J/A+A/679/A112 California and Orion A clouds emission lines (Tafalla+, 2023)
Characterizing the line emission from molecular clouds.
II. A comparative study of California, Perseus, and Orion A.
Tafalla M., Usero A., Hacar A.
<Astron. Astrophys. 679, A112 (2023)>
=2023A&A...679A.112T 2023A&A...679A.112T (SIMBAD/NED BibCode)
ADC_Keywords: Molecular clouds ; Abundances ; Radio lines
Keywords: ISM: abundances - ISM: molecules -
ISM: individual objects: California -
ISM: individual objects: Perseus - ISM: individual objects: Orion A -
ISM: structure
Abstract:
We aim to characterize and compare the molecular-line emission of
three clouds whose star-formation rates span one order of magnitude:
California, Perseus, and Orion A.
We used stratified random sampling to select positions representing
the different column density regimes of each cloud and observed them
with the IRAM 30 m telescope. We covered the 3 mm wavelength band and
focused our analysis on CO, HCN, CS, HCO+, HNC, and N2H+.
We find that the line intensities depend most strongly on the H2
column density, with which they are tightly correlated. A secondary
effect, especially visible in Orion A, is a dependence of the line
intensities on the gas temperature. We explored a method that corrects
for temperature variations and show that, when it is applied, the
emission from the three clouds behaves very similarly. CO intensities
vary weakly with column density, while the intensity of traditional
dense-gas tracers such as HCN, CS, and HCO+ varies almost linearly
with column density. N2H+ differs from all other species in that
it traces only cold dense gas. The intensity of the rare HCN and CS
isotopologs reveals additional temperature-dependent abundance
variations. Overall, the clouds have similar chemical compositions
that, as the depth increases, are sequentially dominated by
photodissociation, gas-phase reactions, molecular freeze-out, and
stellar feedback in the densest parts of Orion A. Our observations
also allowed us to calculate line luminosities for each cloud, and a
comparison with literature values shows good agreement. We used our
HCN(1-0) data to explore the behavior of the HCN conversion factor,
finding that it is dominated by the emission from the outermost cloud
layers. It also depends strongly on the gas kinetic temperature.
Finally, we show that the HCN/CO ratio provides a gas volume density
estimate, and that its correlation with the column density resembles
that found in extragalactic observations.
Description:
The following two tables correspond to Tables B.1 and B.2 of the
paper. They contain the results from the stratified sampling
observations of the California cloud (80 positions) and Orion A cloud
(119 positions). Each table lists the coordinates of each observed
position, its estimated H2 column density, and the
velocity-integrated intensities for the brightest lines in the 3mm
wavelength band as observed with the IRAM-30m telescope. The first
digit in the source name indicates the column density bin to which it
belongs (10 denotes the highest column density bin). The line
intensities are in the main beam brightness temperature scale.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tableb1.dat 278 80 California cloud data
tableb2.dat 278 119 Orion A data
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See also:
J/A+A/642/A76 : California molecular cloud CO datacubes (Zhang+, 2020)
J/ApJ/921/23 : C18O dense cores identified in the CMC region (Guo+, 2021)
J/ApJS/217/7 : Orion A dense cores based on 1.1mm and C18O (Shimajiri+, 2015
J/ApJS/264/35 : C18O dense cores in Orion A molecular cloud (Takemura+, 2023
Byte-by-byte Description of file: tableb1.dat tableb2.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Name Source name (1)
12- 13 I2 h RAh Right ascension (J2000)
15- 16 I2 min RAm Right ascension (J2000)
18- 21 F4.1 s RAs Right ascension (J2000)
23 A1 --- DE- Declination sign (J2000)
24- 25 I2 deg DEd Declination (J2000)
27- 28 I2 arcmin DEm Declination (J2000)
30- 31 I2 arcsec DEs Declination (J2000)
34- 41 E8.2 cm-2 NH2 H2 column density
44- 50 E7.1 cm-2 e_NH2 H2 uncertainty column density uncertainty
53- 60 E8.2 K.km/s Int1 12CO(1-0) intensity
63- 69 E7.1 K.km/s e_Int1 12CO(1-0) intensity uncertainty
71- 79 E9.2 K.km/s Int2 13CO(1-0) intensity
82- 88 E7.1 K.km/s e_Int2 13CO(1-0) intensity uncertainty
90- 98 E9.2 K.km/s Int3 C18O(1-0) intensity
101-107 E7.1 K.km/s e_Int3 C18O(1-0) intensity uncertainty
109-117 E9.2 K.km/s Int4 HCN(1-0) intensity (1)
120-126 E7.1 K.km/s e_Int4 HCN(1-0) intensity uncertainty
128-136 E9.2 K.km/s Int5 CS(2-1) intensity
139-145 E7.1 K.km/s e_Int5 CS(2-1) intensity uncertainty
147-155 E9.2 K.km/s Int6 HNC(1-0) intensity
158-164 E7.1 K.km/s e_Int6 HNC(1-0) intensity uncertainty
166-174 E9.2 K.km/s Int7 HCO+(1-0) intensity
177-183 E7.1 K.km/s e_Int7 HCO+(1-0) intensity uncertainty
185-193 E9.2 K.km/s Int8 N2H+(1-0) intensity (2)
196-202 E7.1 K.km/s e_Int8 N2H++(1-0) intensity uncertainty
204-212 E9.2 K.km/s Int9 H13CN(1-0) intensity
215-221 E7.1 K.km/s e_Int9 H13CN(1-0) intensity uncertainty
223-231 E9.2 K.km/s Int10 C34S(2-1) intensity
234-240 E7.1 K.km/s e_Int10 C34S(2-1) intensity uncertainty
242-250 E9.2 K.km/s Int11 HN13C(1-0) intensity
253-259 E7.1 K.km/s e_Int11 HN13C(1-0) intensity uncertainty
261-269 E9.2 K.km/s Int12 H13CO+(1-0) intensity
272-278 E7.1 K.km/s e_Int12 H13CO+(1-0) intensity uncertainty
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Note (1): Source names are
CAL-NN_NN for California cloud, ORIA-NN_NN for Orina A cloud.
Note (2): For HCN(1-0) and N2H+(1-0), the intensity includes the contribution
from all detected hyperfine components.
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Acknowledgements:
Mario Tafalla, m.tafalla (at) oan.es
(End) Patricia Vannier [CDS] 18-Sep-2023