Fragmenta on and infall in the Serpens South cluster‐ forming region
Rachel Friesen
L. Medeiros (Berkeley), T. Bourke (CfA), J. Di Francesco (NRC‐HIA), R. Gutermuth (UMass) P. C. Myers (CfA), S. Schnee (NRAO) Arzoumanian et al. 2011 IC 5146 Filaments and star cluster forma on
Ophiuchus
‘Nessie’ – Jackson et al. 2010, Goodman et al. 2013
Stars to Life ‐ Gainesville 2013 2 Filaments and star cluster forma on
Ques ons:
• how do filaments fragment & collapse?
• how does gas flow along filaments to feed star forma on?
Stars to Life ‐ Gainesville 2013 3 d ~ 260 pc Serpens South Cluster‐forming core: ‐ young: 77% Class I sources ‐1 ‐ ac ve: SFR ~ 90 Mo Myr W40 Gutermuth et al. 2008
Dense filaments 4 ‐ M ~ 10 Mo
Global magne c field is 0.5 pc perpendicular to the main filament Sugitani et al. 2011
Filamentary accre on flow along southern filament
Stars to Life ‐ Gainesville 2013 Kirk et al. 20134 Data
NH3 (1,1), (2,2), (3,3)
32” (0.04 pc) FWHM
~20,000 spectra
Stars to Life ‐ Gainesville 2013 5 3D Structure iden fica on
Dendrograms
Rosolowsky et al. 2008
C++ code: Chris Beaumont (CfA)
‐ Iden fy hierarchical structures in PPV space ‐ Connect dis nct emission peaks with parent structures
Stars to Life ‐ Gainesville 2013 6 Stars to Life ‐ Gainesville 2013 7 Structure analysis
Size – line width rela on with a single dense gas
tracer (km/s) v
0.4 σ ‐ σv α R 0.1
0.01 0.1 Reff (pc)
Stars to Life ‐ Gainesville 2013 8 Structure analysis
Size – line width rela on with a single dense gas d = 4 w tracer (km/s) v
0.4 σ ‐ σv α R 0.1 Fragmenta on scales ‐ clump separa on Filament ‘width’ (pc) 0.01 0.1 ~ 4x filament diameter Sibling Distance (pc) e.g. Inutsuka & Miyama 1997
Stars to Life ‐ Gainesville 2013 9 HC7N J = 21‐20
Greyscale Herschel 500 μm dust emission
White contours
NH3 (1,1) mom 0
Red contours
HC7N mom 0 Stars to Life ‐ Gainesville 2013 10 HC7N in cold clouds ‐ Long carbon chains require gas‐phase C to form
‐ Abundance peak ~105 yr due to C locked into CO
‐ Gives rare mestamp for dense gas! C. Walsh et al. 2009 Abundance vs me for n = 104 cm‐3, T = 10 K Timescales shorter at higher densi es
Stars to Life ‐ Gainesville 2013 11 Radial infall? 1a, 1b clumps
Other HC7N regions Δ vLSR (km/s)
‐ Virial M/L
~ 50 Mo/pc ‐ Observed:
M/L ~ 130 Mo/pc
vLSRStars to Life ‐ Gainesville 2013 σNT Macc ~ 5 Mo /Myr12 Infall along filament
[NH ] / [HC N] 3 7 5 km/s/pc Primordial gas flow along K km/s filament?
Edge‐driven collapse mode in finite filaments? (e.g., Burkert & Hartmann 2004; Pon et al. 2012)
‐ Macc ~ 2‐3 Mo/Myr
Stars to Life ‐ Gainesville 2013 13 Summary
• Dendrograms reveal hierarchical structure in molecular line 3D data cubes
• Core separa ons may be determined by thermal fragmenta on of filaments
• HC7N emission highlights dense, chemically young, poten ally infalling gas
• Serendipitous discovery using large bandwidth available with GBT
• Is HC7N abundant in other ac ve star forming regions?
Stars to Life ‐ Gainesville 2013 14 the Aquila Ri
Serpens Main AV = 18
Serpens NH3
W40 Serpens South
2MASS‐derived visual ex nc on over the Aquila ri Bontemps et al. 2010 Galac c Plane
Stars to Life ‐ Gainesville 2013 15 Observa ons ‐ ~ 0.5o x 0.5o field mapped at 23.7 GHz (1 cm)
‐ NH3 (J,K) = (1,1), (2,2), (3,3) ‐ HC7N J = 21‐20 ‐ angular resolu on ~ 32” FWHM; pixel scale 13” ‐ ~ 20,000 spectra ‐ first shared‐risk science project with the 7‐beam KFPA K‐band Focal Plane Array
100 m Green Bank Telescope Stars to Life ‐ Gainesville 2013 16 Cold cloud chemistry Molecules remaining in gas phase
Stars to Life ‐ Gainesville 2013 17 Radial infall?
Infall line profiles for op cally thin & thick spectra (Myers et al., PPIV)
‐ op cally thin spectra – no asymmetric infall line profile
‐ Δ σNT ~ 0.07 km/s between HC7N and NH3 due to radial infall?
‐ mass accre on rate ~ 5 Mo/Myr (isotropic – cylinder)
Stars to Life ‐ Gainesville 2013 18