J/MNRAS/500/1261 Resolved molecular gas in nearby galaxies (Chown+, 2021)
A new estimator of resolved molecular gas in nearby galaxies.
Chown R., Li C., Parker L., Wilson C.D., Li N., Gao Y.
<Mon. Not. R. Astron. Soc., 500, 1261-1278 (2021)>
=2021MNRAS.500.1261C 2021MNRAS.500.1261C (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Abundances, peculiar ; Extinction ;
Star Forming Region ; Infrared ; Optical ; Radio lines
Keywords: galaxies: ISM - infrared: ISM - radio lines: ISM
Abstract:
A relationship between dust-reprocessed light from recent star
formation and the amount of star-forming gas in a galaxy produces a
correlation between Wide-field Infrared Survey Explorer (WISE) 12µm
emission and CO line emission. Here, we explore this correlation on
kiloparsec scales with CO(1-0) maps from EDGE-CALIFA matched in
resolution to WISE 12µm images. We find strong CO-12µm
correlations within each galaxy and we show that the scatter in the
global CO-12µm correlation is largely driven by differences from
galaxy to galaxy. The correlation is stronger than that between star
formation rate and H2 surface densities [Σ(H2)]. We explore
multivariable regression to predict Σ(H2) in star-forming
pixels using the WISE 12µm data combined with global and resolved
galaxy properties, and provide the fit parameters for the best
estimators. We find that Σ(H2) estimators that include
Σ(12µm) are able to predict Σ(H2) more accurately
than estimators that include resolved optical properties instead of
Σ(12µm). These results suggest that 12µm emission and H2
as traced by CO emission are physically connected at kiloparsec
scales. This may be due to a connection between polycyclic aromatic
hydrocarbon emission and the presence of H2. The best
single-property estimator is log(Σ(H2)/M☉pc-2)=
(0.48±0.01)+(0.71±0.01)log(Σ(12µm)/L☉pc-2). This
correlation can be used to efficiently estimate Σ(H2) down to
at least 1M☉pc-2 in star-forming regions within nearby
galaxies.
Description:
The sample is selected from the EDGE survey (Bolatto et al.
2017ApJ...846..159B 2017ApJ...846..159B, Cat. J/ApJ/846/159). The typical angular
resolution of EDGE CO maps is 4.5arcsec, and the typical H2 surface
density sensitivity before deprojecting galaxy inclination is
11M_☉pc-2. Every EDGE galaxy has optical integral field unit
(IFU) data from CALIFA, allowing joint studies of the content and
kinematics of cold gas (H2), ionized gas, and stellar populations,
all with ∼kpc spatial resolution. We processed the CO data for all 126
EDGE galaxies, and as a starting point we selected the 95 galaxies
which had at least one detected pixel after smoothing to 6.6arcsec
resolution and regridding the moment-0 maps with 6arcsec pixels. We
then selected those galaxies with inclinations less than 75°,
leaving 83 galaxies.
We downloaded 2° by 2° cut-outs (pixel size 1.375arcsec) of
WISE 12µm (W3) flux and uncertainty for each galaxy from the
NASA/IPAC Infrared Science Archive. The background for each galaxy was
estimated using the IDL package software for source extraction
(SEXTRACTOR; Bertin & Arnouts 1996A&AS..117..393B 1996A&AS..117..393B), with default
parameters and with the corresponding W3 uncertainty map as input.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
global.dat 169 95 Global properties of the galaxies in our sample
resolved.dat 170 25321 Quantities derived from spatially-resolved
optical IFU and molecular gas maps
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See also:
J/ApJ/846/159 : Interferometric CO obs. of 126 CALIFA galaxies
(Bolatto+, 2017)
Byte-by-byte Description of file: global.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 12 A12 --- Name Galaxy name
14- 20 F7.4 [10+35W/kpc2] logSFUV ? Logarithm of the far-UV surface
density ΣFUV
22- 28 F7.4 [10+35W/kpc2] logSNUV ? Logarithm of the near-UV surface
density ΣNUV
30- 36 F7.4 [10+35W/kpc2] logSW4 ? Logarithm of the WISE W4
(22µm) surface density
ΣW4
38- 43 F6.4 [Msun/kpc2] logSM* Logarithm of the stellar mass
surface density ΣM*
45- 48 F4.2 mag AV ? Extinction measured from the
Balmer decrement
50- 53 F4.2 --- b/a ? Minor-to-major axial ratio from
CALIFA synthetic photometry
55- 60 F6.4 --- B/T ? Bulge-to-total ratio from g-band
photometry
62- 67 F6.4 [-] 12+logO/H ? Gas phase metallicity
69- 74 F6.4 --- n ? Sersic index from g-band
photometry
76- 81 F6.4 mag u-r Colour from CALIFA synthetic
photometry (SDSS filters applied
to extinction-corrected spectra)
83- 88 F6.4 [km/s] logsigma ? Logarithm of the bulge velocity
dispersion
90- 97 F8.4 [-] logcosi Logarithm of the cosine of the
inclination
99- 105 F7.4 [10+35W/kpc2] logSTIR ? Logarithm of the total-IR
(8-1000µm) surface density
ΣTIR
107- 112 F6.4 [Mpc] logDMpc Logarithm of the luminosity
distance from Bolatto et al.
(2017ApJ...846..159B 2017ApJ...846..159B,
Cat. J/ApJ/846/159)
114- 120 F7.4 [Msun/yr/kpc2] logSSFR Logarithm of the star formation
rate surface density ΣSFR
122- 130 F9.4 kpc2 Area Optical surface area (1)
132- 133 I2 --- Nx Number of pixels in the x-direction
135- 136 I2 --- Ny Number of pixels in the y-direction
138- 145 F8.4 deg RAdeg Right ascension (J2000) from LEDA
147- 153 F7.4 deg DEdeg Declination (J2000) from LEDA
155- 161 F7.4 --- xc X-coordinate (0-indexed) of center
of field
163- 169 F7.4 --- yc Y-coordinate (0-indexed) of center
of field
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Note (1): The optical surface area is 2πre2. The Σ quantities
above were divided by this number. To get total log(ΣM*) for
example, add log(Area) to log(ΣM*). The effective radius re
(half-light i-band radius) was taken from CALIFA photometry done by
Gilhuly & Courteau (2018MNRAS.477..845G 2018MNRAS.477..845G, Cat. J/MNRAS/477/845)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: resolved.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 I5 --- ID [0/25320] Pixel ID
7- 18 A12 --- Name Name of the galaxy that this pixel
belongs to
20 A1 --- fCO [0/1] Flag indicating whether the
CO measurement with the Simple
method is a detection or an upper
limit (1)
22- 23 A2 --- bpt BPT classification (2)
25- 29 F5.2 kpc2 Area Area of the pixel
31- 34 F4.2 [-] 12+logO/H ? Gas phase metallicity
36- 39 F4.2 --- alphaCO ? CO-to-H2 conversion factor
from this metallicity αCO
41 A1 --- f_logSM* [*] Flag on logSM* (3)
43- 48 F6.2 [Msun/pc2] logSM* ? Logarithm of the stellar mass
surface density ΣM*
50- 55 F6.2 [Msun/yr/kpc2] logSSFR ? Logarithm of the star formation
rate surface density ΣSFR
57- 60 F4.2 [Msun/yr/kpc2] e_logSSFR ? Error on logSSFR
62- 67 F6.2 mag AV ? Extinction measured from the
Balmer decrement
69- 72 F4.2 [K.pc2.km/s] logLCO ? Logarithm of the CO luminosity
using the Sun method, including
all pixels
74- 78 F5.2 [K.pc2.km/s] e_logLCO []? Error on logLCO
80- 83 F4.2 [K.pc2.km/s] logLCOsim ? Logarithm of the CO luminosity
using the Simple method,
including all pixels
85- 93 F9.2 [K.pc2.km/s] e_logLCOsim []? Error on logLCOsim
95- 100 F6.2 [Msun/pc2] logSH2 ? Logarithm of the H2 surface
density using the Sun method,
including all pixels, assuming
αCO=3.2
102- 106 F5.2 [Msun/pc2] e_logSH2 []? Error on logSH2
108- 113 F6.2 [Msun/pc2] logSH2sim ? Logarithm of the H2 surface
density using the Simple method,
including all pixels, assuming
αCO=3.2
115- 123 F9.2 [Msun/pc2] e_logSH2sim []? Error on logSH2sim
125- 130 F6.2 [Msun/pc2] logSH2amet ? Logarithm of the H2 surface
density using the Sun method,
only star-forming pixels,
assuming metallicity-dependent
αCO
132- 136 F5.2 [Msun/pc2] e_logSH2amet []? Error on logSH2amet
138 A1 --- f_logL12 [*] Flag on logL12 (3)
140- 143 F4.2 [Lsun] logL12 ? Logarithm of the 12µm
luminosity
145- 152 F8.2 [Lsun] e_logL12 []? Error on logL12
154 A1 --- f_logS12 [*] Flag on logS12 (3)
156- 161 F6.2 [Lsun/pc2] logS12 ? Logarithm of the 12µm surface
density
163- 170 F8.2 [Lsun/pc2] e_logS12 []? Error on logS12
--------------------------------------------------------------------------------
Note (1): Flag as follows:
0 = Detection (746/25321)
1 = Upper limit (17793/25321)
Note (2): Baldwin, Phillips, and Terlevich classification as follows:
-1 = starforming (3049/25321)
0 = composite (1641/25321)
1 = LIER (451/25321)
2 = Seyfert (149/25321)
Note (3): Flag as follows:
* = -inf value given to the flagged parameter in the original table
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 29-Sep-2023