J/ApJ/756/79 Optical photometry in 3 Local Group dwarf galaxies (Sand+, 2012)
Tidal signatures in the faintest Milky Way satellites: the detailed properties
of Leo V, Pisces II, and Canes venatici II.
Sand D.J., Strader J., Willman B., Zaritsky D., McLeod B., Caldwell N.,
Seth A., Olszewski E.
<Astrophys. J., 756, 79 (2012)>
=2012ApJ...756...79S 2012ApJ...756...79S
ADC_Keywords: Galaxies, nearby ; Photometry, VRI
Keywords: galaxies: dwarf; Local Group
Abstract:
We present deep wide-field photometry of three recently discovered
faint Milky Way (MW) satellites: Leo V, Pisces II, and Canes Venatici II.
Our main goals are to study the structure and star formation history
of these dwarfs; we also search for signs of tidal disturbance. The
three satellites have similar half-light radii (∼60-90pc) but a wide
range of ellipticities. Both Leo V and CVn II show hints of
stream-like overdensities at large radii. An analysis of the satellite
color-magnitude diagrams shows that all three objects are old (>10Gyr)
and metal-poor ([Fe/H]~-2), though neither the models nor the data
have sufficient precision to assess when the satellites formed with
respect to cosmic reionization. The lack of an observed younger
stellar population (≲10Gyr) possibly sets them apart from the other
satellites at Galactocentric distances ≳150kpc. We present a new
compilation of structural data for all MW satellite galaxies and use
it to compare the properties of classical dwarfs to the ultra-faints.
The ellipticity distribution of the two groups is consistent at the
∼2σ level. However, the faintest satellites tend to be more
aligned toward the Galactic Center, and those satellites with the
highest ellipticity (≳0.4) have orientations (ΔθGC) in
the range 20°≲ΔθGC≲40°. This latter
observation is in rough agreement with predictions from simulations of
dwarf galaxies that have lost a significant fraction of their dark
matter halos and are being tidally stripped.
Description:
We observed Leo V on 2010 April 13 (UT) and Pisces II on 2010 October
3 (UT) with Megacam on the f/5 focus at the Magellan Clay telescope in
the g and r bands.
The Subaru/Suprimecam data of CVn II come from the SMOKA science
archive. While other data on CVn II are available, we retrieved the
deep V and I imaging observed by Okamoto and collaborators (see
Okamoto et al. 2012ApJ...744...96O 2012ApJ...744...96O) on 2008 Apr 3 and 5.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 62 37522 Leo V gr-photometry with Megacam
table3.dat 62 23538 Pisces II gr-photometry with Megacam
table4.dat 64 42491 CVn II VI-photometry with Subaru
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See also:
J/AJ/144/4 : Dwarf galaxies in the Local Group (McConnachie+, 2012)
J/AJ/142/88 : Segue 3 photometric and kinematic data (Fadely+, 2011)
J/ApJ/718/530 : Leo IV g- and r-band photometry (Sand+, 2010)
J/ApJ/710/1664 : BV photometry in Leo IV and Leo V dSphs (de Jong+, 2010)
J/ApJ/694/L144 : Spectroscopic study of Leo V dSph (Walker+, 2009)
J/MNRAS/360/185 : VI photometry of the Leo II galaxy (Bellazzini+, 2005)
J/MNRAS/354/708 : Leo I VI photometry (Bellazzini+, 2004)
J/AJ/126/2840 : BVI CCD photometry of Sextans dSph galaxy (Lee+, 2003)
http://www.sdss.org/ : SDSS home page
Byte-by-byte Description of file: table[23].dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 I5 --- Seq Running sequence number (starting at "0")
7- 15 F9.5 deg RAdeg Right Ascension in decimal degrees (J2000)
17- 25 F9.6 deg DEdeg Declination in decimal degrees (J2000)
27- 31 F5.2 mag gmag [14.5/28] CFHT/Megacam g band magnitude (1)
33- 36 F4.2 mag e_gmag [0.01/0.6] Uncertainty in gmag
38- 41 F4.2 mag Ag [0.08/0.3] Schlegel et al.
1998ApJ...500..525S 1998ApJ...500..525S g-band extinction
43- 47 F5.2 mag rmag [15/27.6] CFHT/Megacam r band magnitude (1)
49- 52 F4.2 mag e_rmag [0.01/0.6] Uncertainty in rmag
54- 57 F4.2 mag Ar [0.06/0.3] Schlegel et al.
1998ApJ...500..525S 1998ApJ...500..525S r-band extinction
59- 62 A4 --- Inst Photometry source (2)
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Note (1): Uncorrected for extinction.
Note (2): Photometry source as follows:
SDSS = SDSS catalog;
Mag = Our Magellan/Megacam photometry
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Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 I5 --- Seq [0/42490] Running sequence number
7- 15 F9.5 deg RAdeg Right Ascension in decimal degrees (J2000)
17- 25 F9.6 deg DEdeg Declination in decimal degrees (J2000)
27- 31 F5.2 mag Vmag [14.7/27.4] Subaru V band magnitude (1)
33- 36 F4.2 mag e_Vmag [0.01/0.6] Uncertainty in Vmag
38- 41 F4.2 mag Av [0.03/0.04] Schlegel et al.
1998ApJ...500..525S 1998ApJ...500..525S V-band extinction
43- 47 F5.2 mag Imag [15/27] Subaru I band magnitude (1)
49- 52 F4.2 mag e_Imag [0.01/0.6] Uncertainty in Imag
54- 57 F4.2 mag Ai [0.01/0.02] Schlegel et al.
1998ApJ...500..525S 1998ApJ...500..525S I-band extinction
59- 64 A6 --- Inst Photometry source (2)
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Note (1): Uncorrected for extinction. We used the filter transformations of
Jordi et al. (2006A&A...460..339J 2006A&A...460..339J) to convert from SDSS catalog
magnitudes to V and I bands.
Note (2): Photometry source as follows:
SDSS = SDSS catalog;
Subaru = Our Subaru/Suprimecam photometry.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 25-Mar-2014