J/AJ/151/145 Dwarf galaxies surface brightness profiles. II. (Herrmann+, 2016)
Surface brightness profiles of dwarf galaxies. II. Color trends and mass
profiles.
Herrmann K.A., Hunter D.A., Elmegreen B.G.
<Astron. J., 151, 145-145 (2016)>
=2016AJ....151..145H 2016AJ....151..145H (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, photometry ; Morphology
Keywords: galaxies: dwarf - galaxies: fundamental parameters -
galaxies: irregular - galaxies: photometry - galaxies: structure
Abstract:
In this second paper of a series, we explore the B-V, U-B, and FUV-NUV
radial color trends from a multi-wavelength sample of 141 dwarf disk
galaxies. Like spirals, dwarf galaxies have three types of radial
surface brightness profiles: (I) single exponential throughout the
observed extent (the minority), (II) down-bending (the majority), and
(III) up-bending. We find that the colors of (1) Type I dwarfs
generally become redder with increasing radius, unlike spirals which
have a blueing trend that flattens beyond ∼1.5 disk scale lengths, (2)
Type II dwarfs come in six different "flavors", one of which mimics
the "U" shape of spirals, and (3) Type III dwarfs have a stretched "S"
shape where the central colors are flattish, become steeply redder
toward the surface brightness break, then remain roughly constant
beyond, which is similar to spiral Type III color profiles, but
without the central outward bluing. Faint (-9>MB>-14) Type II dwarfs
tend to have continuously red or "U" shaped colors and steeper
color slopes than bright (-14>MB>-19) Type II dwarfs, which
additionally have colors that become bluer or remain constant with
increasing radius. Sm dwarfs and BCDs tend to have at least some blue
and red radial color trend, respectively. Additionally, we determine
stellar surface mass density (Σ) profiles and use them to show
that the break in Σ generally remains in Type II dwarfs (unlike
Type II spirals) but generally disappears in Type III dwarfs (unlike
Type III spirals). Moreover, the break in Σ is strong,
intermediate, and weak in faint dwarfs, bright dwarfs, and spirals,
respectively, indicating that Σ may straighten with increasing
galaxy mass. Finally, the average stellar surface mass density at the
surface brightness break is roughly 1-2M☉pc-2 for Type II
dwarfs but higher at 5.9M☉pc-2 or 27M☉pc-2 for
Type III BCDs and dIms, respectively.
Description:
Our galaxy sample (see Table1) is derived from the survey of nearby
(>30Mpc) late-type galaxies conducted by Hunter & Elmegreen 2006 (cat.
J/ApJS/162/49). The full survey includes 94 dwarf Irregulars (dIms),
26 Blue Compact Dwarfs (BCDs), and 20 Magellanic-type spirals (Sms).
The 141 dwarf sample presented in the first paper of the present
series (Paper I; Herrmann et al. 2013, Cat. J/AJ/146/104) contains one
fewer Sm galaxy and two additional dIm systems than the original
survey.
A multi-wavelength data set has been assembled for these galaxies. The
data include Hα images (129 galaxies with detections) to trace
star formation over the past 10Myr (Hunter & Elmegreen 2004, Cat.
J/AJ/128/2170) and satellite UV images (61 galaxies observed) obtained
with the Galaxy Evolution Explorer (GALEX) to trace star formation
over the past ∼200Myr. The GALEX data include images from two
passbands with effective wavelengths of 1516Å (FUV) and 2267Å
(NUV) and resolutions of 4'' and 5.6'', respectively. Three of the
galaxies in our sample with NUV data do not have FUV data. To trace
older stars we have UBV images, which are sensitive to stars formed
over the past 1Gyr for on-going star formation, and images in at least
one band of JHK for 40 galaxies in the sample, which integrates the
star formation over the galaxy's lifetime. Note that nine dwarfs are
missing UB data and three more are missing U-band data. In addition we
made use of 3.6µm images (39 galaxies) obtained with the Infrared
Array Camera (IRAC) in the Spitzer archives also to probe old stars.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 87 141 Galaxy sample and color profile classifications
table2.dat 112 319 Parameters of single and/or broken fits to
color profiles (functions of radius in kiloparsecs)
table3.dat 101 80 *Parameters of fits to average profiles
(functions of scaled radii)
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Note on table3.dat: For broken and Type I fits, the radii have been scaled by
the surface brightness break location and scale length, respectively.
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See also:
J/MNRAS/441/1992 : Galaxies with disc breaks in S4G and NIRS0S (Laine+, 2014)
J/ApJ/771/59 : Surface brightness of S4G face-on galaxies
(Munoz-Mateos+, 2013)
J/AJ/146/104 : Dwarf gal. surface brightness profiles. I. (Herrmann+, 2013)
J/AJ/144/134 : LITTLE THINGS survey of dwarf galaxies (Hunter+, 2012)
J/AJ/142/145 : Outer disks of S0-Sb gal. II. (Gutierrez+, 2011)
J/AJ/136/2563 : HI Nearby Galaxy Survey, THINGS (Walter+, 2008)
J/ApJ/684/1026 : Photometric profiles from GOODS data (Azzollini+, 2008)
J/ApJS/162/49 : UBV imaging of irregular galaxies (Hunter+, 2006)
J/AJ/128/2170 : Hα imaging of irregular galaxies (Hunter+, 2004)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- Name Galaxy identifier
14- 16 A3 --- MT Morphological Hubble type (BCD, Im, or Sm) (1)
18- 23 F6.2 mag BMag [-19/-9.11]? Absolute B band magnitude (2)
25- 28 F4.2 --- b/a [0.21/1] Minor-to-Major axis ratio (3)
30- 41 A12 --- Type Type of radial surface brightness profile (I, II,
FI, or III) (4)
43- 48 A6 --- CType1 The (B-V) color profile classification (G1)
50- 52 A3 --- f_CType1 Outlier/Short flag for CType1 (O, S, or O/R) (5)
54- 60 A7 --- CType2 The (U-B) color profile classification (G1)
62- 66 A5 --- f_CType2 Outlier/Short flag for CType1 (O, S, O/R,
or O/R,S) (5)
68- 73 A6 --- CType3 The (FUV-NUV) color profile classification (G1)
75- 77 A3 --- f_CType3 Outlier/Short flag for CType3 (O, S, or O/R) (5)
79- 82 A4 --- Note Additional notes (6)
84- 85 A2 --- LT [LT] Member of LITTLE THINGS survey (Hunter et
al. 2012, Cat. J/AJ/144/134)
87 A1 --- T [T] Member of THINGS survey (Walter et al. 2008,
Cat. J/AJ/136/2563)
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Note (1):
From de Vaucouleurs et al. 1991 (RC3; cat. VII/155) (if no type is
given there, we used types from NED):
* BCD = Blue Compact Dwarf;
* Im = Dwarf irregular;
* Sm = Magellanic-type spiral.
Note (2): Calculated from Hunter & Elmegreen 2006 (cat. J/ApJS/162/49) using
distances from Paper I (Herrmann et al. 2013, Cat. J/AJ/146/104). Blanks
mean no BMag data.
Note (3): From Hunter & Elmegreen 2006 (cat. J/ApJS/162/49) used for inclination
corrections assuming b/a0=0.3.
Note (4):
From Paper I (Herrmann et al. 2013, Cat. J/AJ/146/104).
* I = Single exponential throughout the observed extent (the minority).
We find that the colors of Type I dwarfs generally become redder
with increasing radius, unlike spirals which have a blueing trend
that flattens beyond ∼1.5 disk scale lengths;
* II = Down-bending (the majority). Type II dwarfs come in six different
"flavors", one of which mimics the "U" shape of spirals;
* FI = Dwarfs have a special case of Type II profiles unobserved in
spirals: FI, flat or even increasing intensity with increasing
radius in the central regions before falling off beyond some break;
* III = Up-bending. Type III dwarfs have a stretched "S" shape where the
central colors are flattish, become steeply redder toward the
surface brightness break, then remain roughly constant beyond,
which is similar to spiral Type III color profiles, but without the
central outward bluing.
Galaxies with two breaks are listed as "inner type + outer type" and ones
with different types depending on wavelength are generally listed blue to
red separated by a "/".
Note (5): Codes for galaxy not used in the averaging analysis:
O = Color profile outlier from the common color trend;
S = Too short profile.
Note (6): Notes defined as follows:
PM = Peculiar Morphology;
VO = V-band only;
B = Barred.
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- Name Galaxy identifier (1)
14- 20 A7 --- Color Color used (U-B, B-V, or FUV-NUV)
22- 26 F5.2 kpc Rbrk [0.11/10.32] Surface brightness profile
break location or scale length (2)
28- 34 A7 --- CType Color profile flavor (G1)
36- 41 F6.3 mag/arcsec2/kpc mI [-0.41/1.95]? Single line fit color slope
43- 47 F5.3 mag/arcsec2/kpc e_mI [0.01/4.09]? Uncertainty in mI
49- 54 F6.3 mag/arcsec2 bI [-0.95/0.71]? Single line color fit y
intercept (3)
56- 60 F5.3 mag/arcsec2 e_bI [0.018/0.8]? Uncertainty in bI
62- 67 F6.3 mag/arcsec2/kpc mi [-4.32/1.38]? Inner fit color slope
69- 73 F5.3 mag/arcsec2/kpc e_mi [0.001/5.05]? Uncertainty in mi
75- 80 F6.3 mag/arcsec2 bi [-0.86/1.19]? Inner color fit y
intercept (3)
82- 86 F5.3 mag/arcsec2 e_bi [0.001/0.7]? Uncertainty in bi
88- 93 F6.3 mag/arcsec2/kpc mo [-2.12/8.5]? Outer fit color slope
95- 99 F5.3 mag/arcsec2/kpc e_mo [0/6.75]? Uncertainty in mo
101-106 F6.3 mag/arcsec2 bo [-2.62/3.56]? Outer color fit y
intercept (3)
108-112 F5.3 mag/arcsec2 e_bo [0.001/3.3]? Uncertainty in bo
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Note (1):
The ambiguous color profiles fit by two lines ("broken-by-default")
and one with all the ambiguous color profiles fit by a single line
("single-by-default"). The program classified each color profile according
to the fitted trends. Single profiles were either:
* (1) Flat: F, arbitrarily set by the absolute value of the slope being
less than 0.02mag/arsec2/kpc;
* (2) Red: R, for positive slope;
* (3) Blue: B, for negative slope.
Each broken segment was also classified as B, R, or F, for the eight
possible broken trends: BB, BR, BF, RB, RR, RF, FB, and FR.
Note (2): Surface brightness profile break location (for Type II and III
profiles) or scale length (for Type I profiles) in kpc. For each color, the
provided measurement is for the redder band (V for B-V, B for U-B, and NUV
for FUV-NUV).
Note (3): Recall that the color profile fits for Type III dwarfs with the
characteristic horizontally stretched "S" color shape (SI or SB) were fit
by natural cubic splines to capture the curvature in the color profile
shape. Consequently, the single and broken color fits were not very
important in this analysis, but both are provided in this table.
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- CType Color profile flavor (1)
9- 19 A11 --- Profile Profile type (U-B, B-V, µV, log Σ,
or FUV-NUV)
21- 23 A3 --- Def Default type (Brk, Sgl, or 2B) (2)
25- 30 F6.3 --- mI [-1.35/1.11]? Single line fit slope (3)
32- 36 F5.3 --- e_mI [0.002/0.19]? Uncertainty in mI
38- 43 F6.3 --- bI [-0.56/22.45]? Single line fit y intercept (3)
45- 49 F5.3 --- e_bI [0/0.32]? Uncertainty in bI
51- 56 F6.3 --- mi [-2.11/5.3]? Inner fit slope (3)
58- 62 F5.3 --- e_mi [0/0.06]? Uncertainty in mi
64- 69 F6.3 --- bi [-0.58/23.86]? Inner fit y intercept (3)
71- 75 F5.3 --- e_bi [0/0.03]? Uncertainty in bi
77- 82 F6.3 --- mo [-1.71/4.76]? Outer fit slope (3)
84- 88 F5.3 --- e_mo [0/0.09]? Uncertainty in mo
90- 95 F6.3 --- bo [-0.69/22.43]? Outer fit y intercept(3)
97-101 F5.3 --- e_bo [0/0.12]? Uncertainty in bo
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Note (1): As determined in this study, for dwarfs as well as the color trends
found in spirals from Bakos et al. (2008ApJ...683L.103B 2008ApJ...683L.103B). For broken and
Type I fits, the radii have been scaled by the surface brightness break
location and scale length, respectively. Note that in some instances
(II(sp), IIBR, III(SB), and III(SI)) logΣ is fairly well fit by a
single line. The parameters for both the best single and broken fits are
listed here in these four cases. Additionally, only the two break (2B, but
three segments) fits are shown in Figures 1 and 2 for the B-V, U-B, and
FUV-NUV color profiles for Type III BCDs and dIms (and spirals in B-V
only), but broken fits with only two segments are also listed here.
Note (2):
The default types are defined as below:
* Brk = Broken-by-default sample;
* Sgl = Single-by-default sample;
* 2B = A fit with two breaks.
The parameters for the inner, middle, and outer segments are given in the
I, i, and o columns, respectively.
Note (3): In mag/arsec2 for a surface brightness or color fit or in
log10(MSun/pc2) for surface mass density.
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Global Notes:
Note (G1): From this study. The presence of a "/" indicates an ambiguous
profile; the first classification was used in the broken-by-default
analysis and the second in the single-by-default analysis. The parameters
for the best single and broken fits are listed in Table2 for these
ambiguous color trends.
B = Continuous blue single trend;
R = Continuous red single trend;
F = Continuous flat single trend;
FB = Flat then blue broken trend;
RB = Red then blue broken trend
BB = Blue then blue broken trend;
BR = Blue then red broken trend;
RR = Red then red broken trend;
RF = Red then flat broken trend;
FR = Flat then red broken trend;
BF = Blue then flat broken trend;
SI = Dwarf irregular (Im) with S shape;
SB = Blue Compact Dwarf (BCD) with S shape.
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History:
From electronic version of the journal
References:
Herrmann et al., Paper I 2013AJ....146..104H 2013AJ....146..104H, Cat. J/AJ/146/104
(End) Prepared by [AAS]; Sylvain Guehenneux [CDS] 27-Jul-2016