ESAC report

Rebaselining Time Allocation procedure Other items

ARC, EU-FP6: see T. Wilson

I. ALMA Rebaseling

Most of the ESAC and ASAC discussions over the last year focussed on the ALMA rebaselining; see ASAC reports October 2004, March 2005 and October 2005

At each of their face-to-face meetings, the ASAC/ESAC was presented with various options for re-scoping of the project. The latest set of Baseline Change Proposals (BCPs) by the JAO was received on September 8.

ESAC/ASAC reaction to BCPs ESAC and ASAC discussed all science-related BCPs; obtained

clarifications from project where needed ESAC grouped BCPs in 4 categories, with increasing severity of

impact on science RE, PR, MA, U(nacceptable) ASAC decided on 3 categories, where MA implies Unacceptable

Terminology ‘defer’ unclear ESAC assumed that ‘defer’ implies that the BCP may be realized in the

first ~3-4 yr after completion of full array, either through development funding in operations budget or additional money

Because of strict US-NSF rules which prevent moving scope from construction to operations, it is more likely that defer implies an indefinite delay. ASAC has therefore moved several of these BCPs into MA category.

BCP discussion

1. 50 antennas: MA N=50 antennas is a reduction compared with 50

operational antennas, as recommend by ASAC in March 2005 report 50 antennas endorsed by STC

ALMA science driven by sensitivity and image quality Sensitivity ~ N => integration time ~N2

Factor 1.5 in time for N=50, 2.3 for N=40 compared with N=60

Image quality ~N(N-1) ~N2, or even N3 as stressed in Blandford committee report

Milky Way galaxy at high redshift

- ALMA-60 takes 24 hrs to detect CO in Milky Way galaxy at z=3- This becomes 55 hrs with ALMA-40, far from routine!- Will take 200 hrs to observe 4 objects

Gas kinematics in disksCO 3-2 in TW Hya disk with SMA

- constrain physical and chemical structure- constrain kinematics, radial and vertical turbulence- requires >50 hrs with ALMA-60 at highest spatial resolution

Linewidth < 1 km/s => need ~0.1 km/s resolution!

Obs

Mod

Qi et al. 2004

Imaging quality

- Image fidelity = model * beam / (reconstructed image – model * beam)- Simulation includes thermal noise, but not other types of noise- Single configuration image; M51 scaled to ~6” and observed at 0.1”

=> Image quality strong function of N

Simulations M. Holdaway

M51 H image

BCP discussion (cont’d)

2. Long baselines (>4 km): MA Long baselines are a level 1 science driver for ALMA

Imaging gaps on AU scale in protoplanetary disks Imaging CO lines in high-z galaxies (requires 3 mm band)

Some delay O.K., but should never be fully excluded; see ASAC March 2005 report

3+4: OSF facilities: PR/RE Don’t make OSF facilities too basic, since it may

hamper attracting astronomers to Chile

Protoplanetary disks

- Origin of gaps, rings and holes in debris disks => planet formation?- Typical integration times with ALMA 60 ~8 hr continuum-only

Augereau 2005

Protoplanetary disks

- More distant objects being discovered with Spitzer => ALMA follow-up

Beichman et al. 2004Rieke et al. 2005

MIPS 70 m

T

Need long baselines toimages gaps and perhaps

protoplanets in disks

Wolf & D’Angelo (2004)

Maximum baseline: 10 km, 850 GHz, t int=8h,

30deg phase noise

Mplanet / Mstar = 1.0MJup / 0.5 Msun

Orbital radius: 5 AU50 pc

100 pc

High-redshift galaxies CO at z=6.4

VLA

- Need long baselines to image CO at high-z at <0.2” resolution (4 km at 3 mm corresponds to 0.18’’)

Walter et al. 2004VLA and IRAM PdB

Walter et al. 2003

CO 3-2 map, SDSS J1148+5251

0.3’’

BCP discussion (cont’d)

5. WVR: MA WVR are critical for phase correction, even on baselines as short as

300 m, see ASAC October 2002 report Can significantly enhance efficiency of array

6a. Solar filters: MA Possible to defer half of solar filters Removal of solar filters would disenfranchise an entire community

6b. Quarter-wave plates: PR ¼ wave plate ensures higher precision on weak polarization signals,

but can be deferred 7a. Removal 1 IF: MA

Removal one 1 IF reduces sensitivity by 40% for continuum and most line projects, see ASAC March 2005 report

Phase Stability Variations

36° el.

Annual variation

Diurnal variation

night day

11.2

GH

z

<100 m needed to image to 0.2” at 345 GHz without phase correction

400

800

25%

75%

Weather statistics indicate that phase correction is almost always needed on baselines >300m, even with good transparency!!!

Transparency and phase stability

Median

Note tail in statistics of periods with good transparency but large phase rms ¬> phase correction essential!

WVRs correct phase on ~1 s timescale; fast switching on 10’s of seconds

BCP discussion (cont’d)

7b: Defer 2 of 4 subarrays: PR Defer 2 of 4 subarrays O.K., but array more efficient with 4 Can significantly affect Band 5 operation if only 2 subarrays

7c + 7d: ?? Need more technical information, especially on magnitude of phase

loss; not ready for scientific discussion

8: Defer 3 of 4 receiver bands: MA-U Receivers 6, 7 and 9 integral part of ALMA science, see ASAC

October 2004 and March 2005 reports

Motivation for at least 4 receiver bands

Coverage of CO and C+ lines over a large range of z

Dust SEDs, dust properties Ability to probe range in physical conditions

(10-1000 K, 102 – 109 cm-3) Ultimate spatial resolution at the highest

frequencies Large variety of molecules, hydrides

(out of 10 originally planned => major descope has already occurred)

Different lines probe different conditions

ncrit~23

Higher frequencytransitions probe higherdensities and temperatures

Band

9

763CO principle tracer

of H2 gas

Cold tenuous gas vs warm dense gas

CO excitation Milky Way galaxies different from starbursts

Milky Way galaxy

Starburst nucleus

Nearby Galaxy: NGC6090

HST: Dinshaw et a. 1999HST: Dinshaw et a. 1999 SMA: J. WangSMA: J. Wang

CO 2-1CO 2-1

CO 3-2CO 3-2

[C II] detection at z=6.4!

Maiolino et al. 2005

-Band 9: [C II] at z=1-1.5-Band 7: [C II] at z=4-6

BCP discussion (cont’d) 9: Drop one polarization: MA-U

Loss of one polarization leads to loss of sensitivity by 40%, see ASAC March 2005 report

10. Software descopes: MA-U Unacceptable as proposed; ALMA presented to

community as easy-to-use instrument, also for non-experts More modest savings could be discussed

11. - 12. Site testing: PR

Need to keep some minor funding for short testing campaigns

MA

U

U

U

MA50%

??

Defer

Small campaigns

Delay, but never excluded

Reduction comp. with 50 operating

U

Don’t make facilities too basic

ESAC iniitial reaction

Other ASAC charges

Charge 2: Time allocation procedure for large and/or joint projects ALMA needs large projects, but no need to

make formal distinction with small programs

Large programs should not start too soon (wait for array to have large fraction of its capabilities)

…….

Other ESAC topics Demonstration science: see upcoming ASAC report

Largely same as Science Verification in ESO terminology See updated schedule

ARC update: see report T. Wilson EU MC-RTN proposal: submitted Sept. 28; training students in

submm astronomy, i.p. interferometry ‘Star Formation throughout the Universe’ (led by S. Aalto)

EU ALMA workshops ALMA and modeling of galactic + extragalactic ISM, Sweden October

13-16 2005 Complex molecules/line surveys with ALMA, Denmark, May 8-10 2006

ALMA worldwide meeting, Madrid , November 2006

1.09 Science Summary Schedule20072006 20092008 20112010 2012

41 2 3 41 2 3 41 2 3 41 2 3 41 2 3 41 2 3 41 2 3

(Data from IPS as of 2005Oct06)

ATF Testing Support

OS

F/A

OS

Commissioning Antenna Array – Finish dates

16th 32nd 50th

Science Verification / Demonstration Science

AT

F

`

Dec ’09 Early Science

Feb ’09 Early Science Decision Point

Call for Proposals / Early Science Preparation

March 31 ’12 Start of Full Science

AOS 6 Ant Array

Evaluation Complete

8th

OSF Integration – Start dates

1st 16th 32nd 50th3rd2nd

SE

&I

Re

fere

nc

eATF Testing Prototypes & Pre-Production

8th

June ’06 ATF First Fringes

SC

IEN

CE

SU

MM

AR

Y Site Characterization

Science Support OSF

Subject to change!

Image quality (cont’d) ALMA-40 requires a different set of configurations

from zoomed spiral (e.g., rings or Y-shaped) Multi-configuration observations Different mode of operations

Array not continuously reconfigurable Risk of systematic errors (e.g. calibration) Long time scale for completion project Smaller number of objects

HD 141569 transitional disk: dust and cold gas

Augereau, Dutrey et al. 2004, in prep

When does gas disappear from disk? => constraints on time scalegiant planet formation

IRAM PdB12CO 2-1

Superposed onHST-STIS

Massive gas-rich disk

Debris disk

Redshifted CO with frequency bands

Starburstgalaxies

Milky-waygalaxies

Dust SEDs => photometric redshifts

P. Cox, priv. comm.

Band 6

Local CO 2-1 Bulk of medium excitation lines

Workhorse frequency for line observations in DRSP

Dust SED High-z CO at z=0.4-2.5 C+ at z=6-8

Band 3

Local CO 1-0 => tracer of cold gas Bulk of low excitation lines High-z CO at z=0-3 in MW galaxies

MW galaxy at z=3 has ~0.007 Jy km/s => requires 24 hr with full array to get 2 detection (calibration overheads?)

SiO 86 GHz maser

‘What science would be lost if band not or only partially available’

Band 7

Local CO 3-2 Bulk of medium excitation lines Dust SED and maps

Workhorse band for bulk of continuum observations in DRSP

Dust polarization High-z dust search C+ at z=4-6 H2D+ 372 GHz => cold clouds and disks with

heavy freeze-out

H2D+ in disks

TW HyaCSO data

DM Tau

Ceccarelli et al. 2004

Measuring the ionization degree in the midplane

- Expected strength ~4 K for 4” diameter disk => need to reach 0.4 K rms in <1 km/s bin at ~0.2” spatial resolution to image H2D+ => ~8 hr

Band 9

Local CO 6-5 High excitation lines Dust SED C+ at z=1.0-1.5 Ultimate spatial resolution

High excitation linesLocal starburst vs z=6.4 quasar

Bertoldi et al. 2003

Mapping warm gas in disks

AB Aur

LkCa15

-Optically thin lines ~few K => require 0.3 K rms on 0.1” scales to map

Van Zadelhoff et al. 2001, Dartois et al. 2003

Probing the radial and vertical temperature structure

Ultimate spatial resolution: Need for long baselines and Band 9

Massive gas-rich disks

Tenuous debris disks

gas + dust interstellar

-Driven by need to resolve protoplanetary disks on scales of 1 AU (1 AU at 140 pc = 7 marcsec)-Lines typically 10-50 K (optically thick) to few K (optically thin) => drives also sensitivity/collecting area