J/ApJ/885/53 Spectroscopy & HST photometry of galaxy Leo V (Mutlu-Pakdil+, 2019)
Signatures of Tidal Disruption in Ultra-faint Dwarf Galaxies: a Combined HST,
Gaia, and MMT/Hectochelle study of Leo V.
Mutlu-Pakdil B., Sand D.J., Walker M.G., Caldwell N., Carlin J.L.,
Collins M.L., Crnojevic D., Mateo M., Olszewski E.W., Seth A.C., Strader J.,
Willman B., Zaritsky D.
<Astrophys. J., 885, 53 (2019)>
=2019ApJ...885...53M 2019ApJ...885...53M
ADC_Keywords: Galaxies; Photometry, HST; Spectra, optical; Extinction;
Effective temperatures; Abundances, [Fe/H]
Keywords: Dwarf galaxies ; Stellar populations ; Tidal disruption ;
Galactic and extragalactic astronomy ; HST photometry ; Spectroscopy
Abstract:
The ultra-faint dwarf galaxy Leo V has shown both photometric
overdensities and kinematic members at large radii, along with a
tentative kinematic gradient, suggesting that it may have undergone a
close encounter with the Milky Way. We investigate these signs of
disruption through a combination of (I) high precision photometry
obtained with the Hubble Space Telescope (HST), (II) two epochs of
stellar spectra obtained with the Hectochelle Spectrograph on the MMT,
and (III) measurements from the Gaia mission. Using the HST data, we
examine one of the reported stream-like overdensities at large radii,
and conclude that it is not a true stellar stream, but instead a clump
of foreground stars and background galaxies. Our spectroscopic
analysis shows that one known member star is likely a binary, and
challenges the membership status of three others, including two
distant candidates that had formerly provided evidence for overall
stellar mass loss. We also find evidence that the proposed kinematic
gradient across Leo V might be due to small number statistics. We
update the systemic proper motion of Leo V, finding
(µα/cosδ,µδ)=
(0.009±0.560,-0.777±0 .314)mas/yr, which is consistent with
its reported orbit that did not put Leo V at risk of being disturbed
by the Milky Way. These findings remove most of the observational
clues that suggested Leo V was disrupting; however, we also find new
plausible member stars, two of which are located >5 half-light radii
from the main body. These stars require further investigation.
Therefore, the nature of Leo V still remains an open question.
Description:
We have obtained deep optical observations of the candidate debris
stream of Leo V, which was identified in ground-based
(Magellan/Megacam) data, using the F606W and F814W filters on the
Hubble Space Telescope / Advanced Camera for Surveys (HST/ACS;
PI:D.Sand).
Spectroscopic data were obtained with the Hectochelle multiobject
fiber spectrograph at the Multi Mirror Telescope (MMT). Hectochelle
has a 1deg diameter field of view and can achieve ∼1km/s velocity
precision for high S/N data; the effective resolution for our setup
was R∼32000. Both data sets were taken with the "RV31" filter in
place, giving a spectral range of 5150-5300Å, which contains the
prominent Mg-b triplet.
Objects:
---------------------------------------------
RA (J2000) DE Designation(s)
---------------------------------------------
11 31 09.60 +02 13 12.0 Leo V = NAME Leo V
---------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 62 2466 Photometry of field 1-ACS: central pointing of
Leo V
table3.dat 62 1231 Photometry of field 2-ACS: candidate debris stream
of Leo V
table4.dat 62 538 Photometry of field 1-WFC3: parallel observations
of Leo V with WFC3
table5.dat 62 416 Photometry of field 2-WFC3: parallel observations
of candidate debris stream of Leo V with WFC3
table6.dat 74 140 Hectochelle stellar spectroscopy of Leo V
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See also:
J/AJ/130/1693 : HST-ACS observations of 5 globular clusters (Brown+, 2005)
J/AJ/129/2714 : JHK photometry of M92 variable stars (Del Principe+, 2005)
J/AJ/136/2050 : SEGUE stellar parameter pipeline. II. (Lee+, 2008)
J/ApJ/675/201 : Radial velocities of stars near Leo I (Mateo+, 2008)
J/MNRAS/397/1748 : Spectroscopic study of Segue 2 (Belokurov+, 2009)
J/ApJ/704/898 : Photometry of the Hercules dwarf galaxy (Sand+, 2009)
J/ApJ/694/L144 : Spectroscopic study of Leo V dSph (Walker+, 2009)
J/ApJ/710/1664 : BV photometry in Leo IV and Leo V dSphs (de Jong+, 2010)
J/ApJ/718/530 : Leo IV g- and r-band photometry (Sand+, 2010)
J/AJ/142/22 : Heavy-element dispersion in M92 (Roederer+, 2011)
J/ApJ/756/79 : Optical photometry 3 Local Group dwarf galaxies (Sand+, 2012)
J/ApJ/770/16 : Spectroscopic members of Segue 2 galaxy (Kirby+, 2013)
J/MNRAS/448/2717 : Bayesian analysis of resolved stellar spectra (Walker+,2015)
J/AJ/154/155 : Abundance variations in outer halo GC NGC6229 (Johnson+, 2017)
J/ApJ/838/83 : RVel, abundances & membership in TriII (Kirby+, 2017)
J/ApJ/838/11 : Member stars in the MW satellite Tucana III (Simon+, 2017)
J/A+A/616/A12 : Gaia DR2 sources in GC and dSph (Gaia Collaboration+, 2018)
J/ApJ/866/22 : Spectroscopic analysis of Tuc III stream (Li+, 2018)
J/ApJ/863/25 : Deep Magellan/Megacam obs. 4 MWsatellites (Mutlu-Pakdil+,2018)
J/ApJ/863/89 : Gaia DR2 PMs of stars ultra-faint MW satellites (Simon, 2018)
J/ApJ/883/11 : Magellan/IMACS spectra of Crater II & Hercules (Fu+, 2019)
J/ApJ/870/83 : Abundances in ultra-faint dwarf gal. GruI & TriII (Ji+, 2019)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- Seq [0/2465] Internal star identifier
6- 14 F9.5 deg RAdeg [172.75/172.82] Right Ascension (J2000)
16- 24 F9.7 deg DEdeg [2.18/2.26] Declination (J2000)
26- 31 F6.3 mag F606Wmag [19.09/28.5] HST/ACS F606W band magnitude
33- 37 F5.3 mag e_F606Wmag [0.001/0.3] DOLPHOT uncertainty in F606Wmag
39- 43 F5.3 mag AF606W [0.06/0.07] Galactic extinction in F606W
45- 50 F6.3 mag F814Wmag [17.61/27.72] HST/ACS F814W band magnitude
52- 56 F5.3 mag e_F814Wmag [0.001/0.3] DOLPHOT uncertainty in F814Wmag
58- 62 F5.3 mag AF814W [0.04/0.05] Galactic extinction in F814W
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- Seq [0/1230] Internal star identifier
6- 14 F9.5 deg RAdeg [172.84/172.91] Right Ascension (J2000)
16- 24 F9.7 deg DEdeg [2.27/2.34] Declination (J2000)
26- 31 F6.3 mag F606Wmag [20.15/28.53] HST/ACS F606W band magnitude
33- 37 F5.3 mag e_F606Wmag [0.001/0.22] DOLPHOT uncertainty in F606Wmag
39- 43 F5.3 mag AF606W [0.06/0.071] Galactic extinction in F606W
45- 50 F6.3 mag F814Wmag [18.6/27.65] HST/ACS F814W band magnitude
52- 56 F5.3 mag e_F814Wmag [0.001/0.3] DOLPHOT uncertainty in F814Wmag
58- 62 F5.3 mag AF814W [0.03/0.05] Galactic extinction in F814W
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- Seq [0/537] Internal star identifier
6- 14 F9.5 deg RAdeg [172.83/172.90] Right Ascension (J2000)
16- 24 F9.7 deg DEdeg [2.12/2.19] Declination (J2000)
26- 31 F6.3 mag F606Wmag [21.01/28.4] HST/WFC3 F606W band magnitude
33- 37 F5.3 mag e_F606Wmag [0.002/0.3] DOLPHOT uncertainty in F606Wmag
39- 43 F5.3 mag AF606W [0.06/0.07] Galactic extinction in F606W
45- 50 F6.3 mag F814Wmag [20.49/27.28] HST/WFC3 F814W band magnitude
52- 56 F5.3 mag e_F814Wmag [0.003/0.3] DOLPHOT uncertainty in F814Wmag
58- 62 F5.3 mag AF814W [0.04/0.05] Galactic extinction in F814W
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Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- Seq [0/415] Internal star identifier
6- 14 F9.5 deg RAdeg [172.90/172.97] Right Ascension (J2000)
16- 24 F9.7 deg DEdeg [2.20/2.26] Declination (J2000)
26- 31 F6.3 mag F606Wmag [21.27/28.44] HST/WFC3 F606W band magnitude
33- 37 F5.3 mag e_F606Wmag [0.002/0.3] DOLPHOT uncertainty in F606Wmag
39- 43 F5.3 mag AF606W [0.072/0.073] Galactic extinction in F606W
45- 50 F6.3 mag F814Wmag [19.44/27.36] HST/WFC3 F814W band magnitude
52- 56 F5.3 mag e_F814Wmag [0.002/0.3] DOLPHOT uncertainty in F814Wmag
58- 62 F5.3 mag AF814W [0.044/0.045] Galactic extinction in F814W
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Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Star Star identifier
10- 18 F9.5 deg RAdeg [172.31/173.27] Right Ascension (J2000)
20- 26 F7.5 deg DEdeg [1.77/2.66] Declination (J2000)
28- 33 F6.1 d HJD [4614/49128] Heliocentric Julian Date;
HJD-2450000.0
35- 40 F6.1 km/s Vel [-120/345] Line-of-Sight velocity; solar rest
frame
42- 44 F3.1 km/s e_Vel [0.3/3.6] Uncertainty in Vel
46- 49 I4 K Teff [4039/5970] Effective temperature
51- 53 I3 K e_Teff [33/951] Uncertainty in Teff
55- 58 F4.2 [cm/s2] logg [0.66/4.81] log surface gravity
60- 63 F4.2 [cm/s2] e_logg [0.1/1.3] Uncertainty in logg
65- 69 F5.2 [-] [Fe/H] [-2.9/0.62] Metallicity
71- 74 F4.2 [-] e_[Fe/H] [0.05/0.98] Uncertainty in [Fe/H]
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History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 02-Jun-2021