J/ApJ/915/92 SOFIA CII and NII obs. of M101 and NGC6946 (Tarantino+, 2021)
Characterizing the multiphase origin of [CII] emission in M101 and NGC 6946
with velocity-resolved spectroscopy.
Tarantino E., Bolatto A.D., Herrera-Camus R., Harris A.I., Wolfire M.,
Buchbender C., Croxall K.V., Dale D.A., Groves B., Levy R.C., Riquelme D.,
Smith J.-DT., Stutzki J.
<Astrophys. J., 915, 92 (2021)>
=2021ApJ...915...92T 2021ApJ...915...92T
ADC_Keywords: Galaxies, IR; Interstellar medium; Molecular data; Abundances
Keywords: Photodissociation regions ; Interstellar medium ;
Cold neutral medium ; Molecular gas ; Far infrared astronomy ;
Spiral galaxies
Abstract:
The [CII] fine-structure transition at 158µm is frequently the
brightest far-infrared line in galaxies. Due to its low ionization
potential, C+ can trace the ionized, atomic, and molecular phases of
the ISM. We present velocity-resolved [CII] and [NII] pointed
observations from SOFIA/GREAT on ∼500pc scales in the nearby galaxies
M101 and NGC 6946 and investigate the multiphase origin of [CII]
emission over a range of environments. We show that ionized gas makes
a negligible contribution to the [CII] emission in these positions
using [NII] observations. We spectrally decompose the [CII] emission
into components associated with the molecular and atomic phases using
existing CO (2-1) and HI data and show that a peak signal-to-noise
ratio of 10-15 is necessary for a reliable decomposition. In general,
we find that in our pointings ≳50% of the [CII] emission arises from
the atomic phase, with no strong dependence on star formation rate,
metallicity, or galactocentric radius. We do find a difference between
pointings in these two galaxies, where locations in NGC 6946 tend to
have larger fractions of [CII] emission associated with the molecular
phase than in M101. We also find a weak but consistent trend for
fainter [CII] emission to exhibit a larger contribution from the
atomic medium. We compute the thermal pressure of the cold neutral
medium through the [CII] cooling function and find
log(Pth/k)=3.8-4.6[K/cm3], a value slightly higher than similar
determinations, likely because our observations are biased toward
star-forming regions.
Description:
Observations of M101 and NGC 6946 were taken using the German REceiver
for Astronomy at Terahertz Frequencies (GREAT; and its improved
successor upGREAT) on board the Stratospheric Observatory for Infrared
Astronomy (SOFIA) in cycles 2 and 4.
The cycle 2 (PI: Herrera-Camus; project 02_0098) data used the
original GREAT instrument. Observations were taken 2014 May 20 and 21,
with receivers tuned to 1900.5GHz ([CII]158um) and 1461.1GHz
([NII]205um). We adopt a uniform beam size of 15" for [CII] and 18"
for [NII].
The cycle 4 data (PI: Bolatto; project 04_0151) comprised 11 total
regions, five in M101 and six in NGC 6946, using the dual-polarization
upGREAT instrument on SOFIA. The observations of M101 were taken
during the upGREAT commissioning on 2015 December 9 and 10, and the
NGC 6946 observations were taken on 2016 May 12, 18, 19, and 25.
See Section 2 for further details.
Objects:
----------------------------------------------------------
RA (ICRS) DE Designation(s)
----------------------------------------------------------
14 03 12.58 +54 20 55.5 M101 = NAME Pinwheel
20 34 52.33 +60 09 13.2 NGC 6946 = LEDA 65001
----------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 71 80 [CII] SOFIA/GREAT spectra summary
table2.dat 44 27 [CII] Gaussian fits summary
table3.dat 81 18 Results of the decomposition
table4.dat 73 3 Single spectrum decomposition
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See also:
J/A+A/432/369 : Leiden Atomic and Molecular Database (LAMDA) (Schoeier+, 2005)
J/ApJS/178/247 : Hα and [NII] survey in local 11 Mpc (Kennicutt+, 2008)
J/A+A/486/629 : Effective collision strengths for C II (Tayal, 2008)
J/AJ/136/2563 : HI Nearby Galaxy Survey, THINGS (Walter+, 2008)
J/ApJ/703/1672 : Far-IR and Hα fluxes in galaxies (Kennicutt+, 2009)
J/ApJ/703/1569 : Radial distribution in SINGS gal. I. (Munoz-Mateos+, 2009)
J/ApJ/734/65 : CI radial velocities with HST/STIS (Jenkins+, 2011)
J/A+A/539/A143 : Nearby B-stars stellar param. and abundances (Nieva+, 2012)
J/ApJ/774/73 : ALMA CO observations of 30 Dor (Indebetouw+, 2013)
J/A+A/578/A53 : Spectroscopy of Herschel Dwarf Galaxy Survey (Cormier+, 2015)
J/A+A/575/A9 : M17-SW datacubes in C and CO lines (Perez-Beaupuits+, 2015)
J/A+A/586/A37 : M33 center and BCLMP302 [CII] spectroscopy (Mookerjea+, 2016)
J/A+A/589/A28 : N66, N88 & N25+N26 emission line maps (Requena-Torres+, 2016)
J/A+A/595/A34 : SOFIA Horsehead nebula region datacube (Risacher+, 2016)
J/A+A/591/A33 : [CII]158um and [NII]205um IC 342 spectra (Roellig+, 2016)
J/ApJ/845/96 : [CII] emission in the ISM of 20 nearby gal. (Croxall+, 2017)
J/A+A/599/A9 : NGC 4214 [CII] line profile (Fahrion+, 2017)
J/A+A/626/A23 : Herschel Dwarf Galaxy Survey PACS sp. (Cormier+, 2019)
J/A+A/632/A106 : LMC-N11 (LHA 120-N11) [CII], HI, CO sp. (Lebouteiller+, 2019)
J/A+A/621/A62 : 4 LMC SFRs velocity profile maps (Okada+, 2019)
J/A+A/643/A141 : Tracing total molecular gas in galaxies (Madden+, 2020)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 A7 --- Gal Galaxy
9- 12 A4 --- Reg Region, in Galaxy (G1)
14- 14 I1 --- Cycle [2/4] Cycle
16- 17 I2 h RAh [14/20] Hour of Right Ascension (J2000)
19- 20 I2 min RAm Minute of Right Ascension (J2000)
22- 25 F4.1 s RAs Second of Right Ascension (J2000)
27 A1 --- DE- [+] Sign of Declination (J2000)
28- 29 I2 deg DEd [54/60] Degree of Declination (J2000)
31- 32 I2 arcmin DEm Arcminute of Declination (J2000)
34- 37 F4.1 arcsec DEs Arcsecond of Declination (J2000)
39- 43 F5.3 --- Z [7.9/8.7] Metal abundance, 12+log(O/H)
45- 54 E10.3 Msun/yr/kpc2 SFRD [-1.4e-5/0.7] Star formation rate density
56- 61 F6.3 K.km/s I[CII] [-5.7/34.2] Integrated intensity,
[CII] (1)
63- 66 F4.2 K.km/s e_I[CII] [0.4/4.6] Uncertainty in I[CII]
68- 71 F4.2 K RMS [0.02/0.2] RMS
--------------------------------------------------------------------------------
Note (1): Divide by 1.43x105 to convert I[CII] from K.km.s-1 to
erg/s/cm2/sr (Goldsmith+ 2012ApJS..203...13G 2012ApJS..203...13G)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 A7 --- Gal Galaxy
9- 12 A4 --- Reg Region, in Galaxy (G1)
14- 17 F4.2 K Amp [0.06/1.2] Gaussian amplitude fit
19- 22 F4.2 K e_Amp [0.02/0.09] Uncertainty in Amp
24- 28 F5.1 km/s vpeak [-54.4/322] Fitted peak velocity
30- 33 F4.2 km/s e_vpeak [0.5/6.2] Uncertainty in vpeak
35- 38 F4.1 km/s FWHM [9/51] Full width half maximum of the Gaussian fit
40- 44 F5.2 km/s e_FWHM [1/15] Uncertainty in FWHM
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 A11 --- Property Property
13- 19 A7 --- Sample Sub-sample region selection (1)
21- 22 I2 --- Nsp [10/78] Number of spectra stacked
24- 28 F5.2 --- SNR-CII [10/24] Signal-to-noise, [CII]
30- 34 F5.2 10-2Msun/yr/kpc2 SFRD [0.7/20.1] Average weighted star
formation rate density
36- 39 F4.2 --- Z [8.4/8.62] Metal abundance,
12+log(O/H)
41- 44 F4.2 --- gc [0.2/0.7] Normalized galactocentric
radius, R/R25
46- 50 F5.2 Msun/pc2 Sgas [23.6/58.4] Total gas surface
density
52- 56 F5.2 --- fCO [-0.03/0.7] Fraction of the
integrated [CII] intensity
associated with molecular gas
58- 61 F4.2 --- e_fCO [0.07/0.23] Uncertainty in fCO
63- 66 F4.2 --- fHI [0.26/1.03] Fraction of the
integrated [CII] intensity
associated with atomic gas
68- 71 F4.2 --- e_fHI [0.07/0.26] Uncertainty in fHI
73- 76 F4.2 --- chi2-2c [0.32/3.29] Reduced χ2 using
both HI and CO
78- 81 F4.2 --- chi2-1c [0.64/3.27] Reduced χ2 using
CO or HI one-component model
--------------------------------------------------------------------------------
Note (1): Sub-samples as follows:
3sigma = regions with integrated [CII] intensities three times greater
than the RMS noise;
No Cuts = contain all of the spectra in the data.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 A7 --- Gal Galaxy
9- 12 A4 --- Reg Region, in Galaxy (G1)
14- 14 I1 --- Cycle [2/4] Cycle
16- 20 F5.2 --- SNR-CII [9/15] Signal-to-noise, [CII]
22- 26 F5.2 10-2Msun/yr/kpc2 SFRD [4.8/69] Average weighted star
formation rate density
28- 31 F4.2 --- Z [8.4/8.5] Metal abundance,
12+log(O/H)
33- 36 F4.2 --- gc [0.3/0.9] Normalized galactocentric
radius, R/R25
38- 43 F6.2 Msun/pc2 Sgas [44/132] Total gas surface density
45- 48 F4.2 --- fCO [0.39/0.53] Fraction of the
integrated [CII] intensity
associated with molecular gas
50- 53 F4.2 --- e_fCO [0.1/0.15] Uncertainty in fCO
55- 58 F4.2 --- fHI [0.46/0.65] Fraction of the
integrated [CII] intensity
associated with atomic gas
60- 63 F4.2 --- e_fHI [0.08/0.14] Uncertainty in fHI
65- 68 F4.2 --- chi2-2c [0.69/1.61] Reduced χ2 using
both HI and CO
70- 73 F4.2 --- chi2-1c [1.12/2.51] Reduced χ2 using
CO or HI one-component model
--------------------------------------------------------------------------------
Global notes:
Note (G1): Cycle 4 pointings are referred to by their region name and a number
denoting the pointing number in the array (e.g., N2-0 would be the
cycle 4 NGC 6946 region N2 and the 0th, central pointing).
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 16-Dec-2022