1. 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.
The Starburst-Driven Molecular Wind in NGC 253 and the Suppression of Star Formation
Bollato et al Nature 499, 450
Blue and magenta contours are CO emission at +/- 100 km/s around the nucleus of NGC 253 (Bollato ea. 2013)
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2. 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.
Imaging of the CO Snow Line in a Solar Nebula Analog
Qi, C. et al. Science Express, July 18, 2013
ALMA and SMA images of dust, CO and N2H+ emission toward TW Hya. The red circle is the CO snow line prediction.
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3. ALMA Observation of the CO-Snowline Ring HD163296
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
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4. 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 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
ESO/ALMA (ESO/NAOJ/NRAO)/ H. Arce
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5. 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.
IRS 48 dust and gas observations.The inclined disk around IRS 48 as observed with ALMA Band 9 observations, centered on the star (white star symbol). The ALMA beam during the observations is 0.32′′ × 0.21′′ and is indicated with a white ellipse in the lower left corner. (A) The 0.44-mm (685 GHz) continuum emission expressed both in flux density and relative to the root mean square (rms) level (σ = 0.82 mJy per beam). The 63 AU radius is indicated by a dashed ellipse. (B) The integrated CO 6-5 emission over the highest velocities in contours (6,12,...,60σCO levels, σCO = 0.34 Jy km s−1): integrated over –3 to 0.8 km s−1 (blue) and 8.3 to 12 km s−1 (red), showing a symmetric gas disk with Keplerian rotation at an inclination i = 50°. The green background shows the 0.44-mm continuum. The position angle is indicated in the upper right corner. (C) The Very Large Telescope Imager and Spectrometer for the mid-infrared (VISIR) 18.7-μm emission in orange contours (36 to 120σVISIR levels in steps of 12σVISIR, σVISIR = 0.2 Jy arc sec−2) and orange colors, overlayed on the 0.44-mm continuum in green colors and the 5σ contour line in green. The VISIR beam size is 0.48′′ in diameter and is indicated with an orange circle in the bottom right corner.
Van der Marel, van Dishoeck, Bruderer, et al. Science 340,1199
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6. 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.
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7. 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 M⊙ of 12 CO, an order of magnitude greater than measured in the first few years after the explosion: 12CO has 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, chemical and kinetic environment within the inner ejecta.
Kamenetzky, McCray, Indebetouw et al ApJ, in press
Simple models show the lines are emitted from at least 0.01 M⊙ of CO at a
temperature > 14 K, confined within at most 35% of a spherical volume expanding at km s−1 .
Moreover, we locate the emission within 1′′ of the central debris.
Fig caption: color composite image of SN 1987A. The unresolved
12CO 2-1 line emission detected by ALMA is shown in red, and the
red ellipse in the corner is the synthesized beam. Also shown are
the H emission (blue) and [Si i]+[Fe ii] μm emission (green
in the ring; yellow in the ejecta) observed with the Hubble Space
Telescope (Larsson et al. 2013).
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