J/AJ/149/180 LITTLE THINGS dwarf galaxies mass models & properties (Oh+, 2015)
High-resolution mass models of dwarf galaxies from LITTLE THINGS.
Oh S.-H., Hunter D.A., Brinks E., Elmegreen B.G., Schruba A., Walter F.,
Rupen M.P., Young L.M., Simpson C.E., Johnson M.C., Herrmann K.A.,
Ficut-vicas D., Cigan P., Heesen V., Ashley T., Zhang H.-X.
<Astron. J. 149, 180 (2015)>
=2015AJ....149..180O 2015AJ....149..180O (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, dwarf; Abundances; H I data; Star Forming Region;
Models; Rotational velocities; Photometry, H-alpha;
Photometry, UBV; Infrared; Ultraviolet
Keywords: dark matter; galaxies: dwarf; galaxies: halos; galaxies: irregular
galaxies: kinematics and dynamics
Abstract:
We present high-resolution rotation curves and mass models of 26 dwarf
galaxies from "Local Irregulars That Trace Luminosity Extremes, The
HI Nearby Galaxy Survey" (LITTLE THINGS). LITTLE THINGS is a
high-resolution (∼6" angular; <2.6km/s velocity resolution) Very Large
Array HI survey for nearby dwarf galaxies in the local volume within
11Mpc. The high-resolution HI observations enable us to derive
reliable rotation curves of the sample galaxies in a homogeneous and
consistent manner. The rotation curves are then combined with Spitzer
archival 3.6um and ancillary optical U, B, and V images to construct
mass models of the galaxies. This high quality multi-wavelength data
set significantly reduces observational uncertainties and thus allows
us to examine the mass distribution in the galaxies in detail. We
decompose the rotation curves in terms of the dynamical contributions
by baryons and dark matter (DM) halos, and compare the latter with
those of dwarf galaxies from THINGS as well as ΛCDM Smoothed
Particle Hydrodynamic (SPH) simulations in which the effect of
baryonic feedback processes is included. Being generally consistent
with THINGS and simulated dwarf galaxies, most of the LITTLE THINGS
sample galaxies show a linear increase of the rotation curve in their
inner regions, which gives shallower logarithmic inner slopes α
of their DM density profiles. The mean value of the slopes of the 26
LITTLE THINGS dwarf galaxies is α=-0.32±0.24 which is in
accordance with the previous results found for low surface brightness
galaxies (α=-0.2±0.2) as well as the seven THINGS dwarf
galaxies (α=-0.29±0.07). However, this significantly deviates
from the cusp-like DM distribution predicted by DM-only ΛCDM
simulations. Instead our results are more in line with the shallower
slopes found in the ΛCDM SPH simulations of dwarf galaxies in which
the effect of baryonic feedback processes is included. In addition, we
discuss the central DM distribution of DDO 210 whose stellar mass is
relatively low in our sample to examine the scenario of inefficient
supernova feedback in low mass dwarf galaxies predicted from recent
ΛCDM SPH simulations of dwarf galaxies where central cusps
still remain.
Description:
We use high-resolution HI data of 26 nearby (<11Mpc) dwarf galaxies
from LITTLE THINGS to address the central DM distribution of the
galaxies. Considering the distances of the sample galaxies, the linear
resolutions of the LITTLE THINGS HI data (∼6") range from ∼26pc to
200pc with an average of 100pc which is sufficient to resolve the
inner 1kpc region of the galaxies in so far unmatched detail.
LITTLE THINGS (Hunter+2012, J/AJ/144/134) is a high-resolution (∼6"
angular; ≤2.6km/s velocity resolution) HI survey for 41 nearby
gas-rich dwarf galaxies undertaken with the NRAO VLA in the northern
sky. The LITTLE THINGS observations began with the B array 2007
December 19 and, for B array, ended 2008 February 10. C-array
observations followed in the spring of 2008 and D-array observations
in the summer of 2008. The HI observations are complemented with
other wavelength data, such as Hα, optical U, B, V, and
near-infrared (Hunter+2006, J/ApJS/162/49), archival Spitzer infrared,
and GALEX ultraviolet images as well as follow-up observations with
ALMA and Herschel. These high-quality multi-wavelength data sets
significantly reduce the observational uncertainties inherent in low
resolution data which may result in hiding the central cusps. Of the
41 galaxies, we select a sample of 26 dwarf galaxies (three of them
are also in The HI Nearby Galaxy Survey, "THINGS", from Walter+2008,
J/AJ/136/2563) which show a regular rotation pattern in their velocity
fields.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 105 26 Properties and tilted-ring parameters of the
LITTLE THINGS sample galaxies
table2.dat 171 26 Mass modeling results of the LITTLE THINGS sample
galaxies
rotdmbar.dat 63 1716 Rotation curves (DM + baryons) of the sample
galaxies (Data behind Figures 2.A, 3.A, & 4.A)
dendmbar.dat 42 1624 Density profiles (DM + baryons) of the sample
galaxies (Data behind Figures 2.B, 3.B, & 4.B)
rotdm.dat 63 1485 Rotation curves (DM only) of the sample galaxies
(Data behind Figures 2.C, 3.C, & 4.C)
dendm.dat 42 1382 Density profiles (DM only) of the sample galaxies
(Data behind Figures 2.D, 3.D, & 4.D)
nfwac.dat 38 882 The CDM NFW dark matter model rotation curves
(Data behind Figures 2, 3, and 4)
nfwbd.dat 38 875 The CDM NFW dark matter model density profiles
(Data behind Figures 2, 3, and 4)
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See also:
J/AJ/128/2170 : Hα imaging of irregular galaxies (Hunter+, 2004)
J/ApJS/162/49 : UBV imaging of irregular galaxies (Hunter+, 2006)
J/AJ/136/2563 : HI Nearby Galaxy Survey, THINGS (Walter+, 2008)
J/AJ/141/23 : HI holes in THINGS galaxies (Bagetakos+, 2011)
J/MNRAS/416/2401 : HI morphology of 28 THINGS galaxies (Holwerda+, 2011)
J/AJ/144/134 : LITTLE THINGS survey of nearby dwarf galaxies (Hunter+, 2012)
J/AJ/151/136 : LITTLE THINGS dwarf irregular gal. FUV regions (Hunter+, 2016)
J/MNRAS/466/1019 : Bright HMXBs in THINGS galaxies (Sazonov+, 2017)
J/AJ/157/241 : HI clouds in LITTLE THINGS dwarf irregular gal. (Hunter+, 2019)
J/AJ/160/66 : LITTLE THINGS catalog of HI holes in 41 galaxies (Pokhrel+, 2020)
J/AJ/161/71 : Parameters for 40 LITTLE THINGS galaxies (Hunter+, 2021)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- Name Main name of the source
10- 11 I2 h RAh Hour of right ascension (J2000) (1)
13- 14 I2 min RAm Minute of right ascension (J2000)
(1)
16- 19 F4.1 s RAs Second of right ascension (J2000)
(1)
21 A1 --- DE- Sign of declination (J2000) (1)
22- 23 I2 deg DEd Degree of declination (J2000) (1)
25- 26 I2 arcmin DEm Arcminute of declination (J2000) (1)
28- 31 F4.1 arcsec DEs Arcsecond of declination (J2000) (1)
33- 36 F4.1 Mpc Dist [0.7/10.3] Distance as given in
Hunter+2012 (J/AJ/144/134)
38- 43 F6.1 km/s Vsys [-348/589.4] Systemic velocity (1)
45- 47 F3.1 km/s e_Vsys [0.7/5.6] Vsys uncertainty (1)
49- 53 F5.1 deg PA [8.2/359.6] Average value of the
kinematic position angle (2)
55- 58 F4.1 deg e_PA [0/13.9] PA uncertainty (2)
60- 63 F4.1 deg i [22.6/82.5] Average value of the
kinematic inclination (1)
65- 68 F4.1 deg e_i [0/15.6] i uncertainty (1)
70- 74 F5.1 mag VMag [-18.2/-10.9] Absolute V magnitude
as given in Hunter+2012
(J/AJ/144/134)
76- 78 F3.1 [-] Ab(O/H) [7.2/8.7] 12+log(O/H) ; Oxygen
abundance taken from the literature
as compiled in Hunter+2012
(J/AJ/144/134)
80- 83 F4.2 [-] e_Ab(O/H) [0.01/0.2]? Ab(O/H) uncertainty
85- 89 F5.2 Msun/yr/kpc2 log(SFR)Ha [-4.1/0.19]? Hα star
formation rates normalized to the
area (πR2 where R is the disk
scale length) as given in
Hunter+2004 (J/AJ/128/2170)
91- 94 F4.2 Msun/yr/kpc2 e_log(SFR)Ha [0.01/0.07]? log(SFR)Ha uncertainty
96- 100 F5.2 Msun/yr/kpc2 log(SFR)FUV [-3.21/-0.01]? GALEX FUV star
formation rates normalized to the
area (πR2 where R is the disk
scale length) as given in
Hunter+2010 (2010AJ....139..447H 2010AJ....139..447H)
102- 105 F4.2 Msun/yr/kpc2 e_log(SFR)FUV [0/0.06]? log(SFR)FUV uncertainty
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Note (1): Derived from the tilted-ring analysis described in Section 3.1.1.
Note (2): Derived from the tilted-ring analysis described in Section 3.1.1.
PA is the angle measured counter-clockwise from the north direction in the
sky to the major axis of the receding half of the galaxy.
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Byte-by-byte Description of file:table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- Name Main name of the source
10- 13 F4.2 kpc Rmax [0.31/9.81] Radius where the
outermost part of the rotation curve
is measured
15- 18 F4.2 kpc R0.3 [0.2/5.43] Radius where the
logarithmic slope of the total
rotation curve dlog(V)/dlog(R)=0.3
20- 24 F5.1 km/s V(Rmax) [12/125.5] Rotation velocity
(asymmetric drift corrected) at Rmax
26- 30 F5.1 km/s Viso(Rmax) [11.3/130.2] Rotation velocity of
the best fitted pseudo-isothermal
halo model at Rmax
32- 36 F5.1 --- Rmax/HI [6/103.8] Ratio of Rmax to HI beam
size
38- 41 F4.2 kpc z0 [0.07/0.48]? Vertical scale height
of the stellar disk
43- 46 F4.1 --- c [-0.4/25] Concentration parameter
48- 53 F6.1 --- e_c [0.2/1503.4]? c uncertainty (1)
55- 58 F4.1 --- cM07 [8.1/18.6] Concentration parameter
derived using an empirical
relationship between c and V200 as
given by McGaugh+2007
(2007ApJ...659..149M 2007ApJ...659..149M)
60- 65 F6.1 km/s V200 [5.4/2290.8] Rotation velocity for a
NFW model (2)
67- 73 F7.1 km/s e_V200 [0.9/48442.1]? V200 uncertainty (1)
75- 79 F5.1 km/s V200M07 [12.4/598.2]? V200 values fitted
after fixing c to cM07 assuming a
"minimum disk" (2)
81- 84 F4.1 km/s e_V200M07 [0.2/30.4]? V200M07 uncertainty
86- 89 F4.2 kpc Rc [0.15/8.4] Core radius of
pseudo-isothermal model
(Begeman+1991, 1991MNRAS.249..523B 1991MNRAS.249..523B)
91- 95 F5.2 kpc e_Rc [0.01/12.2] Rc uncertainty
97- 103 F7.2 10-3Msun/pc3 rho0 [8.19/2132.4] Core density of
pseudo-isothermal model
(Begeman+1991, 1991MNRAS.249..523B 1991MNRAS.249..523B)
105- 110 F6.2 10-3Msun/pc3 e_rho0 [0.77/381.14] rho0 uncertainty
112- 116 F5.2 --- alphamin [-1.25/1.16] Logarithmic inner slope
of the total matter (DM
halo+baryons) density profiles (3)
118- 122 F5.2 --- e_alphamin [0.01/1.22] alphamin uncertainty
124 A1 --- f_alphamin The dynamical contribution by the
stellar component is included in the
DM density profile as no Spitzer
3.6mum image is available for this
galaxy
126- 130 F5.2 --- alpha3.6 [-1.25/0.97] Logarithmic inner slope
of the DM density profiles (3)
132- 136 F5.2 --- e_alpha3.6 [0.01/0.92] alpha3.6 uncertainty
138 A1 --- f_alpha3.6 The dynamical contribution by the
stellar component is included in the
DM density profile as no Spitzer
3.6mum image is available for this
galaxy
140- 145 F6.2 10+7Msun Mgas [0.14/132.52] Gas mass (4)
147- 151 F5.2 10+7Msun MstarK [0.04/20.7]? Stellar mass derived
from the kinematic analysis (5)
153- 157 F5.2 10+7Msun MstarSED [0.06/46.7]? Stellar mass derived
using a spectral energy distribution
fitting technique in Zhang+2012
(2012AJ....143...47Z 2012AJ....143...47Z)
159- 163 F5.3 [Msun] log(Mdyn) [6.9/9.93] Log of dynamical mass
measured using Viso(Rmax) and Rmax
165- 171 F7.3 [Msun] log(M200) [8.7/510.2] CDM halo mass estimated
from V200M07 (6)
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Note (1): A null value means that the error is unphysically large.
Note (2): NFW model from Navarro+1995 (1995MNRAS.275...56N 1995MNRAS.275...56N) &
Navarro+1996b (1996ApJ...462..563N 1996ApJ...462..563N). See Section 3.4.
Note (3): Measured in Section 4.2.
Note (4): Derived in Section 3.2.
Note (5): Derived in Section 3.3.
Note (6): Using Equation 3 from Oh+2011a (2011AJ....142...24O 2011AJ....142...24O). See Section 3.4.
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Byte-by-byte Description of file: rotdmbar.dat rotdm.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Name Galaxy identifier
10- 14 A5 --- Type Data type (1)
16- 23 F8.6 kpc R0.3 Radius where the logarithmic slope of the total
rotation curve dlog(V)/dlog(R)=0.3
25- 34 F10.6 km/s V0.3 Rotation velocity at R0.3
36- 44 F9.6 --- R Radius scaled by R0.3
46- 54 F9.6 --- V Velocity scaled by V0.3
56- 63 F8.6 --- e_V Uncertainty in V
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Note (1): Data type as follows:
Data = The scaled total rotation velocity which is corrected
for the asymmetric drift.
Model = Pseudo-isothermal halo model fit to the total rotation velocity.
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Byte-by-byte Description of file: dendmbar.dat dendm.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Name Galaxy identifier
10- 14 A5 --- Type Data type (1)
16- 23 F8.5 [-] R Log radius scaled by R0.3
25- 35 E11.4 [-] rho Log density scaled by ρ0.3
37- 42 F6.4 [-] e_rho Uncertainty in rho
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Note (1): Data type as follows:
Data = The scaled total rotation velocity which is corrected
for the asymmetric drift.
Model = Pseudo-isothermal halo model fit to the total rotation velocity.
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Byte-by-byte Description of file: nfwac.dat
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Bytes Format Units Label Explanations
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1- 6 F6.3 --- c Model concentration parameter
8- 10 I3 km/s V200 Model rotation velocity at R200; see Equ. 7
12- 20 F9.6 --- R Model radius scaled by R0.3
22- 29 F8.6 --- V Model rotation velocity scaled by V0.3 (1)
31- 38 F8.6 --- e_V Uncertainty in V
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Note (1): See Equation 7.
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Byte-by-byte Description of file: nfwbd.dat
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Bytes Format Units Label Explanations
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1- 6 F6.3 --- c Model concentration parameter
8- 10 I3 km/s V200 Model rotation velocity at R200
12- 19 F8.5 [-] R Model log radius scaled by R0.3
21- 31 E11.4 [-] rho Model log density scaled by ρ0.3 (1)
33- 38 F6.4 [-] e_rho Uncertainty in rho
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Note (1): See Equation 6.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Robin Leichtnam [CDS] 10-Mar-2026