2009A&A...493...89E


Query : 2009A&A...493...89E

2009A&A...493...89E - Astronomy and Astrophysics, volume 493, 89-105 (2009/1-1)

The N2D+/N2H+ ratio as an evolutionary tracer of Class 0 protostars.

EMPRECHTINGER M., CASELLI P., VOLGENAU N.H., STUTZKI J. and WIEDNER M.C.

Abstract (from CDS):

Deuterated ions, especially H2D+ and N2D+, are abundant in cold (∼10 K), dense (∼105cm–3) regions, in which CO is frozen out onto dust grains. In such environments, the N2D+/N2H+ ratio can exceed the elemental abundance ratio of D/H by a factor of ≃104. We use deuterium fractionation to investigate the evolutionary state of Class 0 protostars. In particular, we expect the N2D+/N2H+ ratio to decrease as temperature (a sign of the evolution of the protostar) increases. We observed N2H+ 1-0, N2D+ 1-0, 2-1 and 3-2, C18O 1-0 and HCO+ 3-2 in a sample of 20 Class 0 and borderline Class 0/I protostars. We determined the deuteration fraction and searched for correlations between the N2D+/N2H+ ratio and well-established evolutionary tracers, such as TDust and the CO depletion factor. In addition, we compared the observational result with a chemical model. In our protostellar sample, the N2H+ 1-0 optical depths are significantly lower than those found in prestellar cores, but the N2H+ column densities are comparable, which can be explained by the higher temperature and larger line width in protostellar cores. The deuterium fractionation of N2H+ in protostellar cores is also similar to that in prestellar cores. We found a clear correlation between the N2D+/N2H+ ratio and evolutionary tracers. As expected, the coolest, i.e. the youngest, objects show the largest deuterium fractionation. Furthermore, we find that sources with a high N2D+/N2H+ ratio show clear indications of infall (e.g. δv<0). With decreasing deuterium fraction, the infall signature disappears and δv tends to be positive for the most evolved objects. The deuterium fractionation of other molecules deviates clearly from that of N2H+. The DCO+/HCO+ ratio stays low at all evolutionary stages, whereas the NH2D/NH3 ratio is >0.15 even in the most evolved objects. The N2D+/N2H+ ratio is known to trace the evolution of prestellar cores. We show that this ratio can be used to trace core evolution even after star formation. Protostars with an N2D+/N2H+ ratio above 0.15 are in a stage shortly after the beginning of collapse. Later on, deuterium fractionation decreases until it reaches a value of ∼0.03 at the Class 0/I borderline.

Abstract Copyright:

Journal keyword(s): ISM: clouds - ISM: evolution - ISM: molecules - stars: formation

Simbad objects: 40

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Number of rows : 40
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
#notes
1 LDN 1448 DNe 03 22.5 +30 35           ~ 501 0
2 IRAS 03222+3034 Y*O 03 25 22.32 +30 45 13.9           ~ 139 0
3 SSTc2d J032536.4+304522 Y*O 03 25 36.49 +30 45 22.2           ~ 193 1
4 IRAS 03225+3034 IR 03 25 36.49 +30 45 22.2           ~ 158 1
5 LDN 1448NA smm 03 25 36.49 +30 45 22.2           ~ 180 1
6 [SDA2014] West4 Y*O 03 25 38.83 +30 44 06.2           ~ 250 1
7 IRAS F03226+3033 Y*O 03 25 38.83 +30 44 06.2           ~ 325 0
8 NAME LDN 1455 IRS 1 cor 03 27 39.08 +30 13 03.1           ~ 151 0
9 [JBK93] A1 PoC 03 27 42.2 +30 12 43           ~ 3 0
10 [JBK93] A2 PoC 03 27 49.9 +30 11 43           ~ 3 0
11 LDN 1455 DNe 03 28 00.6480 +30 07 58.800           ~ 180 1
12 SSTYSV J032917.11+312745.5 cor 03 29 17.17 +31 27 46.5           ~ 39 0
13 [LMG94] Per 4 PoC 03 29 18.0 +31 27 31           ~ 10 0
14 SSTc2d J032923.5+313330 Y*O 03 29 23.47 +31 33 29.5           ~ 38 1
15 IRAS 03267+3128 cor 03 29 51.82 +31 39 06.0           ~ 51 0
16 [LMG94] Per 6 PoC 03 30 14.9 +30 22 48           ~ 13 0
17 IRAS 03271+3013 cor 03 30 15.159 +30 23 49.38           ~ 63 0
18 IRAS 03282+3035 cor 03 31 20.98 +30 45 30.1           ~ 167 0
19 2MASS J03331667+3107548 Y*O 03 33 16.68 +31 07 54.9           ~ 112 2
20 NAME Perseus Cloud SFR 03 35.0 +31 13           ~ 1238 0
21 NAME Per Region reg 03 37 00.0 +31 15 00           ~ 256 0
22 HH 211 cor 03 43 56.52 +32 00 52.8           ~ 332 0
23 IRAS 03407+3152 Y*O 03 43 59.64864 +32 01 53.9832           M0 32 1
24 IRAS 03445+3242 Y*O 03 47 41.603 +32 51 43.79           ~ 188 0
25 LDN 1527 DNe 04 39 53 +25 45.0           ~ 575 0
26 IRAS 04368+2557 Y*O 04 39 53.97816 +26 03 09.6804           ~ 259 0
27 LDN 1544 DNe 05 04 16.6 +25 10 48           ~ 793 0
28 NAME [BM89] L1544 cor 05 04 22.5 +25 11 36           ~ 435 1
29 NAME Ophiuchus Molecular Cloud SFR 16 28 06 -24 32.5           ~ 3396 1
30 NAME LDN 483 FIR Y*O 18 17 29.8 -04 39 38           ~ 65 0
31 LDN 483 DNe 18 17 35 -04 39.8           ~ 270 0
32 V* V371 Ser Or* 18 29 51.21240 +01 16 39.4860           ~ 106 1
33 [S2009] L723 XMM 8 * 19 17 53.1327617040 +19 12 16.426495764           ~ 38 0
34 LDN 723 DNe 19 18 12 +19 13.6           ~ 154 0
35 LDN 673A DNe 19 20 25.8 +11 19 52           ~ 8 0
36 IRAS 19180+1114 IR 19 20 25.8 +11 19 52           ~ 12 0
37 LDN 663 DNe 19 36 55 +07 34.4           ~ 607 0
38 IRAS 19345+0727 FIR 19 37 01.03 +07 34 10.9           ~ 66 0
39 NAME LDN 1157-mm Y*O 20 39 06.2 +68 02 15           ~ 178 0
40 LDN 1157 DNe 20 39 06.4 +68 02 13           ~ 545 0

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2022.09.27-12:47:19

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