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Imaging a galaxy-scale molecular outflow

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Imaging a galaxy-scale molecular outflow

ALMA has imaged expanding molecular shells in the starburst nucleus of NGC 253 at 50-parsec resolution. The extraplanar molecular gas closely tracks the Hα filaments, and connects to expanding molecular shells located in the starburst region. The molecular outflow rate is 9 Mo/yr, implying a ratio of mass-outflow rate to star-formation rate of about 3, indicating that the starburst-driven wind limits the star-formation activity and the final stellar content.These observations support the idea that the growth of large galaxies may be limited by strong wind-driven outflows.

Blue and magenta contours are CO emission at +/- 100 km/s around the nucleus of NGC 253 (Bollato ea. 2013)

AUI Executive Committee Meeting, September 3, 2013


Imaging of the CO Snow Line in a Solar Nebula Analog

ALMA has imaged the CO ‘snow line’ around TW Hya, an analog of the solar nebula.Planets form in the disks around young stars. Their formation efficiency and composition are intimately linked to the protoplanetary disk locations of "snow lines" of abundant volatiles. The chemical imaging used high spatial and spectral resolution observations of N2H+, a reactive ion present in large abundance only where CO is frozen out. The N2H+ emission is distributed in a large ring, with an inner radius that matches CO snow line model predictions. The extracted CO snow line radius of ~ 30 AU is a key parameter in constraining models of the formation dynamics of planetary systems.

ALMA and SMA images of dust, CO and N2H+ emission toward TW Hya. The red circle is the CO snow line prediction.

AUI Executive Committee Meeting, September 3, 2013

alma observation of the co snowline ring hd163296
ALMA Observation of the CO-Snowline RingHD163296
  • HD163296: 122 pc Ae star, 4Myr old, ~0.08Msun disk
  • Luminous: snowline distant from star. Massive: high column of gas
    • Qi et al (2011): Snowline at 155 AU; T~19K from 13CO SMA data
    • Mathews et al (2013): DCO+ with ALMA directly images snowline.
      • DCO+ limited by CO freezeout, T-dependent D enhancement

AUI Executive Committee Meeting, September 3, 2013

alma observations give new insights into protostars
ALMA Observations Give New Insights into Protostars

CO emission from the outflow in HH46/47 imaged by ALMA has revealed ultrafast gas, depositing energy and momentum into the nearby medium.

Arce, Mardones, Corder et al. 2013 ApJ 774, 39

  • In this ALMA image, blue colors show gas approaching us from HH46/47 and red shows receding gas.
  • The outflow shows both broad and collimated components; near the source velocities reach >30 km s-1
  • Discontinuities suggest episodic bursts on 100 yr timescales


AUI Executive Committee Meeting, September 3, 2013

alma images dust trap around distant star
ALMA Images ‘Dust Trap’ Around Distant Star
  • IRS 48 dust and gas observations.The inclined disk around IRS 48 as observed with ALMA 0.44mm observations, centered on the star (white star symbol).
    • A: ALMA observations, dashed ellipse shows a 63AU radius circle.
    • B: Integrated CO J=6-5 emission showing symmetric gas disk with Keplerian rotation (i=50o)
    • C: VLT VISIR image at 18.7μm
  • Proposed mechanism creates a dust trap in the disk of IRS 48:
    • A massive planet creates an annular gap in the gas disk.
    • A high-pressure vortex forms at the gap edge, collecting and trapping millimeter-sized dust particles that would otherwise spiral rapidly inward through the disk.

Van der Marel, van Dishoeck, Bruderer, et al. Science 340,1199

AUI Executive Committee Meeting, September 3, 2013

alma observes the coldest place in the universe the boomerang nebula
ALMA Observes the Coldest Place in the Universe: The Boomerang Nebula
  • Boomerang: a central hourglass-shaped Pre-Planetary nebula surrounded by a patchy, but roughly round, cold high-velocity outflow centered on a dense waist containing large grains
  • Adiabatic expansion has cooled the envelope substantially below the CMB temperature.
  • Outer regions of the CO flow are rewarmed, probably by photoelectric grain heating.

Sahai, Vlemmings, Huggins, et al. ApJ, in press.

AUI Executive Committee Meeting, September 3, 2013

alma opens a powerful new window into supernova ejecta
ALMA Opens a Powerful New Window into Supernova Ejecta
  • ALMA’s unprecedented sensitivity and resolution identify CO in the SN87A inner ejecta. SiO is also seen.
  • The C/O clumps in SN1987A contain at least 0. 01 M⊙ of 12 CO, an order of magnitude greater than measured in the first few years after the explosion: 12COhas continued to form over the past 25 years.
  • ALMA views the full velocity range of emission, unobscured by dust. Doppler tomography will be possible in CO and other molecules (SiO) to probe the spatial, chemicaland kinetic environment within the inner ejecta.

Kamenetzky, McCray, Indebetouw et al ApJ, in press

AUI Executive Committee Meeting, September 3, 2013