J/ApJ/858/90 Radial profiles of 5 nearby galaxies (Gallagher+, 2018)
Dense gas, dynamical equilibrium pressure, and star formation in nearby
star-forming galaxies.
Gallagher M.J., Leroy A.K., Bigiel F., Cormier D., Jimenez-Donaire M.J.,
Ostriker E., Usero A., Bolatto A.D., Garcia-Burillo S., Hughes A.,
Kepley A.A., Krumholz M., Meidt S.E., Meier D.S., Murphy E.J., Pety J.,
Rosolowsky E., Schinnerer E., Schruba A., Walter F.
<Astrophys. J., 858, 90 (2018)>
=2018ApJ...858...90G 2018ApJ...858...90G
ADC_Keywords: Galaxies, nearby; Interferometry; Radio lines; Infrared sources;
Interstellar medium
Keywords: galaxies: ISM ; galaxies: star formation ; radio lines: ISM
Abstract:
We use new ALMA observations to investigate the connection between
dense gas fraction, star formation rate (SFR), and local environment
across the inner region of four local galaxies showing a wide range of
molecular gas depletion times. We map HCN(1-0), HCO+(1-0), CS(2-1),
13CO(1-0), and C18O(1-0) across the inner few kiloparsecs of each
target. We combine these data with short-spacing information from the
IRAM large program EMPIRE, archival CO maps, tracers of stellar
structure and recent star formation, and recent HCN surveys by Bigiel+
(2016ApJ...822L..26B 2016ApJ...822L..26B) and Usero+ (2015AJ....150..115U 2015AJ....150..115U). We test the
degree to which changes in the dense gas fraction drive changes in the
SFR. IHCN/ICO (tracing the dense gas fraction) correlates strongly
with ICO (tracing molecular gas surface density), stellar surface
density, and dynamical equilibrium pressure, PDE (Elmegreen
1989ApJ...338..178E 1989ApJ...338..178E). Therefore, IHCN/ICO becomes very low and HCN
becomes very faint at large galactocentric radii, where ratios as low
as IHCN/ICO∼0.01 become common. The apparent ability of dense gas
to form stars, ΣSFR/Σdense (where Σdense is
traced by the HCN intensity and the star formation rate is traced by a
combination of Hα and 24µm emission), also depends on
environment. ΣSFR/Σdense decreases in regions of high
gas surface density, high stellar surface density, and high PDE.
Statistically, these correlations between environment and both
ΣSFR/Σdense and IHCN/ICO are stronger than that
between apparent dense gas fraction (IHCN/ICO) and the apparent
molecular gas star formation efficiency ΣSFR/Σmol. We
show that these results are not specific to HCN.
Description:
As part of ALMA's Cycle 2 campaign, we observed HCN(1-0) (88.63GHz),
HCO+(1-0) (89.19GHz), CS(2-1) (97.97GHz), 13CO(1-0) (110.20GHz),
and C18O(1-0) (109.78GHz) in four galaxies using ALMA's main array
of 12m antennas.
We combined our 12m HCN, HCO+, 13CO, and C18O data with
single-dish maps obtained as part of the IRAM EMPIRE Survey (Bigiel+
2016ApJ...822L..26B 2016ApJ...822L..26B ; Cormier+ 2018MNRAS.475.3909C 2018MNRAS.475.3909C ;
M. Jimenez Donaire+ 2018, in preparation).
See Section 2.1.
We also use 12CO(1-0) (115.27GHz) emission to trace the overall
molecular gas reservoir. We draw these maps from literature data;
see Section 2.2.
We compare our observations to 3.6um maps, which are dominated by
light from old stars. We use maps obtained by Spitzer, mostly as part
of SINGS (Kennicutt+ 2003PASP..115..928K 2003PASP..115..928K), and processed as part of
the S4G survey (Sheth+ 2010, J/PASP/122/1397).
See section 2.6.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 81 5 Targets observed
suppmat.dat 470 97 Radial profile data table (Appendix C)
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See also:
B/iram : IRAM Observation Logs (IRAM 1991-2015)
VI/139 : Herschel Observation Log (Herschel Science Centre, 2013)
J/ApJ/671/333 : Aperture photometry in NGC 5194 (Kennicutt+, 2007)
J/AJ/136/2782 : Star formation efficiency in nearby galaxies (Leroy+, 2008)
J/AJ/136/2563 : HI Nearby Galaxy Survey, THINGS (Walter+, 2008)
J/ApJS/184/1 : Molecular clouds in the LMC by NANTEN. II. (Kawamura+, 2009)
J/ApJ/706/599 : Hα and UV SFR in the local volume (Lee+, 2009)
J/ApJ/701/1965 : Radial dust properties of SINGS galaxies (Munoz-Mateos+, 2009)
J/ApJ/714/1256 : Far-IR star formation rate indicators (Calzetti+, 2010)
J/ApJ/723/1019 : Galactic SFR and gas surface densities (Heiderman+, 2010)
J/PASP/122/1397 : Spitzer Survey of Stellar Structure in Gal. (Sheth+, 2010)
J/AJ/146/150 : Veloc. dispersions of 12 nearby galaxies (Caldu-Primo+, 2013)
J/ApJ/771/59 : Surface brightness of S4G face-on gal. (Munoz-Mateos+, 2013)
J/A+A/584/A91 : Cat. of dense cores in Aquila from Herschel (Konyves+, 2015)
J/ApJ/846/159 : Interferometric CO obs. of 126 CALIFA gal. (Bolatto+, 2017)
J/ApJ/846/71 : M51 ISM structures from the CO maps of PAWS (Leroy+, 2017)
J/ApJ/835/217 : Density distributions for mm-wave line ratios (Leroy+, 2017)
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- --- [NGC]
5- 8 I4 --- NGC NGC number of the galaxy
10- 12 A3 --- n_NGC 30m: Observed with the IRAM 30m (1)
14- 24 F11.7 deg RAdeg [160.9/202.5] Right ascension (J2000) (2)
26- 35 F10.7 deg DEdeg [11.7/47.2] Declination (J2000) (2)
37- 47 A11 --- Morph Morphology from NED
49- 52 F4.1 deg Inc [22/62] Inclination (3)
54- 58 F5.1 deg PA [7.5/192] Position angle, north through east
60 A1 --- r_PA Source for orientation parameters (4)
62- 66 F5.2 Mpc Dist [7.6/14.4] Adopted distance of the galaxy
from Kennicutt+ (2011PASP..123.1347K 2011PASP..123.1347K)
68- 70 I3 pc Beam [295/636] Linear beam (5)
72- 81 A10 kpc FOV Field of view across the dense gas maps at
the distance of the galaxy without accounting
for inclination
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Note (1): Data from Bigiel+ (2016ApJ...822L..26B 2016ApJ...822L..26B); see that paper for
more details.
Note (2): Adopted center of the galaxy from the NASA Extragalactic Database,
which draws key information from RC3 (de Vaucouleurs+ 1991, VII/155).
Note (3): Inclination used to construct the radial profiles and correct surface
densities for projection.
Note (4): Reference code as follows:
a = Dicaire et al. (2008MNRAS.385..553D 2008MNRAS.385..553D);
b = de Blok et al. (2008AJ....136.2648D 2008AJ....136.2648D);
c = Boissier et al. (2003MNRAS.346.1215B 2003MNRAS.346.1215B);
d = Munoz-Mateos et al. (2009, J/ApJ/701/1965);
e = Colombo et al. (2014ApJ...784....4C 2014ApJ...784....4C).
Note (5): Linear scale in pc of the FWHM of the beam used in this analysis.
This is 8" at the distance of the galaxy for the first four targets
and 30"=1.1kpc for NGC 5194 (Bigiel+ 2016ApJ...822L..26B 2016ApJ...822L..26B).
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Byte-by-byte Description of file: suppmat.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- NGC NGC number of the galaxy
6- 10 F5.3 kpc Rad [0.03/6] Inner radius of ring
12- 18 F7.3 K.km/s I-CO [0/139] Average intensity, CO 1-0
20- 24 F5.3 K.km/s e_I-CO [0/2.1]?=-999 Uncertainty, rms,
in I-CO
26- 32 F7.4 K.km/s I-HCN [-0.008/9.6] Average intensity,
HCN 1-0
34- 39 F6.4 K.km/s e_I-HCN [0/0.2]?=-999 Uncertainty, rms,
in I-HCN
41- 49 F9.4 K.km/s I-CS [-0.07/3]?=-999 Average intensity,
CS 2-1
51- 59 F9.4 K.km/s e_I-CS [0/0.2]?=-999 Uncertainty, rms,
in I-CS
61- 67 F7.4 K.km/s I-HCO+ [-0.03/6.1] Average intensity,
HCO+ 1-0
69- 74 F6.4 K.km/s e_I-HCO+ [0/0.2]?=-999 Uncertainty, rms,
in I-HCO+
76- 82 F7.4 K.km/s I-13CO [0/12] Average intensity, 13CO 1-0
84- 89 F6.4 K.km/s e_I-13CO [0/0.2]?=-999 Uncertainty, rms,
in 13CO
91- 99 F9.4 K.km/s I-C18O [-0.08/2.2]?=-999 Average intensity,
C18O 1-0
101-109 F9.4 K.km/s e_I-C18O [0/0.2]?=-999 Uncertainty, rms,
in I-C18O
111-118 F8.5 MJy/sr I-3.6um [0.2/14.4] Average intensity, 3.6um
120-126 F7.5 MJy/sr e_I-3.6um [0.0001/0.005] Uncertainty, rms,
in I-3.6um
128-135 F8.4 MJy/sr I-24um [0.1/227] Average intensity, 24um
137-142 F6.4 MJy/sr e_I-24um [0.0009/0.03] Uncertainty, rms,
in I-24um
144-150 F7.2 MJy/sr I-70um [2.9/2571] Average intensity, 70um
152-155 F4.2 MJy/sr e_I-70um [0.02/1] Uncertainty, rms, in I-70um
157-166 E10.4 MJy/sr I-FUV [0.001/0.5] Average intensity, FUV
168-175 E8.2 MJy/sr e_I-FUV [/0.0003] Uncertainty, rms, in I-FUV
177-186 E10.4 mW/m2/sr I-Ha [1.7e-06/8.5e-05] Average intensity,
Hα, erg/s/cm2/sr (1)
188-195 E8.2 mW/m2/sr e_I-Ha Uncertainty, rms, in I-Ha
197-206 E10.4 cm-3/K PDE [2942/1.9e+07] Dynamical equilibrium
pressure
208-218 E11.4 cm-3/K e_PDE [345/1.5e+06]?=-9.99 Uncertainty,
rms, in PDE
220-225 F6.1 Msun/pc2 Sd* [78.8/5043] Stellar surface denisty
227-230 F4.1 Msun/pc2 e_Sd* [0/37] Uncertainty, rms, in Sd*
232-241 E10.4 W/kpc2 TIR70 [5.2e+33/1.7e+36] Total infrared
average intensity from 70um
243-250 E8.2 W/kpc2 e_TIR70 [8.6e+32/2.2e+33] Uncertainty, rms,
in TIR70
252-259 E8.2 W/kpc2 TIR24 [2e+33/1.4e+36] Total infrared
average intensity from 24um
261-268 E8.2 W/kpc2 e_TIR24 [6.5e+33/2.3e+34] Uncertainty, rms,
in TIR24
270-275 F6.2 Msun/pc2 Sd-gas [0.6/602]?=-999 Total (HI+molecular)
gas surface density
277-283 F7.2 Msun/pc2 e_Sd-gas [0.1/53]?=-999 Uncertainty, rms,
in Sd-gas
285-290 F6.2 Msun/pc2 Sd-mol [0/595] Molecular gas surface density
292-295 F4.2 Msun/pc2 e_Sd-mol [0/9] Uncertainty, rms, in Sd-mol
297-302 F6.3 Msun/pc2 Sd-dense [-0.08/96] Dense gas surface density
304-308 F5.3 Msun/pc2 e_Sd-dense [0/1.1] Uncertainty, rms, in Sd-dense
310-319 E10.4 Msun/pc2/yr SFR-TIR70um [2e-09/6.6e-07] Star formation rate
TIR_70
321-328 E8.2 Msun/pc2/yr e_SFR-TIR70um Uncertainty, rms, in SFR-70um
330-339 E10.4 Msun/pc2/yr SFR-TIR24um [8.3e-10/5.5e-07] Star formation
rate TIR_24
341-349 E9.3 Msun/pc2/yr e_SFR-TIR24um [2.5e-09/9e-09] Uncertainty, rms,
in SFR-24um
351-360 E10.4 Msun/pc2/yr SFR-Ha+24um [1.4e-09/6e-07] Star formation rate
Halpha+24um
362-369 E8.2 Msun/pc2/yr e_SFR-Ha+24um [1e-11/2e-09] Uncertainty, rms,
in SFR-Ha+24um
371-380 E10.4 Msun/pc2/yr SFR-FUV+24um [5.6e-10/7.6e-07] Star formation rate
FUV+24um
382-389 E8.2 Msun/pc2/yr e_SFR-FUV+24um Uncertainty, rms, in SFR-FUV+24um
391-400 E10.4 Msun/pc2 Sd-HI [0.01/2.4e+19] HI gas surface density
402-410 E9.4 Msun/pc2 e_Sd-HI Uncertainty, rms, in Sd-HI
412-421 E10.4 Msun/pc2/yr SFR-24um [4.3e-10/7.3e-07] Star formation
rate 24um only
423-430 E8.2 Msun/pc2/yr e_SFR-24um Uncertainty, rms, in SFR-24um
432-441 E10.4 Msun/pc2/yr SFR-FUV [9.8e-11/3.5e-08] Star formation
rate FUV only
443-450 E8.2 Msun/pc2/yr e_SFR-FUV Uncertainty, rms, in SFR-FUV
452-461 E10.4 Msun/pc2/yr SFR-Ha [1e-09/5.4e-08] Star formation rate
Halpha only
463-470 E8.2 Msun/pc2/yr e_SFR-Ha Uncertainty, rms, in SFR-Ha
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Note (1): To estimate IHα, we use the collection of literature Hα
maps compiled and processed by Leroy+ (2012AJ....144....3L 2012AJ....144....3L). These
draw heavily on LVL and SINGS (Kennicutt+ 2003PASP..115..928K 2003PASP..115..928K and
Lee+ 2009, J/ApJ/706/599). This estimate assumes a Kroupa initial mass
function (IMF). The correction to a Chabrier IMF is modest.
See Section 2.5.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 21Mar-2019