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Outflows, infall and evolution of a sample of embedded low-mass protostars. The William Herschel Line Legacy (WILL) survey | | J. C. Mottram
; E. F. van Dishoeck
; L. E. Kristensen
; A. Karska
; I. San José-García
; S. Khanna
; G. J. Herczeg
; Ph. Andr
; S. Bontemps
; S. Cabrit
; T.Carney
; N. Drozdovskaya
; M. Dunham
; J. Evans
; D. Fedele
; J. D. Green
; D. Harsono
; D. Johnstone
; J. K. Jørgensen
; V. Könyves
; B. Nisini
; M. V. Persson
; M. Tafalla
; R. Visser
; U. A. Yıldız
; | | Date: |
17 Jan 2017 | | Abstract: | [Abridged] We present spectroscopic observations in H$_{2}$O, CO and related
species with extit{Herschel} HIFI and PACS, as well as ground-based follow-up
with the JCMT and APEX in CO, HCO$^{+}$ and isotopologues, of a sample of 49
nearby ($d<$500,pc) candidate protostars. These data are used to study the
outflow and envelope properties of these sources. We also compile their
continuum SEDs in order to constrain their physical properties. Water emission
is dominated by shocks associated with the outflow, rather than the cooler,
slower entrained outflowing gas probed by ground-based CO observations. These
shocks become less energetic as sources evolve from Class 0 to Class I. The
fraction of mass in the outflow relative to the total envelope (i.e.
$M_{mathrm{out}}/M_{mathrm{env}}$) remains broadly constant between Class 0
and I. The median value ($sim$1$\%$) is consistent with a core to star
formation efficiency on the order of 50$\%$ and an outflow duty cycle on the
order of 5$\%$. Entrainment efficiency, as probed by
$F_{mathrm{CO}}/dot{M}_{mathrm{acc}}$, is also invariant with source
properties and evolutionary stage. The median value (6.3kms{}) suggests an
entrainment efficiency of between 30 and 60$\%$ if the wind is launched at
$sim$1AU. $L$[O,{sc i}] is strongly correlated with $L_{mathrm{bol}}$ but
not with $M_{mathrm{env}}$, while low-$J$ CO is more closely correlated with
the latter than the former. This suggests that [O,{sc i}] traces the
present-day accretion activity while CO traces time-averaged accretion over the
dynamical timescale of the outflow. $L$[O,{sc i}] does not vary from Class 0
to Class I, unlike CO and H$_{2}$O. This is likely due to the ratio of atomic
to molecular gas in the wind increasing as the source evolves, balancing out
the decrease in mass accretion rate. Infall signatures are detected in
HCO$^{+}$ and H$_{2}$O in a few sources. | | Source: | arXiv, 1701.4647 | | Services: | Forum | Review | PDF | Favorites | |
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