J/A+A/584/A93 Galactic cold cores. V. Dust opacity (Juvela+, 2015)
Galactic cold cores. V. Dust opacity.
Juvela M., Ristorcelli I., Marshall D., Montillaud J., Pelkonen V.-M.,
Ysard N., McGehee P., Paladini R., Pagani L., Malinen J.,
Rivera-Ingraham A., Lefevre C., Toth L.V., Montier L.A., Bernard J.-P.,
Martin P.
<Astron. Astrophys. 584, A93 (2015)>
=2015A&A...584A..93J 2015A&A...584A..93J (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Nebulae, dark ; Extinction
Keywords: ISM: clouds - infrared: ISM - submillimeter: ISM -
dust, extinction - stars: formation - stars: protostars
Abstract:
The project Galactic Cold Cores has carried out Herschel photometric
observations of interstellar clouds where Planck satellite survey has
located cold and compact clumps. The sources represent different
stages of cloud evolution from starless clumps to protostellar cores
and are located in different Galactic environments. We examine this
sample of 116 Herschel fields to estimate the submillimetre dust
opacity and to look for variations that could be attributed to the
evolutionary stage of the sources or to environmental factors,
including the location within the Galaxy. The submillimetre dust
opacity is derived from Herschel data and near-infrared observations
of the reddening of background stars are converted to near-infrared
optical depth. We investigate the systematic errors affecting these
parameters and use modelling to make corrections for the expected
biases. The ratio of 250µm and J band opacities is correlated with
the Galactic location and the star formation activity. Local
variations in the ratio τ(250µm)/τ(J) are searched using
the correlation plots and maps of the opacity ratio. We find a median
ratio of τ(250µm)/µ(J)=(1.6±0.2)*10-3, which is
more than three times the mean value reported for the diffuse medium.
Assuming an opacity spectral index β=1.8 instead of β=2.0,
the value would be smaller by ∼30%. No significant systematic
variation is detected with Galactocentric distance or with Galactic
height. Examination of the τ(250µm)/τ(J) maps reveals half
a dozen fields with clear indications of local increase of
submillimetre opacity, up to τ(250µm)/τ(J)∼4*10-3,
towards the densest clumps. These are all nearby fields with spatially
resolved clumps of high column density. We interpret the increase in
the far-infrared opacity as a sign of grain growth in the densest and
coldest regions of interstellar clouds.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 146 116 List of Herschel fields
tablee1.dat 107 116 Herschel observation IDs and reference regions
of extinction calculations
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See also:
VI/139 : Herschel Observation Log (Herschel Science Centre, 2013)
J/A+A/584/A92 : Galactic cold cores. IV. Cold submm sources (Montillaud+, 2015)
J/A+A/584/A94 : Galactic cold cores. VI. Herschel fields list (Juvela+, 2015)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 13 A13 --- Name Name of the field
15- 16 I2 h RAh Right ascension (J2000.0)
18- 19 I2 min RAm Right ascension (J2000.0)
21- 24 F4.1 s RAs Right ascension (J2000.0)
26 A1 --- DE- Declination sign (J2000.0)
27- 28 I2 deg DEd Declination (J2000.0)
30- 31 I2 arcmin DEm Declination (J2000.0)
33- 36 F4.1 arcsec DEs Declination (J2000.0)
38- 41 I4 arcmin2 Area Field size
43- 46 F4.2 pc Dist ? Estimated distance
48- 51 F4.2 pc E_Dist ? Error on Distance (upper value)
53- 56 F4.2 pc e_Dist ? Error on Distance (lower value)
58- 59 I2 h RARh Reference Right Ascension (J2000.0) (1)
61- 62 I2 min RARm Reference Right Ascension (J2000.0)
64- 67 F4.1 s RARs Reference Right Ascension (J2000.0)
69 A1 --- DER- Reference Declination sign (J2000.0) (1)
70- 71 I2 deg DERd Reference Declination (J2000.0)
73- 74 I2 arcmin DERm Reference Declination (J2000.0)
76- 79 F4.1 arcsec DERs Reference Declination (J2000.0)
81- 83 F3.1 arcmin Radius Radius of reference region
85-146 A62 --- Names ? Other names (2)
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Note (1): Coordinates of reference regions used for the
subtraction of local background emission.
Note (2): The names refer to the following catalogues:
Arch = Desert et al. (2008A&A...481..411D 2008A&A...481..411D, Cat. J/A+A/481/411)
B = Barnard (1919ApJ....49....1B 1919ApJ....49....1B) and Barnard et al.
(1927Barn..C......0B 1927Barn..C......0B), Cat. VII/220, <Barnard NNNA>
BDN = Bernes (1977A&AS...29...65B 1977A&AS...29...65B, <[B77] NNN>)
CB = Clemens & Barvainis (1988ApJS...68..257C 1988ApJS...68..257C, <[CB88] NNN>)
FeSr = Feitzinger & Stuewe (1984A&AS...58..365F 1984A&AS...58..365F, Cat. VII/68, <FeSt N-NNN>)
HMST = Hartley et al. (1986A&AS...63...27H 1986A&AS...63...27H, Cat. VII/191, )
LDN = Lynds (1962ApJS....7....1L 1962ApJS....7....1L, Cat. VII/7, )
MBM = Magnani et al. (1985ApJ...295..402M 1985ApJ...295..402M, )
MLB = Myers et al. (1983ApJ...264..517M 1983ApJ...264..517M, )
SLDN = Sandqvist & Lindroos (1976A&A....53..179S 1976A&A....53..179S, <Sandqvist NN>).
Most entries are looked up from Dutra & Bica (2002A&A...383..631D 2002A&A...383..631D,
Cat. J/A+A/383/631). Names starting with PCC and the entries S1-S10 refer
to names used in Juvela et al. (2010A&A...518L..93J 2010A&A...518L..93J)
and Planck Collaboration XXII (2011A&A...536A..12P 2011A&A...536A..12P).
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Byte-by-byte Description of file: tablee1.dat
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Bytes Format Units Label Explanations
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1- 13 A13 --- Name Name of Herschel field
15- 16 I2 h RAh Reference Right Ascension (J2000.0) (1)
18- 19 I2 min RAm Reference Right Ascension(J2000.0)
21- 24 F4.1 s RAs Reference Right Ascension(J2000.0)
26 A1 --- DE- Reference Declination (J2000.0) (1)
27- 28 I2 deg DEd Reference Declination(J2000.0)
30- 31 I2 arcmin DEm Reference Declination(J2000.0)
33- 36 F4.1 arcsec DEs Reference Declination(J2000.0)
38- 41 F4.1 arcmin Radius Radius of reference region
43- 52 I10 --- ID1 Herschel Observation ID (2)
54- 63 I10 --- ID2 ? Second Herschel Observation ID
65- 74 I10 --- ID3 ? Third Herschel Observation ID
76- 85 I10 --- ID4 ? Fourth Herschel Observation ID
87- 96 I10 --- ID5 ? Fifth Herschel Observation ID
98-107 I10 --- ID6 ? Sixth Herschel Observation ID
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Note (1): Reference regions used in extinction calculations of the
corresponding Herschel field.
Note (2): ID1-ID6 list Herschel observation IDs for all PACS and SPIRE
maps used.
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Acknowledgements:
Mika Juvela, mika.juvela(at)helsinki.fi
References:
Juvela et al., Paper I 2010A&A...518L..93J 2010A&A...518L..93J
Juvela et al., Paper II 2011A&A...527A.111J 2011A&A...527A.111J
Juvela et al., Paper III 2012A&A...541A..12J 2012A&A...541A..12J
(End) Mika Juvela [Univ. Helsinki, Finland], Patricia Vannier [CDS] 20-Jan-2015