J/A+A/703/A277 Accretion luminosity of Class I protostars (Testi+, 2025)
The accretion luminosity of Class I protostars.
Testi L., Natta A., Gozzi S., Manara C.F., Williams J.P., Claes R.,
Lebreuilly U., Hennebelle P., Klessen R., Molinari S.
<Astron. Astrophys. 703, A277 (2025)>
=2025A&A...703A.277T 2025A&A...703A.277T (SIMBAD/NED BibCode)
ADC_Keywords: Protostars ; Spectra, millimetric/submm
Keywords: stars: formation - stars: pre-main sequence - stars: protostars -
stars: variables: T Tauri, Herbig Ae/Be
Abstract:
The value of the accretion luminosity during the early phases of star
formation is crucial information that aids in understanding how
stars form, but it is still very difficult to obtain.
We have developed a new methodology to measure accretion luminosity
using mid-infrared hydrogen recombination lines and applied it to a
limited sample of Class I protostars in the Taurus and Ophiuchus
star-forming regions.
We adopted the commonly used assumption that the properties of
disk-protostar accretion in Class I objects is similar to the
disk-star accretion in Class II objects. Using simultaneous
observations of three hydrogen recombination lines, Brγ,
Pfγ, and Brα, we derived the mean intrinsic line ratios,
and we verified that these are constant across the probed range of
photospheric and accretion properties. We established correlations
between the line luminosities and accretion luminosity.
We measured the extinction toward the line emission regions in Class I
protostars, comparing the observed line ratios to the Class II mean
values. We then derived the Class I accretion luminosities from the
established Class II correlations. We find that the accretion
luminosity dominates the bolometric luminosity for the more embedded
protostars, corresponding to lower values of the bolometric
temperature. As the bolometric temperature increases above ∼700K,
there is a sharp drop of the contribution of the accretion from the
bolometric luminosity.
Our findings are in qualitative agreement with numerical simulations
of star formation. We suggest our methodology be applied to larger and
more statistically significant samples of Class I objects to obtain a
more detailed comparison. Our results also suggest that by combining
multiple infrared line ratios, it will be possible to derive a more
detailed description of the dust extinction law in protostellar
envelopes.
Description:
The new spectra presented in this paper include eight Class II
objects, seven T Tauri stars (TTSs) and one Herbig Ae star (HAE), and
17 Class I and flat spectrum objects located in the Taurus and
ρ-Oph star-forming regions.
SpeX spectra of the Brgamma, Pfgamma, and Bralpha lines of class II
and class I YSOs.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 66 8 Class II SpeX data
table2.dat 107 24 Properties of the newly observed Class I/F and
those from Beck (2007AJ....133.1673B 2007AJ....133.1673B)
(for ID = 18 to 24)
list.dat 77 75 List of spectra
sp/* . 75 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- 23 A23 --- Name Name
25- 27 I3 pc Dist Distance are from Gaia EDR3
29- 32 F4.2 mag AK Extinction
33 A1 --- n_AK [bcd] Note on AK (1)
35- 39 F5.1 17W/m2 FBrgamma Brgamma flux
41- 43 F3.1 17W/m2 e_FBrgamma Brgamma flux error
45 A1 --- l_FPfgamma Limit flag on FPfgamma
46- 49 F4.1 17W/m2 FPfgamma Pfgamma flux
51- 53 F3.1 17W/m2 e_FPfgamma ? Pfgamma flux error
55 A1 --- l_FBralpha Limit flag on FBralpha
56- 60 F5.1 17W/m2 FBralpha Bralpha flux
62- 64 F3.1 17W/m2 e_FBralpha ? Bralpha flux error
66 A1 --- sp [*] * indicates spectra in subdirectory sp
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Note (1): Note as follows:
b = Extinction from Gangi et al. (2022A&A...667A.124G 2022A&A...667A.124G, cat. J/A+A/667/A124)
computed from AV using Cardelli et al. (1989ApJ...345..245C 1989ApJ...345..245C) with R=3.1
c = Extinction from Testi et al. (2022A&A...663A..98T 2022A&A...663A..98T, Cat. J/A+A/663/A98)
d = Extinction from Ubeira Gabellini et al. (2019MNRAS.486.4638U 2019MNRAS.486.4638U)
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- ID ID number
4- 26 A23 --- Name Name
28- 29 I2 h RAh Right ascension (J2000)
31- 32 I2 min RAm Right ascension (J2000)
34- 38 F5.2 s RAs Right ascension (J2000)
40 A1 --- DE- Declination sign (J2000)
41- 42 I2 deg DEd Declination (J2000)
44- 45 I2 arcmin DEm Declination (J2000)
47- 50 F4.1 arcsec DEs Declination (J2000)
52- 60 A9 --- Region Region
62- 66 F5.1 pc Dist Average cloud distance for Ophiuchus and
average distances of each sub-cloud for
Taurus (1)
68 A1 --- Class Class (2)
70- 72 F3.1 mag AKfg Foreground absorption in K band
74- 77 I4 K Tbol Bolometric temperature (3)
79- 82 I4 K E_Tbol Bolometric temperature error (upper value)
84- 87 I4 K e_Tbol Bolometric temperature error (lower value)
89- 92 F4.1 Lsun Lbol Bolometric luminosity (3)
94- 99 F6.1 Lsun E_Lbol Bolometric luminosity error (upper value)
102-105 F4.1 Lsun e_Lbol Bolometric luminosity error (lower value)
107 A1 --- sp [*] * indicates spectra in subdirectory sp
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Note (1): see Testi et al. (2022A&A...667A.124G 2022A&A...667A.124G, cat. J/A+A/667/A124);
Grasser et al. (2021A&A...652A...2G 2021A&A...652A...2G, Cat. J/A+A/652/A2);
Roccatagliata et al. (2020A&A...638A..85R 2020A&A...638A..85R, Cat. J/A+A/638/A85).
Note (2): The literature young stellar object classification is based on
Dunham et al. (2015ApJS..220...11D 2015ApJS..220...11D, Cat. J/ApJS/220/11),
Rebull et al. (2010ApJS..186..259R 2010ApJS..186..259R, Cat. J/ApJS/186/259), and
Beck (2007AJ....133.1673B 2007AJ....133.1673B).
Note (3): From this paper (see Sec. 4.3).
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 23 A23 --- Name Name
25- 41 A17 --- Line Spectrum title
43- 77 A35 --- FileName Name of the spectrum file in subdirectory sp
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Byte-by-byte Description of file: sp/*
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Bytes Format Units Label Explanations
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1- 18 F18.16 um lambda Wavelength
20- 39 F20.16 10-17W/m2/um Flux Flux
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Acknowledgements:
Leonardo Testi, leonardo.testi(at)unibo.it
(End) Patricia Vannier [CDS] 12-Nov-2025