Atomic Gas associated with GMCs in the LMC

Atomic Gas associated with GMCs in the LMC Annie Hughes (MPIA), T. Wong (U. Illinois), J. Ott (NRAO), E. Muller (NAOJ), J. Pineda (JPL) & the MAGMA team

A Simple Question • Are GMCs dynamically decoupled from their environment? Bolatto et al. 2008 Yes? Pcl ~ 0. 47 αvir G Σ 2 for Σ ~ 100 M�/pc 2, Pcl/k. B ~ 105 K cm-3 vs. PISM/k. B ~ 2 x 104 K cm-3 (Cox 2005) ⇒ GMCs strongly self -gravitating

A Simple Question • Are GMCs* dynamically decoupled from their environment? No? In the LMC, • ΣH 2 ~ 30 M�/pc 2 & Rmol < 1 • Pext ~ Pkin, ISM + Pgrav, (HI+H 2) • Pcl, kin~ Pext ~ 2 x 104 K cm-3 * in the LMC For comparison to M 33& M 51, see poster #14 by Dario Colombo

The MAGellanic Mopra Assessment Background: Hα MCELS, Smith et al. 1999 MAGMA Observations ~ 3. 6 square degrees 114 NANTEN clouds ~80% of LMC’s CO flux θfwhm = 45” (11 pc) Δv = 0. 53 km/s Mopra Telescope

MAGMA Tmb [K] Background: Hα MCELS, Smith et al. 1999 LSR Velocity [km/s] Background: 24 um SAGE, Meixner et al. 2006

MAGMA Tmb [K] Background: Hα MCELS, Smith et al. 1999 LSR Velocity [km/s] Background: 24 um SAGE, Meixner et al. 2006

The MAGMA Survey First Public Data Release: http: //mmwave. astro. illinois. edu/magma/DR 1 LSR Velocity [km/s] Wong et al, 2011, Ap. Js, in press, ar. Xiv: 1108. 5715) Tmb [K] Background: Hα MCELS, Smith et al. 1999

“Top Down” GMC formation Predictions: i) Velocity gradients should align with Galactic rotation ii) Angular momentum conserved <<< Previous Observations: MW & M 33: Blitz 1990, 1993; Phillips 1999; Rosolowsky et al 2003; Koda et al 2006, Imara et al. 2011 a&b i) Gradients weakly aligned with Galactic rotation (or not at all) ii) Gradients are ~10 times smaller than model predictions M 33

Velocity Gradients of MAGMA GMCs Linear gradients provide a reasonable fit to velocity field for ~50% of resolved clouds in the MAGMA sample 143 clouds Red bar indicates ~100 pc

Spatial Organization of CO Gradients prograde Kim et al 2003 Some localised coherence, but GMCs show no strong preference for prograde rotation

A signature of cloud rotation? Gradients contributes a significant fraction of GMC linewidth But no correlation between gradient direction and GMC morphology

Gradients in atomic gas around GMCs Local HI gradient measured directly from observed HI map (not estimated from galactic rotation). Racc ~ region required to accumulate MGMC assuming ΣHI = 10, 20 M�/pc 2 Kim et al 2003 Tmb [K] HI Tb [K] 2 Racc LSR Velocity [km/s]

Comparison of CO & HI gradients

Summary • GMC gradients show no clear relationship to overall rotation of LMC disk. • Gradients are large relative to total GMC linewidths, but no correlation between gradient direction and cloud morphology • Gradients in CO and surrounding HI have similar magnitude • Gradients in CO & HI show some degree of alignment • Are Specific momentum of GMCs significantly less GMCsangular in the LMC dynamically decoupled from their environment? than prediction. No. from top-down formation model

Properties of LMC GMCs have: Size ~ 10 to 150 pc Mass ~ 103 to 106 M� Mass ~ 30 M�pc-2 For comparison to M 33& M 51, see poster #14 by Dario