Notes from Telecon 1

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Key Project Proposal Telecon 1, November 28th


  • Maryland: Shaye, Lee, Hao, Marc, Peter, Demerese
  • Illinois: Leslie, Dick, Manuel, Woojin
  • Caltech: Andrea
  • Arizona: Yancy
  • OVRO: Nikolaus
  • UBC: Erik
  • NRAO: John
  • Yale: Hector
  • JPL: Jens

---Start with some Science goals----

1. Testing Global Models of Star Formation:

  • Can't say anything directly about the magnetic fields
  • But can determine whether the observed kinematic structure better matches models with or without magnetic fields
  • It is a reasonable idea to coordinate with dust polarization projects if Dick is looking at sources in Perseus or Serpens

2. Optically thick in NGC 1333?

  • Lines in NGC 1333 are not horribly optically thick
  • Overall optical depths of several, but not such that hyperfine components are of comparable strength to the center line
  • Don't know this explicitly for HCO+ without isotopic observations. Perhaps Yancey can get us 12-m observations to estimate how optically thick we might be.

---Conversation opened up to discuss targets-----

3. John discusses OMC2/3

  • 50 Class 0/I protostars + more Class II sources in ~100 arcmin^2 field
  • Herschel maps exist and SCUBA2 will eventually exist
  • Ask if filament is consistent with magnetic quasi-static formation? or dynamic even is densest gas?
  • 5-6 arcsec resolution gets individual envelopes kinematics --- how connects with large scale cloud

---Lee discusses broad goals of Key----

4. Lasting value, data products of value to general community, regions others have worked on, good for complete data sets, data to justify ALMA followup.

---Continue discussing clouds----

5. Hector discusses Serpens

  • Serpens Main and Serpens South
  • Mapped by Stuart Corder for thesis with CARMA in 13CO and C18O
  • Serpens South getting attention because recently discovered
  • K band GBT data

---Do we want do probe clouds with different evolutionary stages?----

6. IRDCs?

  • Probably not any nearby, large IRDCs

7. California Cloud

  • Nearby
  • Talk to John B(?) with Charles Lada
  • Large section mapped 12CO and 13CO and followup with NIR
  • 12-m observed cores
  • A few degrees of cloud mapped by end of project

8. L1495

  • GBT proposal: 60 hour proposal to use KFPA to map 3 degree filament in NH3 (1-1) (2-2), CCS (?)
  • Hub of 1495: 20' x 20' region -- starless, class 0/I
  • Low density regions have magnetic field strength measured
  • Nearby

---Where in cloud do you choose to map??----

9. Not obvious what types of regions we go after

  • Do we go after clustered star formation?
  • Parts where not many stars have not formed yet?
  • Observe dense gas proceeding towards filament?

---Put things in perspective with time----

10. How much time can we justify?

  • Multi-semester Key Project
  • 400-500 hour level, not hurting ourselves
  • 1000 hour level is too big
  • 2-3 semesters at the least
  • This is one of areas for array to concentrate on overall several years so 150-200 hours per semester for 3 semester not crazy

---Discussion of alternatives to CARMA-23---

11. Why need CARMA-23 + SD?

  • CARMA-15 kills kinematics science due to negatives
  • Need good line profiles filled in with all spacings
  • But lose LSB :(

12. Does 3.5-m data make a huge difference?

  • 3.5-m doing important things in theory
  • The 3.5-3.5 and 3.5-6 baselines get important spacings
  • More effort has been put into pointing at 3.5-m at 3mm

13. "Time share" with 3.5-m?

  • Time share with 3.5-m uvcell distance?
  • Can't observe USB and LSB with 3.5-m since 3.5-m only USB.
  • No great alternatives found

---Go back to cloud approach---

14. Andrea suggests focusing on Perseus

  • Starless cores to class II sources
  • Variety of regions with different properties
  • Tons of complementary data: scuba, bolocam, ..,
  • Makes link to 1333 clear from point of view of evaluating proposal

15. Do 4 major subregions of Perseus?

  • Hurt us to be in same RA range, sucks up a lot of Orion time.
  • Scheduling array --- better to have two distinct RA spots.

16. Serpens or Oph?

  • Oph has signal-to-noise penalty
  • Serpense near equator so we get bad beam; straight lines in UV plane
  • Advantage, it is accessible to ALMA

---Consensus view: 2 clouds ! ---------------

17. Need large enough area to get context of surrounding material

  • trends in chemistry, not noticed across less than 1 pc.
  • still with ~10' scale

---Spectral Resolution?----

18. Advocate for 8 MHz mode with higher spectral resolution

  • Science goal of tracing infall motions with HCN(1-0) using hyperfine lines that are subsonic-- velocity resolution needs to be ~0.1-0.2 km/s

---Tracer Choice?----

19. C18O comparison to HCN and N2H+ is chemical measure of depletion

20. N2H+/C18O crude chemical evolution tracer

21. C18O is interesting near protostars; it is peaked at protostars due to liberation from grains; it is probe of the inner envelope

  • Is that worth doing 1/2 the number of clouds?

---General Proposal----

22. Probing wide variety and disparity of different star forming regions

23. What science can be done with few lines?

  • kinematics, large scale down to 1200 AU scale
  • trace morphology from parsec scale to 1200 AU scale
  • comparisons with stellar content
  • test models for how stars are forming
  • figure out how multiple tracers give you unique information
  • kinematics very different in regions --- no one core is alike, having kinematics of many
  • these 3 tracers probe dense gas between 10^4-6 -- nice range of densities traced here

24. Focus on Perseus and Serpens

  • Oph only up 4-5 hours tops at a time
  • 2-3 regions in each cloud

25. Who would like to help by choosing clouds?

  • Serpens: Hector, Manuel, John
  • Perseus: Andrea, Shaye, Jens, John

26. Need management plan

27. Next telecon Wednesday

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