An Ammonia Spectral Map of the L1495-B218 Filaments in the Taurus Molecular Cloud: II CCS & HC$_7$N Chemistry and Three Modes of Star Formation in the Filaments. (arXiv:1812.06121v1 [astro-ph.GA])

An Ammonia Spectral Map of the L1495-B218 Filaments in the Taurus Molecular Cloud: II CCS & HC$_7$N Chemistry and Three Modes of Star Formation in the Filaments. (arXiv:1812.06121v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Seo_Y/0/1/0/all/0/1">Young Min Seo</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Majumdar_L/0/1/0/all/0/1">Liton Majumdar</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Goldsmith_P/0/1/0/all/0/1">Paul F. Goldsmith</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Shirley_Y/0/1/0/all/0/1">Yancy L. Shirley</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Willacy_K/0/1/0/all/0/1">Karen Willacy</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ward_Thompson_D/0/1/0/all/0/1">Derek Ward-Thompson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Friesen_R/0/1/0/all/0/1">Rachel Friesen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Frayer_D/0/1/0/all/0/1">David Frayer</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Church_S/0/1/0/all/0/1">Sarah E. Church</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chung_D/0/1/0/all/0/1">Dongwoo Chung</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cleary_K/0/1/0/all/0/1">Kieran Cleary</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cunningham_N/0/1/0/all/0/1">Nichol Cunningham</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Devaraj_K/0/1/0/all/0/1">Kiruthika Devaraj</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Egan_D/0/1/0/all/0/1">Dennis Egan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gaier_T/0/1/0/all/0/1">Todd Gaier</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gawande_R/0/1/0/all/0/1">Rohit Gawande</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gundersen_J/0/1/0/all/0/1">Joshua O. Gundersen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Harris_A/0/1/0/all/0/1">Andrew I. Harris</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kangaslahti_P/0/1/0/all/0/1">Pekka Kangaslahti</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Readhead_A/0/1/0/all/0/1">Anthony C.S. Readhead</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Samoska_L/0/1/0/all/0/1">Lorene Samoska</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sieth_M/0/1/0/all/0/1">Matthew Sieth</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Stennes_M/0/1/0/all/0/1">Michael Stennes</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Voll_P/0/1/0/all/0/1">Patricia Voll</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+White_S/0/1/0/all/0/1">Steve White</a>

We present deep CCS and HC$_7$N observations of the L1495-B218 filaments in
the Taurus molecular cloud obtained using the K-band focal plane array on the
100m Green Bank Telescope. We observed the L1495-B218 filaments in CCS $J_N$ =
2$_1$$-$1$_0$ and HC$_7$N $J$ = 21$-$20 with a spectral resolution of 0.038 km
s$^{-1}$ and an angular resolution of 31$”$. We observed strong CCS emission
in both evolved and young regions and weak emission in two evolved regions.
HC$_7$N emission is observed only in L1495A-N and L1521D. We find that CCS and
HC$_7$N intensity peaks do not coincide with NH$_3$ or dust continuum intensity
peaks. We also find that the fractional abundance of CCS does not show a clear
correlation with the dynamical evolutionary stage of dense cores. Our findings
and chemical modeling indicate that the fractional abundances of CCS and
HC$_7$N are sensitive to the initial gas-phase C/O ratio, and they are good
tracers of young condensed gas only when the initial C/O is close to solar
value. Kinematic analysis using multiple lines including NH$_3$, HC$_7$N, CCS,
CO, HCN, & HCO$^+$ suggests that there may be three different star formation
modes in the L1495-B218 filaments. At the hub of the filaments, L1495A/B7N has
formed a stellar cluster with large-scale inward flows (fast mode), while
L1521D, a core embedded in a filament, is slowly contracting due to its
self-gravity (slow mode). There is also one isolated core that appears to be
marginally stable and may undergo quasi-static evolution (isolated mode).

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