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ISM_SPF_Astro-chem telecons

Page history last edited by pamela Klaassen 1 year, 7 months ago

 

 

Minutes from Telecons of the ISM, Star formation, Astrochemistry and Astrobiology Science Working Group. The table of contents below should link to the beginning of the minutes for each telecon (once this page is more populated)

 

 

 


 

Minutes of Telecon (30 July 2018)

 

Participants: Alvaro(AH), Claudia(CC), Jens(JK), Thushara(TP), Thomas(TS), Pamela(PK), Sarah(SS), Wayne(WH), Rene(RP), Henrik(HB), Emanuel(EC)

 

 

Wayne (on a MOS):

  • Chapman paper describing a sub-mm mos
  • made up of pick off arms
    • but diffraction spot is large at sub-mm
  • so, can we do this in a more compact way?
    • use new technologies in photonics & detectors on a chip
    • this could get us to a few hundred arms ‘patrolling’ a large FOV
  • more use for extra-galactic astronomy, but might find a use in galactic astronomy

 

 

Sarah (Polarisation):

  • Fill in niche in resolution and wavelengths
  • Need high resolution to bridge ALMA to Planck scales
    • res to ALMA, LAS to Planck
  • don’t need to worry about disks
  • from nearby to kpc distant clouds
  • suggestions that polarisation efficiency (fraction) change with wavelengths.
    • this allows a homogeneous study with a single telescope (consistency)
  • lines & Zeeman splitting
    • may not be appropriate for surveys, but snapshots would be incredible
  • ROVER used to be able to do full polarisation
    • left off due to poor uptake
    • would it be useful for AtLAST?
  • What exactly is the synergy with ALMA? 
    • followup or pathfinding.
  • if we make an efficient mapper, we can do both followup and pathfinding.
  • HB: we need to fold in what TolTEC can do
    • Sarah is on the science working group for TolTEC
      • they don’t know the mapping speed yet
    • line polarisation is unique though, TolTEC won’t do it.
  • SS: this would be a good probe of larger distance clouds (HMSFRs?)
    • but we’d have to get around the 90deg ambiguity
  • SS: TolTEC can’t do Zeeman
    • ALMA can only do this on small scales - therefore only known objects are in scope for ALMA
  • WH: worth talking to Jane Greaves
    • PI of ROVER, but calibration was an issue and so a better designed instrument would be better
  • JK: what science do we want to prioritise?
    • line polarisation is hard to do, and so might not be best suited for a ‘prime driver'
    • interesting science, but maybe not a prime driver
  • SS: agreed. this is tricky, and probably not the key science
  • HB: so, technically, why is it so difficult?  because for science, it could be amazing
  • SS: for X-POL, the receivers weren’t well aligned, so the stokes parameters were getting ‘blurred’, which is hard to correct for.
    • it’s supposed to being upgraded???
  • JK: it would be interesting if this went into the telescope design, rather than just the instrument design.  trickier to build, but easier to calibrate?
  • SS: line polarisation won’t have the same de-polarisation issues as dust, because the molecules aren’t changing 

 

 

 

Continuum & Line surveys of the plane [Thomas]:

  • We need to keep in mind what the telescope can and can’t do
    • not something that just improves what we have, but NEW things that we can’t really do now
  • Continuum surveys:
    • not trying to compete with hershel & spitzer, BGPS, ATLASGAL, etc, so what’s new?
    • increased sensitivity, resolution & freq coverage: what can we learn from that?
    • better mass sensitivity, but for filaments (etc), the ultimate limit becomes the confusion limit.
    • This might not be able to go much further than current surveys
  • Line surveys:
    • so far, line surveys have either been small in size, or small in wavelength coverage
    • the only one on the horizon is SEDIGISM (Shuller et al). it’s not very deep though
    • bigger telescope with massive receiver arrays would significantly help
    • but what science could we do with that kind of survey?
      • what are the scientific questions we could answer with that?
      • e.g. CI: this seems to be the science case for CCAT-prime
      • higher-freq = higher excitation lines
        • shocks & warm molecular material at cloud collisions
      • wide FOV (e.g. a few arcmin). ALMA fairly useless in that sense
  • HB: shouldn’t worry *too* much about CCAT-prime, since it’s so much smaller (more of a pathfinder)
  • TS: it’s more a question if whether the sensitivity and resolution are so important for CI
    • if it’s bright, we don’t need sensitivity. it’s the other lines that need sensitivity
  • RP: resolution is important, because we need the interface between the atomic to molecular 
  • JK: continuum mapping - multicolour camera could give temperatures automatically
  • HB: TolTEC is already 3 colours
  • JK: but their wavelengths aren’t as high as we’re looking to map
  • HB: worried that TolTEC takes a lot of the continuum case away
  • AH: multicolour dust is great, but what about multiple transitions of various species at the same time?
  • JK: how is that different than a wide band receiver?
  • AH: example of CO.
  • JK: could in principle design it so that the FOV could be surveyed by everything together at once.
  • TS: limitation is that continuum cameras read quickly, but heterodynes observing like that would create LOTS of data that way
  • JK: has been experimenting with the IRAM-30m

 

 

Claudia:

what are the big questions in Galactic astronomy? we seem to be data driven rather than science driven.

  • JK: there are so many that we can’t even list them
    • dense cores & filaments have only been studied nearby (<1 kpc)
      • what are their density structures?
    • column density PDF of clouds
    • Need high resolution and statistics to understand these questions well
  • HB: structure formation & kinematics from large to small.  how does the ISM evolve? conversion of the gas phases
    • transition from atomic to molecular is where the synergy with other telescopes comes in to play
  • CC: phase change & synergy with SKA are good cases 🙂
    CC: what about sofia?
  • HB: can’t really do large scales.

 

 

Circum-Galactic medium [Claudia]:

  • CGM: interface between ISM and IGM
    • metal rich gas up to 3R_virial from centre of galaxy
  • traces a lot of cold clumps
    • comes from MUSE observations at high redshift
  • so far, only examples are only at high-redshift
  • some attempts have been made for the galaxy (e.g. high-velocity clouds).
  • hard to probe CGM scales (eg 100 kpc) 

what we’re proposing for Galactic science is more constraining than what she’s proposing… but she needs longer integrations & therefore can’t be done with surveys

  • need stable baselines because their lines can be very broad
  • best bands for Claudia: 6,8, and 9
    • no need for VERY high frequency
  • FOV set by most nearby sources
  • resolution set by higher redshifted emission
    • e.g. is it resolved on 5 arcsec scales?
  • really the sensitivity is the limiting factor
    • WH: it’s more the mapping speed that we can improve on, but receivers themselves are about at the quantum limit

 

RP: what about array receivers?

  • CHAI: 64 pixel dual band. is that state of the art?
  • WH: that does seem to be the best right now.
    • not clear what’s limiting this:
      • LO?
  • TS: has been encouraged to think about arrays with hundreds of pixels, not tens of pixels 

 

 

 

 

 

Minutes of Telecon (16 July 2018)

 

Participants: Sarah (SS), Henrik (HB), Wayne (WH), Doug (DJ), and Claudia (CC), Jens (JK), Thomas (TS), Luigi (LS), Pamela (PK)Regrets: Nicola Schneider, Alessio Trafficante

 

Agenda:

  • Introductions (Name, Affiliation, area of expertise)
  • Discussion/Brainstorming of important science that only AtLAST could achieve
  • What do you see as the ideal sub-mm single dish of the (near) future (size, wavelength coverage, instrumentation)
  • Discussion of whether there should be a focus on ‘key science’ or distribution of science cases (or a combination)
  • Ways forward:
    • What does this group need in order to make progress on 
      • stating primary science objectives
      • determining technical feasibility of those objectives
  • Plan for followup telecons (incl. proposals for group leader/deputy to lead future discussion)
  • AOB

 

Minutes:

 

Brainstorming:Does the telescope need to be a survey instrument?

  • CI mapping of the milky way
  • niche: highest frequency end of ALMA
  • JK: wants higher site, smaller telescope
  • DJ: need to
    • get to high frequencies
    • observe continuum, lines (high spec. res) and polarisation
  • CC: survey instrument was what people were talking about, but there needs to be a lot of open PI time
  • HB: Agreed, but we also need the ability to do all encompassing (dedicated) surveys
  • DJ: then what kind of PI science would you envision?
  • CC: large area is key, but PI should be able to set depth
  • WH: but if ALMA gets FPAs, then its FOV increases significantly.
  • TS: even with FPAs, ALMA will still only see small areas, where as AtLAST would see degree scales.
  • WH: AtLAST could use a few hours to Kuiper Belt objects in a statistical view
  •  

The tradeoff between 50m or the high site (to 200 micron).

  • labour costs are much higher at the high-site
  • CCAT is going to try THz
  • going to the high-site will still give the ALMA bands, but it will lose some of its ties to ALMA
  • JK: need to work around what the LMT will be doing.
    • differentiating from LMT (DJ): 
      • higher-freq
      • wide field (LMT has 2.5 arcmin^2)
  • LS: we do need to work in mapping mode (when prompted by DJ on extra-galactic strategies). wants at least a MOS to get at 2mm spectrum
  • WH: suggested MOS (multi-object) for CCAT (more waveguides than pickoff arms)
  • Claudia: concerto on APEX. A Fabry-Perot IFU (link to astro-ph article
  • SS: Can we even get to 200 microns?  (DJ: ~15% of the time it should be possible, but it’s not clear whether it’s realistic or calibratable).
    • SS: this would probably be un-realistic for polarisation
    • DJ: agreed, this would be lines and continuum, not polarisation
    • HB: do we really need to go to 200 micron? (for polarisation)
    • DJ: interested in highest freq for the lines.. can probably only sell to 350 microns
    • HB: most of these high energy lines are from hot regions and therefore likely compact, and probably better for ALMA

high freq: what about the atomic lines. 809 CI line to be looked at with CCATHB: how extended is CO 6-5 & 7-6… do we just see the hot cores, or is it super extended?

  • should do some testing of that
  • nearby galaxies could be good for that test as well (higher surface brightness)
  • CC: find extended (10-15”) emission in CI, CO2-1, CS, etc but the problems are sensitivity and sensitivity to large scales.  pilot with APEX (30 hrs) CO 2-1, hasn’t seen anything yet.
    • CI in nearby galaxies on 10-15 kpc scales.
    • need for PI time to do these things

 

NOTE: US decadal survey details will be coming in the fall.

  • PK to ask at next WG leads meeting what the plan is for white papers 
    • 2 science papers (gal/extra gal), 2-3 tech (instruments, dish, site) papers. to be completed late 2018/early 2019.
    • Unclear where they will be submitted (impression that posting to astro-ph wasn’t enough)

 

Suggestion to have sub-groups looking at different science topics. ‘lead’ (initials in brackets) to lead discussions. If interested in contributing, please contact the ‘lead’ directly.Sub-working groups:

  • Polarisation (SS)  PK to contact Laura Fissel & Juan Soler as well
  • transients/monitoring (DJ)
  • spectral line galactic plane survey ??
  • Circum-galactic medium (CC) & Local galaxies
  • general continuum emission (JK)
  • Any others?

 

Action items:

  • WH: multiarm spectrometer specs for DJ
  • PK to report back on WG leads telecon (w.r.t white papers)

 

 

next telecon June 30, 4pm BST

 

 

 

 

 

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