J/ApJ/849/1 Insights from synthetic star-forming regions. II. (Koepferl+, 2017)
Insights from synthetic star-forming regions.
II. Verifying dust surface density, dust temperature, and gas mass measurements
with modified blackbody fitting.
Koepferl C.M., Robitaille T.P., Dale J.E.
<Astrophys. J., 849, 1-1 (2017)>
=2017ApJ...849....1K 2017ApJ...849....1K (SIMBAD/NED BibCode)
ADC_Keywords: Star Forming Region; Models
Keywords: dust, extinction; hydrodynamics; infrared: diffuse background;
methods: observational; radiative transfer; stars: formation
Abstract:
We use a large data set of realistic synthetic observations (produced
in Paper I (2017ApJS..233....1K 2017ApJS..233....1K) of this series) to assess how
observational techniques affect the measurement physical properties of
star-forming regions. In this part of the series (Paper II), we
explore the reliability of the measured total gas mass, dust surface
density and dust temperature maps derived from modified blackbody
fitting of synthetic Herschel observations. We find from our
pixel-by-pixel analysis of the measured dust surface density and dust
temperature a worrisome error spread especially close to star
formation sites and low-density regions, where for those
"contaminated" pixels the surface densities can be under/overestimated
by up to three orders of magnitude. In light of this, we recommend to
treat the pixel-based results from this technique with caution in
regions with active star formation. In regions of high background
typical in the inner Galactic plane, we are not able to recover
reliable surface density maps of individual synthetic regions, since
low-mass regions are lost in the far-infrared background. When
measuring the total gas mass of regions in moderate background, we
find that modified blackbody fitting works well (absolute error: +9%;
-13%) up to 10kpc distance (errors increase with distance). Commonly,
the initial images are convolved to the largest common beam-size,
which smears contaminated pixels over large areas. The resulting
information loss makes this commonly used technique less verifiable as
now χ2 values cannot be used as a quality indicator of a fitted
pixel. Our control measurements of the total gas mass (without the
step of convolution to the largest common beam size) produce similar
results (absolute error: +20%; -7%) while having much lower median
errors especially for the high-mass stellar feedback phase.
Description:
To summarize Paper I (Koepferl+ 2017ApJS..233....1K 2017ApJS..233....1K), we used smoothed
particle hydrodynamics (SPH) simulations of a synthetic star-forming
region at several time-steps to produce synthetic observations. We
chose the SPH simulations of Dale & Bonnell (2011MNRAS.414..321D 2011MNRAS.414..321D) and
Dale+ (2012MNRAS.424..377D 2012MNRAS.424..377D ; 2013MNRAS.430..234D 2013MNRAS.430..234D ; 2013MNRAS.436.3430D 2013MNRAS.436.3430D ;
2014MNRAS.442..694D 2014MNRAS.442..694D), referred to as D14, because they include
high-mass stellar feedback, such as stellar ionization and winds, and
cover relatively large scales (run I: 104M☉ in mass, about
30pc in diameter). For more details about the SPH simulations used,
see Paper I or D14.
We extend (post-process) the SPH simulations with radiative transfer
calculations, which account for the stellar heating of the dust. We
used Hyperion (Robitaille T.P 2011A&A...536A..79R 2011A&A...536A..79R), a 3D dust
continuum Monte Carlo radiative transfer code.
We assumed a dust-to-gas ratio of dust/gas=0.01 and used Draine & Li
(2007ApJ...657..810D 2007ApJ...657..810D) dust grain properties for the radiative transfer
calculations.
For more information about the radiative transfer set-up of synthetic
star-forming regions and about the construction of the realistic
synthetic observations, see Paper I.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 208 828 Intrinsic and measured properties
for background B1
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See also:
J/A+A/591/A149 : Hi-GAL. inner Milky Way: +68≥l≥70 (Molinari+, 2016)
J/ApJ/849/2 : Insights from synthetic star-forming regions. III.
(Koepferl+, 2017)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I03 --- ID Running number (run)
5- 9 F5.3 Myr Time Time (time)
11- 21 A11 --- Sorter Sorter (sorter) (1)
23- 28 F6.1 Msun Mgas Gas mass (Mgas_sim)
30- 36 F7.1 Msun MgasB1 Gas mass without a realistic background (B1)
(Mgas_B1)
38- 44 F7.1 Msun MgasB1c MgasB1 χ2 corrected (MgasB1chi5)
46- 49 F4.2 --- R0 Median ratio of measured Σdustρ
to intrinsic Σdustρ (R0)
51- 54 F4.2 --- e_R0 R0 σMAD (Re0)
56- 59 F4.2 --- R1 Median ratio of measured Σdustρ
to intrinsic Σdustρ (R1)
61- 64 F4.2 --- e_R1 R1 σMAD (Re1)
66- 69 F4.2 --- R2 Median ratio of measured Σdustρ
to intrinsic Σdustρ (R2)
71- 74 F4.2 --- e_R2 R2 σMAD (Re2)
76- 80 F5.2 --- R3 Median ratio of measured Σdustρ
to intrinsic Σdustρ (R3)
82- 86 F5.2 --- e_R3 R3 σMAD (Re3)
88- 91 F4.2 --- R0c Median ratio of measured Σdustρ
to intrinsic Σdustρ;
χ2 corrected (R0c)
93- 96 F4.2 --- e_R0c R0c σMAD (Re0c)
98-101 F4.2 --- R1c Median ratio of measured Σdustρ
to intrinsic Σdustρ;
χ2 corrected (R1c)
103-106 F4.2 --- e_R1c R1c σMAD (Re1c)
108-111 F4.2 --- R2c Median ratio of measured Σdustρ
to intrinsic Σdustρ;
χ2 corrected (R2c)
113-116 F4.2 --- e_R2c R2c σMAD (Re2c)
118-122 F5.2 --- R3c Median ratio of measured Σdustρ
to intrinsic Σdustρ
χ2 corrected (R3c)
124-128 F5.2 --- e_R3c R3c σMAD (Re3c)
130-133 F4.2 --- T0 Median ratio of measured Tdust to
intrinsic dust (T0)
135-138 F4.2 --- e_T0 T0 σMAD (Te0)
140-143 F4.2 --- T1 Median ratio of measured Tdust to
intrinsic dust (T1)
145-148 F4.2 --- e_T1 T1 σMAD (Te1)
150-153 F4.2 --- T2 Median ratio of measured Tdust to
intrinsic dust (T2)
155-158 F4.2 --- e_T2 T2 σMAD (Te2)
160-163 F4.2 --- T3 Median ratio of measured Tdust to
intrinsic dust (T3)
165-168 F4.2 --- e_T3 T3 σMAD (Te3)
170-173 F4.2 --- T0c Median ratio of measured Tdust to
intrinsic dust; χ2 corrected (T0c)
175-178 F4.2 --- e_T0c T0c σMAD (Te0c)
180-183 F4.2 --- T1c Median ratio of measured Tdust to
intrinsic dust; χ2 corrected (T1c)
185-188 F4.2 --- e_T1c T1c σMAD (Te1c)
190-193 F4.2 --- T2c Median ratio of measured Tdust to
intrinsic dust; χ2 corrected (T2c)
195-198 F4.2 --- e_T2c T2c σMAD (Te2c)
200-203 F4.2 --- T3c Median ratio of measured Tdust to
intrinsic dust; χ2 corrected (T3c)
205-208 F4.2 --- e_T3c T3c σMAD (Te3c)
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Note (1): The different combinations of circumstellar set-ups
(CM1: no refinement, CM2: refinement with rotationally flattened
envelope, CM3: refinement with power-law envelope), orientations
(O1: xy plane, O2: xz plane, O3: yz plane), distances
(D1: 3kpc, D2: 10kpc) and resolution version (R2: scaled to pixel
size of SPIRE 500um, R3: convolved to beam size and scaled to pixel
size of SPIRE 500um).
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History:
From electronic version of the journal
References:
Koepferl et al. Paper I. 2017ApJS..233....1K 2017ApJS..233....1K
Koepferl et al. Paper II. 2017ApJ...849....1K 2017ApJ...849....1K This catalog
Koepferl et al. Paper III. 2017ApJ...849....2K 2017ApJ...849....2K Cat. J/ApJ/849/2
(End) Emmanuelle Perret [CDS] 12-Jun-2018