Fe II
lines were taken from Lambert et al. (1996ApJS..103..183L 1996ApJS..103..183L) and
Castro et al. (1997AJ....114..376C 1997AJ....114..376C).
Note (2): Reference as follows:
B86 = Blackwell et al. (1986MNRAS.220..289B 1986MNRAS.220..289B);
DS91 = Drake & Smith (1991MNRAS.250...89D 1991MNRAS.250...89D);
E93 = Edvardsson et al. (1993, J/A+A/275/101);
GS = Gratton & Sneden (1988A&A...204..193G 1988A&A...204..193G);
MFK = Martin et al. (2002nla..work...80R);
MR94 = McWilliam & Rich (1994ApJS...91..749M 1994ApJS...91..749M);
PS = Preston & Sneden (2001AJ....122.1545P 2001AJ....122.1545P);
R03 = Reddy et al. (2003, J/MNRAS/340/304);
R99 = Reddy et al. (1999ApJ...524..831R 1999ApJ...524..831R);
S86 = Not explained in this paper;
WSM = Wiese et al. (1969atp..book.....W 1969atp..book.....W).
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History:
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(End) Tiphaine Pouvreau [CDS] 18-Apr-2018