J/A+A/659/A67 IRAM spectra of 4 Class I sources (Mercimek+, 2022)
Chemical survey of Class I protostars with the IRAM-30m.
Mercimek S., Codella C., Podio L., Bianchi E., Chahine L., Bouvier M.,
Lopez-Sepulcre A., Neri R., Ceccarelli C.
<Astron. Astrophys. 659, A67 (2022)>
=2022A&A...659A..67M 2022A&A...659A..67M (SIMBAD/NED BibCode)
ADC_Keywords: YSOs ; Spectra, radio
Keywords: astrochemistry - stars: formation - ISM: molecules -
Abstract:
Class I protostars are a bridge between Class 0 protostars (≤105yr
old), and Class II (≥106yr) protoplanetary disks. Recent studies
show gaps and rings in the dust distribution of disks younger than
1Myr, suggesting that planet formation may start already at the Class
I stage. To understand what chemistry planets will inherit, it is
crucial to characterize the chemistry of Class I sources and o
investigate how chemical complexity evolves from Class 0 protostars to
protoplanetary disks.
There are two goals: (i) to perform a census of the molecular
complexity in a sample of four Class I protostars, and (ii) to compare
the data with the chemical compositions of earlier and later phases of
the Sun-like star formation process.
We performed IRAM-30m observations at 1.3mm towards four Class I
objects (L1489-IRS, B5-IRS1, L1455-IRS1, and L1551-IRS5). The column
densities of the detected species were derived assuming local
thermodynamic equilibrium (LTE) or large velocity gradients (LVGs).
We detected 27 species: C-chains, N-bearing species, S-bearing
species, Si-bearing species, deuterated molecules, and interstellar
complex organic molecules (iCOMs; CH3OH, CH3CN, CH3CHO, and
HCOOCH3). Among the members of the observed sample, L1551-IRS5 is
the most chemically rich source. Different spectral profiles are
observed: (i) narrow lines (∼1km/s) towards all the sources, (ii)
broader lines (∼4km/s) towards L1551-IRS5, and (iii) line wings due to
outflows (in B5-IRS1, L1455-IRS1, and L1551-IRS5). Narrow c-C3H2
emission originates from the envelope with temperatures of 5-25K and
sizes of ∼2"-10". The iCOMs in L1551-IRS5 reveal the occurrence of hot
corino chemistry, with CH3OH and CH3CN lines originating from a
compact (∼0.15") and warm (T>50K) region. Finally, OCS and H2S seem
to probe the circumbinary disks in the L1455-IRS1 and L1551-IRS5
binary systems. The deuteration in terms of elemental D/H in the
molecular envelopes is: ∼10-70% (D2CO/H2CO), ∼5-15% (HDCS/H2CS),
and ∼1-23% (CH2DOH/CH3OH). For the L1551-IRS5 hot corino we derive
D/H∼2% (CH2DOH/CH3OH).
Carbon chain chemistry in extended envelopes is revealed towards all
the sources. In addition, B5-IRS1, L1455-IRS1, and L1551-IRS5 show a
low-excitation methanol line that is narrow and centered at systemic
velocity, suggesting an origin from an extended structure, plausibly
UV-illuminated. The abundance ratios of CH3CN, CH3CHO, and
HCOOCH3 with respect to CH3OH measured towards the L1551-IRS5 hot
corino are comparable to that estimated at earlier stages (prestellar
cores, Class 0 protostars), and to that found in comets. The
deuteration in our sample is also consistent with the values estimated
for sources at earlier stages. These findings support the inheritance
scenario from prestellar cores to the Class I phase when planets start
forming.
Description:
Observations were carried-out at the IRAM-30m telescope located on
Pico Veleta, Spain, during several sessions in July 2018 and May 2019.
Objects:
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RA (2000) DE Designation(s)
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04 04 43.1 +26 18 56.4 L1489-IRS = NAME LDN 1489 IRS
03 47 41.6 +32 51 43.5 B5-IRS1 = [BJE84] IRS 1
03 27 39.0 +30 12 59.3 L1455-IRS1 = NAME LDN 1455 IRS 1
04 31 34.1 +18 08 05.1 L1551-IRS5 = NAME L1551 IRS 5
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 97 4 The observed sample of Class I sources
sp/* . 4 Individual spectra
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Name Source name
12- 18 A7 --- Region Region
20- 21 I2 h RAh Right ascension (J2000) (1)
23- 24 I2 min RAm Right ascension (J2000)
26- 29 F4.1 s RAs Right ascension (J2000)
31 A1 --- DE- Declination sign (J2000) (1)
32- 33 I2 deg DEd Declination (J2000)
35- 36 I2 arcmin DEm Declination (J2000)
38- 41 F4.1 arcsec DEs Declination (J2000)
43- 45 I3 pc Dist Distance (2)
47- 50 F4.1 km/s Vsys Systemic velocity from present work
52- 55 F4.1 Lsun Lbol Bolometric luminosity of lower value of
bolometric luminostiy interval (3)
56 A1 --- --- [-]
57- 58 I2 Lsun BLbol ? Upper value of bolometric luminostiy interval
60- 77 A18 --- FileName Name of the spectrum file in subdirectory sp
79- 97 A19 --- SName Simbad name of the source
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Note (1): Coordinates: L1489-IRS from Jorgensen et al. (2009A&A...507..861J 2009A&A...507..861J),
B5-IRS1 and L1455-IRS1 from Hatchell et al. (2007A&A...468.1009H 2007A&A...468.1009H) and
Bergner et al. (2017ApJ...841..120B 2017ApJ...841..120B),
L1551-IRS5 from Froebrich (2005ApJS..156..169F 2005ApJS..156..169F).
Note (2): Distances from Zucker et al. (2019ApJ...879..125Z 2019ApJ...879..125Z)
Note (3): Bolometric lumonosities:
L1489-IRS from Green et al. (2013ApJ...770..123G 2013ApJ...770..123G),
B5-IRS1 from Evans et al. (2009ApJS..181..321E 2009ApJS..181..321E),
L1455-IRS1 from Dunham et al. (2013AJ....145...94D 2013AJ....145...94D),
L1551-IRS5 from Liseau et al. (2005ApJ...619..959L 2005ApJ...619..959L)
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Byte-by-byte Description of file: sp/*
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Bytes Format Units Label Explanations
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4- 13 F10.3 MHz Freq Observed frequency
19- 29 E11.5 K Tmb ?=-1000 Mean brightness temperature
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Acknowledgements:
Seuma Mercimek, seyma.mercimek(at)inaf.it
(End) Patricia Vannier [CDS] 03-Mar-2022