phasing alma for vlbi - max planck society · collaboration • alma phasing collaborators: nrao,...
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Phasing ALMA for VLBI
Sheperd Doeleman MIT Haystack Observatory
Collaboration• ALMA Phasing collaborators: NRAO, Haystack,
MPIfR, ASIAA, NAOJ, U. Concepcion• Other (sub)mm VLBI collaborators:
– JCMT– SAO/CfA, SMA– CSO– ARO/SMT– CARMA– UCBerkeley– IRAM
GR Model 7 Stations 13 Stations
April 2009: SgrA* Flare on Rsch scales
Fish et al, ApJL, v727, L36 2011
Text
On all three days, calibrator 1924-292 is stable, but SgrA* increases influx density on day 97, without a change in size (43uas).
VLBI Traction on Black Hole Orbits
Upper left: hot spot in accretion flow orbits BH at Innermost Stable Circular Orbit (ISCO). Upper right: triangle of stations - SMTO, ALMA, SMA. Lower left: closure phase as a function of time. Note that orbit period is ~30 min, so many orbits observed during a single night. Extraction of orbital period gives an estimate of BH spin.
Tracking Black Hole Orbits with VLBI
Spin = 0.9Hot-spot at ~ 6RgPeriod = 27 min.
Text
Shows time variable closure phases due toorbiting hot spot as number of phased ALMAantennas increases.
Tracking Black Hole Orbits with VLBI
Spin = 0.9Hot-spot at ~ 6RgPeriod = 27 min.
Text
Shows time variable closure phases due toorbiting hot spot as number of phased ALMAantennas increases.
Tracking Black Hole Orbits with VLBI
Spin = 0.9Hot-spot at ~ 6RgPeriod = 27 min.
Text
Shows time variable closure phases due toorbiting hot spot as number of phased ALMAantennas increases.
ALMA Vitals• 64 x 12m dishes: 96m effective dish.• Excellent site
– SEFD (1.3mm) ~ 100Jy– SEFD (3mm) ~ 70Jy– SEFD (7mm) ~ 40Jy
• VLBA-ALMA baselines x10 sensitivity of single VLBA-VLBA baseline at 3mm.
• N-S uv coverage to VLBA sites is roughly equivalent to VLBA_MK to VLBA_SC in length.
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Phasing Interface Card
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Phased Sum Data
VLBI Recorders
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Design for Real-time ALMA phasing
ALMA Phasing Timeline• Start 2011 (Fnding Proposal Submitted to NSF)• Development, Design, Software: 2011-2013• Integration, First light (1,3mm): 2013• Commissioning: 2014-2015• User Capability onwards.
• Implemented in parallel with normal ALMA construction: will not impact ALMA timeline.
9
7mm, 3mm VLBI with ALMA• M87: jet genesis, collimation• AGN: polarization, pan-chromatic studies• SiO maser astrometry:
– link IR-radio at Galactic Center– possible distance to LMC
• Gravitational Lenses: central images• High resolution molecular absorption:
– PKS 1830-211: isotopic abundances, evolution of fundamental constants
• LMT/GBT: parallax of SgrA* with VLBA (3mm) 10