ALMA: Capabilities and Status

Al Wootten

NRAO, ALMA/NA Project Scientist

ALMA is governed by a Board, with representatives from each of the partners (Chile, NSF/NRC, ESO/Spain, NINS) [~10 folks+]

Board committees include ALMA Science Advisory Committee (ASAC) [~14 folks], AMAC

ALMA construction activities are conducted by joint teams which report to the Joint ALMA Office (Tarenghi, Director; Beasley, Project Manager) in Santiago [four+]

Regional Managers, Project Scientists, Advisory Committees (e.g. NA, EU, JP ALMA Project Manager) ;

ANASAC, ESAC, JSAC Regional ALMA Resource Centers (ARCs) in partner

regions support users in the respective astronomical communities [NAOJ, NRAO, ESO]

Who is ALMA?

ALMA Observes the Millimeter Spectrum

Millimeter/submillimeter photons are the most abundant photons in the cosmic background, and in the spectrum of the Milky Way and most spiral galaxies.

Most important component is the 3K Cosmic Microwave Background (CMB)

After the CMB, the strongest component is the submm/FIR component, which carries most of the remaining radiative energy in the Universe, and 40% of that in for instance the Milky Way Galaxy.

ALMA range--wavelengths from 1cm to 0.3 mm, covers both components to the extent the atmosphere of the Earth allows.

COBE observations

Telescope altitude diam. No. A max (feet) (m) dishes (m2) (GHz)

NMA 2,000 10 6 470 250CARMA 7,300 3.5/6/10 23 800 250IRAM PdB 8,000 15 6 1060 250SMA 13,600 6 8 230 690eSMA 13,600 6/10/15 10 490 690 ALMA 16,400 12 505700 950ACA 16,400 7 12 460 950

Summary of existing and future mm/sub-mm Summary of existing and future mm/sub-mm arraysarrays

ALMA will have >6x more collecting area, and will be 10-100 times more sensitive and 10-100 times better angular resolution compared to current mm/submm telescopes

Contributors to the Millimeter Spectrum

In addition to dominating the spectrum of the distant Universe, millimeter/submillimeter spectral components dominate the spectrum of planets, young stars, many distant galaxies.

Cool objects tend to be extended, hence ALMA’s mandate to image with high sensitivity, recovering all of an object’s emitted flux at the frequency of interest.

Most of the observed transitions of the 142 known interstellar molecules lie in the mm/submm spectral region—here some 17,000 lines are seen in a small portion of the spectrum at 2mm.

However, molecules in the Earth’s atmosphere inhibit our study of many of these molecules. Furthermore, the long wavelength requires large aperture for high resolution, unachievable from space. To explore the submillimeter spectrum, a telescope should be placed at Earth’s highest dryest site.

Spectrum courtesy B. Turner (NRAO)

Forests of Spectral Lines

Schilke et al. (2000)

N

Where is ALMA?Where is ALMA?

El llano de Chajnantor

AOS TBToco

Chajnantor

Negro

MacónHonar

Road

43km=27 miles

Chascón

OSF

5000m Chajnantor site

ALMA

APEX

CBI

Site Char

Transparent Site Allows Complete Spectral Coverage

10 Frequency bands coincident with atmospheric windows have been defined.

Bands 3 (3mm), 6 (1mm), 7 (.85mm) and 9 (.45mm) will be available from the start.

Bands 4 (2mm), 8 (.65mm) and, later, some 10 (.35mm), built by Japan, also available.

Some band 5 (1.5mm) receivers built with EU funding.

Pwv = 0.5mm 15% of time

Receivers/Front Ends

ALMABand

Frequency Range

Receiver noise temperature

Mixing scheme

Receiver technolog

yTRx over

80% of the RF band

TRx at any RF

frequency

131.3 – 45

GHz17 K 28 K USB HEMT

2 67 – 90 GHz 30 K 50 K LSB HEMT

384 – 116

GHz37 K 62 K 2SB SIS

4125 – 169

GHz51 K 85 K 2SB SIS

5163 - 211

GHz65 K 108 K 2SB SIS

6211 – 275

GHz83 K 138 K 2SB SIS

7275 – 373

GHz147 K 221 K 2SB SIS

8385 – 500

GHz98 K 147 K DSB SIS

9602 – 720

GHz175 K 263 K DSB SIS

10787 – 950

GHz230 K 345 K DSB SIS

• Dual, linear polarization channels:•Increased sensitivity•Measurement of 4 Stokes parameters

•183 GHz water vapour radiometer:•Used for atmospheric path length correction

Antennas Demanding ALMA antenna

specifications: Surface accuracy (25 µm) Absolute and offset pointing accuracy

(2 arcsec absolute, 0.6 arcsec offset) Fast switching (1.5 deg sky in 1.5 sec) Path length (15 µm non-repeatable,

20 µm repeatable)

To validate these specifications: two prototype antennas built & evaluated at ATF (VLA)

Prototype Antenna Testing at VLA

Photogrammetry,January 2005

Antenna Configurations (min)

150 m

ALMA + ACA

First ACA 12m – Dec 2007, 7m – Nov 2008

Big tractor picture These vehicles must lift the 110 ton

antenna systems and transport them over the ALMA road, often for several tens of kilometers at 7% avg grade, to and from the antenna stations and the OSF. To do this, these vehicles are equipped with twin 1340 horsepower engines; the

transporters measure 33 feet wide, 52 feet long, and 15 feet

high.

10,000m

4 mas @ 950 GHz

Antenna Configurations (max)

Site infrastructure (AOS/OSF) + inner array completed 2008

Summary of detailed requirements

Frequency 30 to 950 GHz (initially only 84-720 GHz fully instrumented)

Bandwidth 8 GHz, fully tunable

Spectral resolution 31.5 kHz (0.01 km/s) at 100 GHz

Angular resolution 30 to 0.015” at 300 GHz

Dynamic range 10000:1 (spectral); 50000:1 (imaging)

Flux sensitivity 0.2 mJy in 1 min at 345 GHz (median conditions)

Antenna complement 64 antennas of 12m diameter, plus compact array of 4 x 12m and 12 x 7m antennas (Japan)

Polarization All cross products simultaneously

Schedule

June 1998Phase I: Design & Development

November 2001Prototype antennas at VLA site

December 2001US/European ALMA Agreement

September 2004Enhanced ALMA Agreement (JP)

2005 Antenna Contract Awarded

2005-7 Prototype System Testing

2007-8 AOS/OSF completed

2009 - 2010Commissioning & early science operations

2012 Full Operations

Evaluation of Early Science

Array Complete

Projected 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 as of 2006Aug06)

ATF Testing Support

OS

F/A

OS

Commissioning Antenna Array – Finish dates

16th 32nd 50th

Science Verification

AT

F

`

July ’10 Early Science (+24)

Sept ’09 Early Science Decision Point

Call for Proposals / Early Science Preparation

Sept ’12 Start of Full Science

8th

OSF Integration – Start dates

1st 16th 32nd 50th3rd2nd

SE

&I

Re

fere

nc

eATF Testing

8th

Nov ’06 ATF First Fringes

SC

IEN

CE

SU

MM

AR

Y

Site Characterization

Science Support OSF

Time Now

March ’09 Limited call for SV proposals

+6 antennas

NOT YET BOARD APPROVED

3rd

Highest Level Science GoalsBilateral Agreement Annex B:“ALMA has three level-1 science requirements: 1) The ability to detect spectral line emission from CO or C+ in a

normal galaxy like the Milky Way at a redshift of z = 3, in less than 24 hours of observation.

2) The ability to image the gas kinematics in a solar-mass protostellar/ protoplanetary disk at a distance of 150 pc (roughly, the distance of the star-forming clouds in Ophiuchus or Corona Australis), enabling one to study the physical, chemical, and magnetic field structure of the disk and to detect the tidal gaps created by planets undergoing formation.

3) The ability to provide precise images at an angular resolution of 0.1". Here the term precise image means accurately representing the sky brightness at all points where the brightness is greater than 0.1% of the peak image brightness. This requirement applies to all sources visible to ALMA that transit at an elevation greater than 20 degrees. These requirements drive the technical specifications of ALMA. “

A detailed discussion of them may be found in the new ESA publication Dusty and Molecular Universe on ALMA and Herschel.

ALMA Design Reference Science Plan(DRSP)

Goal: To provide a prototype suite of high-priority ALMA projects that could be carried out in ~3 yr of full ALMA operations

Started planning late April 2003; outline + teams complete early July; submitted December 2003; updated periodically

128 submissions received involving ~75 astronomers Review by ASAC members completed; comments

included Current version of DRSP on Website at:

http://www.strw.leidenuniv.nl/~alma/drsp.html New submissions continue to be added.

Frequency band capabilities

Band 3: 84-116GHz. FOV = 60 arcsec Continuum: ff/dust separation, optically-thin dust, dust emissivity

index, grain size SiO maser, low excitation lines CO 1-0 (5.5K), CS 2-1, HCO+ 1-0,

N2H+…

Band 6: 211-275GHz. FOV = 25 arcsec Dust SED Medium excitation lines: CO 2-1 (16K), HCN 3-2, …

Band 7: 275-373GHz. FOV = 18 arcsec Continuum: most sensitive band for dust. Wave plate at 345GHz for precision polarimetry Medium-high excitation lines: CO 3-2 (33K), HCN 4-3, N2D+, …

Band 9: 602-720GHz. FOV = 9 arcsec Towards peak of dust SED, away from Rayleigh Jeans; hence T(dust) High excitation lines e.g. CO 6-5 (115K), HCN 8-7 in compact

regions

12m

Aperture Synthesis with ALMA12-m cross-correlations from 60 dishes measure spacings from 12m up to maximum baseline e.g. 10km

Auto-correlations from 4 12-m dishes measure from zero up to ~6m spacings

Extra measurements here help imaging precision:

• Cross-correlations from 7-m dishes, or

• Large single dish observationsUp to 15km

Initial Conditions: Pre-collapse Cores

L1498: Tafalla et al.

Strong chemical gradients and clumpiness

Indicates depletion and chemical evolution

ALMA mosaic at 3mm: 100 pointings plus single-dish data needed

ALMA can resolve 15AU scales in nearby cores, or study cores at 1000AU scales out to 10kpc

Core dynamics: infall

Di Francesco et al (2001)

Small-scaleExtended 0.1 - 0.3 pc

Walsh et al

Starless Core Chemistry: probing the depletion zones

Complete CNO depletion within 2500AU?

ALMA can study this region, in objects as far as the GC, in H2D+

CS, CO, HCO+

NH3, N2H+

H2D+

D2H+

Walmsley et al. 2004; Caselli et al 2003

372GHz line8,000AU

2,500AU

15,000AU

Polarized CO Line Emission

NFC1333IRAS4A Goldreich-Kylafis

Effect

Girart, Crutcher, Rao 1999

SiO J=1-0 Choi 2005

A1

A2

Polarization and the Role of Magnetic Fields

Girart, Rao, Marrone 2006

•Polarization hole•Polarization peak is offset•Hour glass shape of the magnetic field structure in the circumbinary envelope•The large scale field is well aligned with the minor axis•We will need some higher angular resolution observations to map the structure of the field between the two cores

•Contours - I•Pixel - polarized flux density sqrt(Q^2+U^2)•RMS = 3 mJy/bm•Peak pol = 9 % at PA 153 degrees•At the peak of Stokes I - pol = 1%•Averaged pol = 4.7% @ 145 degrees

E-Vectors

B-Vectors

The data indicate that, in the case of IRAS 4A, magnetic pressure is more influential than

turbulence in slowing star formation within the cloud core. The same likely is true for similar

cloud cores elsewhere.

Star formation in crowded environments

ALMA can resolve 15AU scales at Taurus

Clump mass function down to 0.1 Jupiter masses

Onset of multiplicity

BD formation Internal structure

of clumps Turbulence on AU

scales

Bate 2002

Protostars and Clumps in Perseus: Hatchell et al 2005.

Cores and Filaments: Are Hydrodynamical Simulations Realistic? Clump mass

spectrum Relation to IMF? Low mass limit? Dependence on

age? Clump structure –

transient or bound? Filaments

are they omnipresent?

thermal/density structure

Motte et al

Klessen 2004

Molecular Outflows

Origin of flows down to 1.5AU scales

10 mas resolution at 345 GHz: 24 hours gives 5K rms at 20

km/s resolution Resolve magnetosphere: X or

disk winds? Flow rotation?

Proper motions 0.2 arcsec per year for 100km/s

at 100pc Resolve the cooling length

Resolve multiple outflow regions

Beuther et al, 2002

Chandler & Richer 1999

170AU resolution

Spatially-resolved Spectral Surveys

8GHz bandwidth

Schilke et al

Kuan

et a

l 200

4

Kuan

et a

l 200

4

Loon

ey e

t al,

2000

“Hot Core” chemistry around low mass protostars

300AU sized molecular structures around protostellar candidates

Different chemical signatures

= 333m = 870m

Mplanet / Mstar = 0.5MJup / 1.0 Msun

Orbital radius: 5 AU

Disk mass as in the circumstellar disk as

around the Butterfly Star in Taurus

Maximum baseline: 10km,

tint=8h,

30deg phase noise

pointing eror 0.6“

Tsys = 1200K (333mu) / 220K

(870mu)Sebastian Wolf (2005)

50 pc

50 pc

100 pc

“Debris” disk spectroscopy with Spitzer

Rieke et al 2004

“Debris” Disk imaging with ALMA

Wyatt (2004) model: dust trapped in resonances by migrating planets in disk

ALMA will revolutionise studies of the large cold grains in other planetary systems

Vega (Holland et al)Fom

alhaut (Greaves et al)

Science group suggestions:

* predictions about how gas lifts off of the surface of the disk and what the physical conditions of that gas might be - we need to know what tracers ALMA can use are likely to probe this effect and how those tracers are likely to evolve as the protostar heats up or for higher luminosity protostars. * when the material accretes from the "envelope" to the disk and starts to "pile-up” in the disk (in the scenario for episodic accretion), there should be a second, lower energy accretion shock in the outer disk. What are the atomic/molecular/continuum diagnostic of that shock? Any chance we could observe it with ALMA?

www.alma.info

The Atacama Large Millimeter Array (ALMA) is an international astronomy facility. ALMA is a partnership between Europe, North America and Japan, in cooperation with the Republic of Chile. ALMA is funded in North America by the U.S. National Science Foundation (NSF) in cooperation with the National Research Council of Canada (NRC), in Europe by the European Southern Observatory (ESO) and Spain. ALMA construction and operations are led on behalf of North America by the National Radio Astronomy Observatory (NRAO), which is managed by Associated Universities, Inc. (AUI), on behalf of Europe by ESO, and on behalf of Japan by the National Astronomical Observatory of Japan.