Fragmentaon 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 formaon Ophiuchus ‘Nessie’ – Jackson et al. 2010, Goodman et al. 2013 Stars to Life ‐ Gainesville 2013 2 Filaments and star cluster formaon Quesons: • how do filaments fragment & collapse? • how does gas flow along filaments to feed star formaon? Stars to Life ‐ Gainesville 2013 3 d ~ 260 pc Serpens South Cluster‐forming core: ‐ young: 77% Class I sources ‐1 ‐ acve: SFR ~ 90 Mo Myr W40 Gutermuth et al. 2008 Dense filaments 4 ‐ M ~ 10 Mo Global magnec field is 0.5 pc perpendicular to the main filament Sugitani et al. 2011 Filamentary accreon 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 idenficaon Dendrograms Rosolowsky et al. 2008 C++ code: Chris Beaumont (CfA) ‐ Idenfy hierarchical structures in PPV space ‐ Connect disnct emission peaks with parent structures Stars to Life ‐ Gainesville 2013 6 Stars to Life ‐ Gainesville 2013 7 Structure analysis Size – line width relaon 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 relaon with a single dense gas d = 4 w tracer (km/s) v 0.4 σ ‐ σv α R 0.1 Fragmentaon scales ‐ clump separaon 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 densies 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 separaons may be determined by thermal fragmentaon of filaments • HC7N emission highlights dense, chemically young, potenally infalling gas • Serendipitous discovery using large bandwidth available with GBT • Is HC7N abundant in other acve star forming regions? Stars to Life ‐ Gainesville 2013 14 the Aquila Ri Serpens Main AV = 18 Serpens NH3 W40 Serpens South 2MASS‐derived visual exncon over the Aquila ri Bontemps et al. 2010 Galacc Plane Stars to Life ‐ Gainesville 2013 15 Observaons ‐ ~ 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 resoluon ~ 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 opcally thin & thick spectra (Myers et al., PPIV) ‐ opcally thin spectra – no asymmetric infall line profile ‐ Δ σNT ~ 0.07 km/s between HC7N and NH3 due to radial infall? ‐ mass accreon rate ~ 5 Mo/Myr (isotropic – cylinder) Stars to Life ‐ Gainesville 2013 18 .