J/A+A/667/A87 Edges of galaxies. Limits of star formation (Chamba+, 2022)
The edges of galaxies: Tracing the limits of star formation.
Chamba N., Trujillo I., Knapen J.H.
<Astron. Astrophys., 667, A87 (2022)>
=2022A&A...667A..87C 2022A&A...667A..87C (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, optical ; Galaxies, photometry ; Photometry, SDSS
Keywords: galaxies: fundamental parameters - galaxies: photometry -
galaxies: formation - methods: data analysis -
methods: observational - techniques: photometric
Abstract:
The outskirts of galaxies have been studied from multiple perspectives
for the past few decades. However, it is still unknown if all galaxies
have clear-cut edges similar to everyday objects. We address this
question by developing physically motivated criteria to define the
edges of galaxies. Based on the gas density threshold required for
star formation, we define the edge of a galaxy as the outermost radial
location associated with a significant drop in either past or ongoing
in situ star formation. We explore ∼1000 low-inclination galaxies with
a wide range in morphology (dwarfs to ellipticals) and stellar mass
(107M☉<M*<1012M☉). The location of the edges of these
galaxies (Redge) were visually identified as the outermost cutoff or
truncation in their radial profiles using deep multi-band optical
imaging from the IAC Stripe82 Legacy Project. We find this
characteristic feature at the following mean stellar mass density,
which varies with galaxy morphology: 2.9±0.10M☉/pc2 for
ellipticals, 1.1±0.04M☉/pc2 for spirals, and 0.6±0.03
M☉/pc2 for present-day star-forming dwarfs. Additionally, we
find that Redge depends on its age (colour) where bluer galaxies
have larger Redge at a fixed stellar mass. The resulting stellar
mass-size plane using Redge as a physically motivated galaxy size
measure has a very narrow intrinsic scatter (≲0.06dex). These
results highlight the importance of new deep imaging surveys to
explore the growth of galaxies and trace the limits of star formation
in their outskirts.
Description:
Edge radii and the associated surface stellar density at these
locations are provided for 180 dwarf and 444 early- and late-type
galaxies selected within the Stripe 82 foot print. For each galaxy,
the SDSS JID, right-ascension, declination coordinates, Galactic
extinction magnitude, spectral redshift, effective radius, derived
stellar masses and other radii measures from Trujillo et al.
(2020MNRAS.493...87T 2020MNRAS.493...87T, Cat. J/MNRAS/493/87) are included for
convenience. The derivation of all edge parameters and profiles
accounts for galaxy inclination using the provided axis ratios.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
dwarfs.dat 152 180 Dwarf galaxies
eltgs.dat 157 444 Early- and late-type galaxies
dprof.dat 148 8011 Surface brightness and stellar density profiles
for dwarf galaxy sample
elprof.dat 150 21629 Surface brightness and stellar density profiles
for the early- and late-type galaxies
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See also:
J/MNRAS/493/87 : 1005 galaxies with z<0.09 sample (Trujillo+, 2020)
Byte-by-byte Description of file: dwarfs.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- JID J2000 SDSS Object Identification
(JHHMMSS.ss+DDMMSS.s)
21- 29 F9.5 deg RAdeg Right Ascension (J2000)
31- 38 F8.5 deg DEdeg Declination (J2000)
40- 44 F5.3 mag Ag Galactic extinction in SDSS-g (G1)
46- 50 F5.3 mag Ar Galactic extinction in SDSS-r (G1)
52- 56 F5.3 mag Ai Galactic extinction in SDSS-i (G1)
58- 63 F6.4 --- z SDSS Spectroscopic redshift
65- 66 I2 --- TType [24] TType classification (1)
68- 71 F4.2 kpc Re Effective/half-light radius
73- 76 F4.2 kpc RhalfMass Half-mass radius
78- 82 F5.2 kpc R235i Isophotal radius at 23.5 imag/arcsec2
84- 88 F5.2 kpc RH Holmberg radius (G2)
90- 94 F5.2 kpc R1 Iso-mass radius at 1Msun/pc2
96-105 F10.8 --- q Axis ratio
107-118 F12.7 deg PA [] Position angle (G3)
120-129 F10.7 kpc Redge Edge radii
131-141 F11.9 Msun/pc2 Sigmaedge Surface stellar density at the edge (G4)
143-152 F10.7 [Msun] logMstar Log10 of stellar mass
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Note (1): TType classifications for this dwarf sample was unavailable.
NC used 24 at the time of compilation as a label.
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Byte-by-byte Description of file: eltgs.dat
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Bytes Format Units Label Explanations
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1- 20 A20 --- JID J2000 SDSS Object Identification
(JHHMMSS.ss+DDMMSS.ss)
22- 30 F9.5 deg RAdeg Right Ascension (J2000)
32- 39 F8.5 deg DEdeg Declination (J2000)
41- 45 F5.3 mag Ag Galactic extinction in SDSS-g (G1)
47- 51 F5.3 mag Ar Galactic extinction in SDSS-r (G1)
53- 57 F5.3 mag Ai Galactic extinction in SDSS-i (G1)
59- 64 F6.4 --- z SDSS Spectroscopic redshift
66- 67 I2 --- TType TType (1)
69- 73 F5.2 kpc Re Effective/half-light radius
75- 79 F5.2 kpc RhalfMass Half-mass radius
81- 85 F5.2 kpc R235i Isophotal radius at 23.5 imag/arcsec^2
87- 91 F5.2 kpc RH Holmberg radius (G2)
93- 98 F6.2 kpc R1 Iso-mass radius at 1 Msol/pc^2
100-109 F10.8 --- q Axis ratio
111-122 F12.7 deg PA [] Position angle (G3)
124-134 F11.7 kpc Redge Edge radii
136-146 F11.9 Msun/pc2 Sigmaedge Surface stellar density at the edge (G4)
148-157 F10.7 Msun logMstar Stellar mass
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Note (1): TType from Nair & Abraham (2010ApJS..186..427N 2010ApJS..186..427N, Cat. J/ApJS/186/427).
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Byte-by-byte Description of file: dprof.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 A19 --- JID J2000 SDSS Object Identification
(JHHMMSS.ss+DDMMSS.s)
21- 32 F12.9 kpc Dist Distance from galaxy centre (G5)
34- 42 F9.6 mag/arcsec2 SBg Observed surface brightness in SDSS-g (G6)
44- 55 F12.10 mag/arcsec2 e_SBg Lower error bar of SBg (G7)
57- 68 F12.10 mag/arcsec2 E_SBg ?=- Upper error bar of SBg (G7)
70- 78 F9.6 mag/arcsec2 SBr Observed surface brightness in SDSS-r (G6)
80- 92 F13.11 mag/arcsec2 e_SBr Lower error bar of SBr (G7)
94-106 F13.11 mag/arcsec2 E_SBr ?=- Upper error bar of SBr (G7)
107-121 F15.11 Msun/pc2 logSD Log10 of stellar surface density
123-134 F12.10 Msun/pc2 e_logSD ?=- Lower error bar of logSD (G8)
136-148 F13.10 Msun/pc2 E_logSD ?=- Upper error bar of logSD (G8)
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Byte-by-byte Description of file: elprof.dat
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Bytes Format Units Label Explanations
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1- 20 A20 --- JID J2000 SDSS Object Identification
(JHHMMSS.ss+DDMMSS.ss)
22- 33 F12.8 kpc Dist Distance from galaxy centre (G5)
35- 43 F9.6 mag/arcsec2 SBg Observed surface brightness in SDSS-g (G6)
45- 56 F12.10 mag/arcsec2 e_SBg Lower error bar of SBg (G7)
58- 69 F12.10 mag/arcsec2 E_SBg ?=- Upper error bar of SBg (G7)
71- 79 F9.6 mag/arcsec2 SBr Observed surface brightness in SDSS-r (G6)
81- 92 F12.10 mag/arcsec2 e_SBr Lower error bar of SBr (G7)
94-105 F12.10 mag/arcsec2 E_SBr ?=- Upper error bar of SBr (G7)
107-122 F16.12 Msun/pc2 logSD Log10 of stellar surface density
124-136 F13.10 Msun/pc2 e_logSD Lower error bar of logSD (G8)
138-150 F13.10 Msun/pc2 E_logSD ?=- Upper error bar of logSD (G8)
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Global notes:
Note (G1): Galactic extinction values were obtained using the NED calculator
(https://ned.ipac.caltech.edu/forms/calculator.html) by specifying
(RAdeg, DEdeg).
Note (G2): A proxy for Holmberg radii was measured as the isophote at
26 mag/arcsec2 in the SDSS-g band.
Note (G3): PA was measured counter-clockwise w.r.t the positive x-axis.
Note (G4): Stellar surface densities and masses were computed using
mass-to-light ratio and g-r colour relations from Roediger & Courteau
(2015MNRAS.452.3209R 2015MNRAS.452.3209R).
The values for dwarfs and late-type galaxies are inclination corrected
(see Trujillo et al., 2020MNRAS.493...87T 2020MNRAS.493...87T,, Cat. J/MNRAS/493/87)
Note (G5): The centre of each elliptical bin (semi-major axis) used to average
the flux in kpc (see paper for details). The profiles are provided up to
1.5 times Redge.
Note (G6): The profile provided is background corrected.
Use SB - A - 10log10(1+z) for the additional Galactic extinction and dimming
corrections used in the publication.
See Trujillo et al. ((2020MNRAS.493...87T 2020MNRAS.493...87T, Cat. J/MNRAS/493/87) for the
separate formula used for inclination corrections.
Note (G7): The error bars were computed by quadratically summing the standard
uncertainties from (a) averaging flux in elliptical annuli and
(b) the background subtraction.
We provide lower and upper error bars as they are non-symmetric along the
y-axis.
Note (G8): Computed using the uncertainties in surface brightness
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Acknowledgements:
Nushkia Chamba, nushkia.chamba(at)nasa.gov,
Stockholm University/NASA Ames Research Center
(End) Nushkia Chamba [Stockholm Univ.], Patricia Vannier [CDS] 12-Dec-2023