J/ApJ/916/L19 Satellites around MW analogs from SAGA II (Karunakaran+, 2021)
Satellites around Milky Way analogs: tension in the number and fraction of
quiescent satellites seen in observations versus simulations.
Karunakaran A., Spekkens K., Oman K.A., Simpson C.M., Fattahi A.,
Sand D.J., Bennet P., Crnojevic D., Frenk C.S., Gomez F.A., Grand R.J.J.,
Jones M.G., Marinacci F., Mutlu-Pakdil B., Navarro J.F., Zaritsky D.
<Astrophys. J., 916, L19 (2021)>
=2021ApJ...916L..19K 2021ApJ...916L..19K (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, dwarf; Photometry, ultraviolet; Star Forming Region
Keywords: Dwarf galaxies; Galaxy evolution; Galaxy quenching; Quenched galaxies
Star formation
Abstract:
We compare the star-forming properties of satellites around Milky Way
(MW) analogs from the Stage II release of the Satellites Around
Galactic Analogs Survey (SAGA-II) to those from the APOSTLE and Auriga
cosmological zoom-in simulation suites. We use archival GALEX UV
imaging as a star formation indicator for the SAGA-II sample and
derive star formation rates (SFRs) to compare with those from APOSTLE
and Auriga. We compare our detection rates from the NUV and FUV bands
to the SAGA-II Hα detections and find that they are broadly
consistent with over 85% of observed satellites detected in all three
tracers. We apply the same spatial selection criteria used around
SAGA-II hosts to select satellites around the MW-like hosts in APOSTLE
and Auriga. We find very good overall agreement in the derived SFRs
for the star-forming satellites as well as the number of star-forming
satellites per host in observed and simulated samples. However, the
number and fraction of quenched satellites in the SAGA-II sample are
significantly lower than those in APOSTLE and Auriga below a stellar
mass of M*∼108M☉, even when the SAGA-II incompleteness and
interloper corrections are included. This discrepancy is robust with
respect to the resolution of the simulations and persists when
alternative star formation tracers are employed. We posit that this
disagreement is not readily explained by vagaries in the observed or
simulated samples considered here, suggesting a genuine discrepancy
that may inform the physics of satellite populations around MW
analogs.
Description:
We adopt the "complete systems" in the SAGA-II release
(Mao+ 2021, J/ApJ/907/85) as our observed sample, which consists of
127 confirmed satellites across 36 surveyed hosts with
Mhalo~(0.7-2)x1012M☉.
We use the SAGA-II optical properties, stellar masses, and distances
derived for all observed hosts and satellites, which are reproduced in
Table 1.
We also make use of data from the Galaxy Evolution Explorer (GALEX)
to search for UV emission in SAGA-II satellites to provide a
homogeneous, global star formation activity indicator for each system.
In total, 119/127 SAGA-ii satellites have archival NUV and/or FUV
coverage, and we select the deepest available imaging for the search
(26/58 tiles have depths greater than GALEX AIS data, i.e. integration
times ≫300s; Table 1).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 131 127 UV properties of observed satellites
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See also:
II/335 : Revised catalog of GALEX UV sources (GUVcat_AIS GR6+7) (Bianchi+ 2017)
J/ApJS/164/38 : UV & FIR data of nearby galaxies (Iglesias-Paramo+, 2006)
J/ApJS/173/293 : UV-Optical galaxy color-magnitude diagram I. (Wyder+, 2007)
J/ApJS/192/6 : A GALEX UV imaging survey of nearby galaxies (Lee+, 2011)
J/AJ/144/4 : Dwarf galaxies in the Local Group (McConnachie+, 2012)
J/AJ/156/18 : APOGEE DR14: companions of evolved stars (Price-Whelan+, 2018)
J/ApJ/891/144 : CFHT dwarf satellite gal. around LV hosts (Carlsten+, 2020)
J/ApJ/907/85 : SAGA Survey. II. Satellite systems around gal. (Mao+, 2021)
J/ApJ/913/53 : Gas content of dwarf gal. within 2Mpc of MW (Putman+, 2021)
J/ApJ/922/267 : Dwarf galaxies photometry & structures (Carlsten+, 2021)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- objID Satellite galaxy objID from SAGA-II
23- 30 F8.4 deg RAdeg Right Ascension in degrees (J2000)
32- 39 F8.4 deg DEdeg Declination in Degrees (J2000)
41- 44 F4.1 Mpc Dhost [25.3/39.8] Distance of Host Galaxy from
SAGA-II
46- 49 F4.1 arcsec rcog [1/97]? Curve-of-growth radius (1)
51- 55 F5.1 --- SNnuv [0/242]? NUV signal-to-noise ratio
57 A1 --- l_NUVmag Flag on NUVmag indicating an upper limit
59- 63 F5.2 mag NUVmag [14.7/24.4]? NUV apparent AB magnitude (2)
65- 68 F4.2 mag e_NUVmag [0.01/0.6]? Error on NUVmag
70- 75 F6.2 --- SNfuv [0/729.2]? FUV signal-to-noise ratio
77 A1 --- l_FUVmag Flag on FUVmag indicating upper limit
79- 83 F5.2 mag FUVmag [14.8/25.3]? FUV apparent AB magnitude (2)
85- 88 F4.2 mag e_FUVmag [0.01/0.6]? Error on FUVmag
90 A1 --- l_logSFRnuv Flag on logSFRNUV indicating upper limit
92- 96 F5.2 [Msun/yr] logSFRnuv [-4.1/-0.27]? Log SFR estimated using
NUV luminosity (3)
98 A1 --- SF [NY] Star-forming Classification (4)
100- 131 A32 --- GALEXTile Complete GALEX Tile Name
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Note (1): Around optical centroid used to measure UV fluxes.
Note (2): Corrected for foreground extinction.
Note (3): SFRs are estimated using NUV luminosities that are not corrected for
internal infrared extinction and should be treated as estimates,
particularly for brighter (i.e. more massive) satellites.
See text for more detail.
Note (4): We define an observed satellite to be star forming either if it is
detected in the UV or if it has EW≥2 Angstroms as reported by
Mao+ (2021, J/ApJ/907/85). See Section 3.1 for full details.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 12-Feb-2024