The ALMA Wideband Sensitivity Upgrade
John Carpenter
Joint ALMA Observatory

ALMA - ASTE - 45m Users Meeting 2022
December 20-21, 2022

ALMA Capabilities
Imaging

Spectroscopy

8 receiver bandsContinuum

Polarization

VLBI

New facilities in the next decade
ESO 39 meter
JWST

TMT 30 meter

GMT 25 meter

Nancy Grace Roman
Telescope

ALMAVera Rubin TelescopengVLA

ALMA Development Program
Dedicated funds to enhance ALMA as a world-leading submillimeter facility

Hardware

Software

Infrastructure

ALMA Development Roadmap

ALMA2030 Development Priorities
Receiverbandwidth

Expand bandwidth by at least a factor of twoSciencearchive

Optimize archive science

Angularresolution

Collectingarea

Widefield
mappingYTIROITOP PR

Extend baselines by a factor of 2-3

Develop science cases for increasing the number of 12-m antennas

Study science case and technical feasibility of focal plane arraysWideband Sensitivity Upgrade (WSU)• Upgrade of the bandwidth and throughput of the ALMA system- upgraded receivers with increased bandwidth and improved receiver temperatures- more powerful correlator- increased data reduction capacityUpgrade!
AntennasReceivers

Back end

CorrelatorData processingArchives

Astronomers

Wideband Sensitivity Upgrade: Overview• Available bandwidth• Correlated bandwidth• Observing speed

ALMA 2030 (goal)
ALMA 2030
Under development

Band 2Band 6Goal

Current receivers

Band 1Band 3
Band 4
Band 5
Band 6
Band 7
Band 8Band 9Band 10} DSB
0816

24

Available instantaneous bandwidth per polarization (GHz)

Factor of 2-4 increase in the available IF bandwidth.

32

Wideband Sensitivity Upgrade: Overview• Available bandwidth• Correlated bandwidth• Observing speed

Band 1Band 2Band 3
Band 4
Band 5Band 6Low spectral resolution
High spectral resolution

Band 7Band 8Band 9Band 1002040
Factor increase in correlated bandwidthHigh spectral resolution ~ 0.1 km/s

6080

Wideband Sensitivity Upgrade: Overview• Available bandwidth• Correlated bandwidth• Observing speed

Increase in Band 6 observing speed with ALMA 2030
Observing mode

Increase in speed over current system*Continuum

4.8x (with goal of 9.6x)

Spectral line

2.2-4.7x* To reach same sensitivity as current system with single tuning

Increase in observing speed results from• improved receiver temperatures• improved digital efficiency• wider bandwidth (continuum)Spectral scans will see further speed increases due to larger correlated bandwidth.

The power of molecular spectroscopy in disks
HD 163296
Dust• Gas mass
- dust traces only ~ 1% of the total disk mass
- use molecules to trace the dominant disk component (H2)
• Chemistry and the chemical compositions of planets• 3D velocity and temperature structure of disks• Detect embedded planets through velocity distortions• With vastly improved spectral grasp and improved line (and continuum!) sensitivity,
the Wideband Sensitivity Upgrade will be a tremendous advance for disk studies.

Öberg et al. (2021)

The WSU Advantage

c-C3H23(3,0)-2(2,1)

The WSU Advantage

c-C3H23(3,0)-2(2,1)

The WSU Advantage

c-C3H23(3,0)-2(2,1)

Band 6v2 IF=12 GHz

The WSU Advantage

c-C3H23(3,0)-2(2,1)

Band 6v2 IF=12 GHz

The WSU Advantage
DCO+J=3-2

NO
J=5/2-3/2

SO2SO3Hc-C
22
10(5,5)-11(4,8)
3(3,0)-2(2,1)

H2S
2(2,0)-2(1,1)

SiOJ=5-4

c-C3H26(0,6)-5(1,5)

HC3N
J=24-23

H2CO
3(2,1)-2(2,0)

C15N
N=2-1

SO
3Σ 6(5)-5(4)11(1,11)-10(0,10)

C17O
J=2-1

t-HCOOH
10(4,6)-9(4,5)

H2CO
3(1,2)-2(1,1)

H2CS
7(0,7)-6(0,6)

H2CS
7(1,6)-6(1,5)

CN
N=2-1

c-C3H24(3,2)-3(2,1)

c-C3H23(2,1)-2(1,2)

CS
J=5-4

HC3N
J=25-24

HC3N
J=27-26

13CS

C34S
J=5-4

t-HCOOH

SO3Σ 2(3)-3(2)c-C3H25(2,3)-4(3,2)

SO
3Σ 5(6)-4(5)SO3Σ 8(9)-8(8)HCIF=123N GHzBand 6v2

c-C3H25(3,3)-4(2,2)

HC18O+
J=3-2

J=5-4

11(2,10)-10(2,9)… and up to 40 additional spectral windows!

J=28-27

Star formation
Envelope
DCO+

Hot core
HCOOHHigh velocity jet
SiO

Low-velocity flow
COCentrifugal barrier
CCHSputtering
CH3OH

Class I

Outflow cavity
CCH

300 AUClass II

Sakai et al. (2017)
Tychoniec et al. (2021)

Molecular probes of star formation with ALMA 2030

Tychoniec et al. (2021)

Molecular probes of star formation with ALMA 2030

Tychoniec et al. (2021)

Efficient spectral scans of protostars• PILS survey of IRAS 16293 protostar required 18 tunings• ALMA 2030 will need only 2 tunings!
Jørgensen et al. (2016)

ALCHEMI survey of NGC 253
ALMA 2030 (goal)
ALMA 2030
Current system• Survey speed with ALMA 2030 will increase by a factor of 3-6 plus any gains fromimproved receiver temperatures.

Martín, Harada et al. (2021)

Probing the origins of galaxies

MACS1149-JD
zphot = 9.44 ± 0.12

• Candidate galaxy at photometric redshift of z=9.4• Universe only 500 Myr old!
• Spectroscopy needed to determine redshift- large uncertainties- contaminants at lower redshift

Zheng et al. (2017)
McLead et al. (2016)

ALMA spectral scan search for Oxygen in MACS1194-JD

zphot = 9.44
Redshiftprobability
distribution

ALMA spectral scan search for Oxygen in MACS1194-JD
z=9.11

zphot = 9.44

zspec = 9.11

Redshiftprobability
distribution

Hashimoto et al. (2018)

ALMA spectral scan search for Oxygen in MACS1194-JD
z=9.11

zphot = 9.44

zspec = 9.11

Redshiftprobability
distribution• ALMA 2030 upgrade will be at least 3 times fasterplus any improvements from lower receiver noise
Hashimoto et al. (2018)

Summary• Technical upgrades- Available bandwidth : factor of 2-4 increase- Correlated bandwidth : more than an order of magnitude increase with ~ 0.1 km / s resolution- Observing speed: 2.2-4.7x faster for spectral lines, 4.8x faster for continuum (Band 6 upgrade)• Scientific impact- Planet formation : comprehensive studies of physical, kinematic, and chemical structure of disks- Star formation: efficient surveys of all stages in the star formation process- Galaxy formation : probe the formation and evolution of galaxies across cosmic time
• Timeline- Band 1: available starting in Cycle 10- Band 2: expecting production to start in 2023

- Band 6: prototype under development- Correlator : 5 years for construction and commissioning- Digital Transmission System (DTS): East Asia project approved by ALMA Board in November 2022
- Digitizers : European project approved by the ALMA Board- Upgrade of most other receiver bands are under study

ALMA Memo 621
arXiv 2211.00195