Redshifted Molecular Gas – Evolution of Galaxies David T. Frayer (NRAO) ALMA Band-2 (68-90 GHz) is a crucial missing band for astronomy. Before the GBT 4mm system, there was very limited sensitivity coverage below 80 GHz. http://www.gb.nrao.edu/4mm/ ALMA-Band2 2013 Frayer (1)

ALMA Band-2 (4mm Rx)

“

Key Science

” • • • •

Fundamental Physics –

With VLBI, probe the physics near the base of black hole jets in nearby galaxies {and measure the size of the galaxy via parallax of SagA*}.

The Context of Star Formation –

Deuterium species and dense gas tracers key for studies of cold cloud cores from which stars form.

Origin of Life –

Complex organic molecules and pre-biotic molecules in the ISM and comets which are key for studying the conditions from which life eventually forms (unexplored frequencies --- lots of discovery potential in astro/bio-chemistry).

Galaxies Across Cosmic Time –

CO(1-0) at intermediate redshifts where the evolution of galaxies is proceeding rapidly and dense gas tracers, such as HCN and HCO+, in local star forming galaxies.

From the GBT 4mm Science Case ALMA-Band2 2013 Frayer (2)

What are the Bright Extragalactic Lines?

ALMA Band-2 (67-90 GHz) Line Redshift Range 12CO: 0.28

13CO: 0.2

HCO+: 0

Intermediate redshift galaxies and (1-0) transitions are important for understanding galaxy evolution ALMA-Band2 2013 FCRAO RSR: NGC253+M82 Frayer (3)

Star-Formation History from the Infrared

Why are LIRGs important?

The bulk of the infrared EBL is at z~1, and the rapid evolution from now to z~1 is associated luminous infrared star-forming galaxies (LIRGs). Herschel and Spitzer Surveys found large numbers of z~0.2-1 LIRGS.

 CO at intermediate redshifts key.

ALMA-Band2 2013 LIRGs ULIRGs Magnelli, et al. 2009 (Spitzer FIDEL-70um result) Frayer (4)

HST imaging of local IRAS

LIRGs

(part of GOALS sample – Great Observatories All-sky LIRG Survey) What are LIRGs?

- Diverse systems of mergers and disks ALMA-Band2 2013 Frayer (5)

GBT/Zpectrometer CO(1-0)

Why CO(1-0)?

GBT/Zpectrometer CO(1-0) and CARMA/PdBI CO(3 2) observations of Herschel SMGs show wide range of L ’[CO](3-2/1-0) ratios of ~0.6+/-0.4  Need 1-0 line for molecular mass measurements.

ALMA-Band2 2013 H-ATLAS SDP.81(ON)+SDP.130 (REF, negative): CO(1-0) redshifts measured. (Frayer et al. 2011) Frayer (6)

Why do we need spatial resolution?

VLA CO(1-0) Imaging

SMGs (Ivison et al. 2010): BzKs (Aravena et al. 2010) Observations suggest low-CO excitation for both the BzK ’ s and SMG samples  extended cold CO(1-0)? Imaging: Extended emission or separated clumps, outflows, disks, structure/kinematics  ALMA ALMA-Band2 2013 Frayer (7)

Comparison of ALMA,VLA, and the GBT for redshifted CO(1-0)

Detection levels for same amount of observing time Plot made in Aug 2012, before GBT 4mm upgrade ALMA-Band2 2013 Frayer (8)

Evolution Disks vs

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Merger

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Starbursts

Daddi et al. 2010b BzK ’ s and Tacconi et al. 2010 disk selected sample compared with the SMGs.

With CO(1-0) at intermediate redshift, ALMA-Band-2 can study the molecular mass evolution of the “disk sequence” in the transition epoch between z~0--1.

ALMA-Band2 2013 Frayer (9)

Dense Gas in Local Galaxies

Gao & Solomon 2004: Dense gas traced by HCN better correlated with Lir than CO.

SFE correlated with dense gas fraction.



HCN & HCO+

ALMA-Band2 2013 Frayer (10)

Significant HCO+/HCN variations in starbursts and AGN sources, although tracing similar densities.

Kripps et al. 2008 ALMA-Band2 2013 Frayer (11)

ALMA mapping CO, HCN, HCO+

• • • (HCN & HCO+)/CO  measures dense gas fraction, star-formation efficiency HCN/CO strong enhancements  AGN, extremely compact IR sources (x-ray heating, IR pumping) HCO+/HCN ratio enhanced in star-forming regions (UV-field, SN shocks) ALMA-Band2 2013 Frayer (12)

Local example: VV114 merger system shows molecular gas and dust that peaks between the two main optical components. The mid-IR emission peaks on the extremely red J-K source in VV114 East ALMA-Band2 2013 Frayer et al. 1999 Frayer (13)

HCO+ peaks on the star-forming regions with the CO and dust between VV114E&W, while HCN peaks on the strong mid-IR/extremely red VV114E component ALMA-Band2 2013 Imanishi et al. 2007 Frayer (14)

Variations of Molecular Lines in Nearby Galaxies,

e.g. IC342 Meier & Turner 2005 IC342: CO=green, HI=red ALMA-Band2 2013 Frayer (15)

16 element scalable W-band FPA for the GBT

Argus

is scheduled to be deployed at the GBT by November 2014 and is a collaboration between Stanford U. (PI Sarah Church), Caltech, JPL, Univ. Maryland, Univ. Miami, and NRAO.

Frequency operation range: 75-115.3 GHz Tsys~75K ALMA-Band2 2013 Frayer (16)

GBT vs ALMA Sensitivity: Estimated Observing Times

Rms=1mJy/ beam per point Rms=2mK per point

GBT (9”) 1pixel

2.5min

2.5min

GBT/ARGUS 16pixel

2.5min

2.5min

Map 3’x3’ with 1mJy/beam Map 3’x3’ with 2mK 18hr 18hr 69min 69min

GBT 100pixel

2.5min

2.5min

11min 11min

ALMA 1”

1.2min 1.2min

122hr 59min

ALMA 5”

11min 59min 6000hr 9hr

ACA (23”)

5hr 6min 80hr 96min

ALMA-TP (70”)

3hr 3s 27hr 27s Interferometers provide high-resolution data and good point source sensitivity (mJy/beam), but lack sensitivity to extended emission (mK).

ALMA-Band2 2013 Frayer (17)

CASA Simulations to compare GBT vs ALMA+ACA+ALM A_TP

30dor 8um IRAC image – Rescaled from 2 ” pixels to 1 ” pixels.

30dor in the LMC is the most luminous star-formation region in the local group of galaxies.

ALMA-Band2 2013 Frayer (18)

GBT simulated HCN image: Total flux: 1.25 Jy Contours are (0.05, 0.1, 0.2, 0.4, 0.6, 0.8) x peak.

ALMA-Band2 2013 Frayer (19)

ALMA 5 ”image (50x12m dishes, full ALMA) Flux: 0.084 Jy (7% of total flux) Contours (-0.1, 0.05, 0.05, 0.1, 0.2, 0.4, 0.6, 0.8)xpeak ALMA-Band2 2013 Frayer (20)

ALMA in Total Power Mode (4x12m dishes OTF maps) Note the lack of spatial information…. Not very useful for combining with data taken with ALMA ’s resolution. ALMA-Band2 2013 Frayer (21)

ACA image: (9x7m dishes) Shorter spacing recovers more of the emission.

Flux= 0.40 Jy (32% of total flux) ALMA-Band2 2013 Frayer (22)

ACA+TP image: Flux=1.16Jy

(93% of total flux) Note that TP adds significant flux outside of the known emission regions.

ALMA-Band2 2013 Frayer (23)

Above: ALMA using ACA+TP for clean model does well for bright central regions, but has edge effects and misses extended emission.

ALMA-Band2 2013 Comparisons of simulations of the 30Dor region (10 ” resolution). GBT Above: ALMA “feathered” with ACA+TP adds in extended emission throughout the map and does not do as good as job with bright central region.

Frayer (24)

Concluding Remarks

• ALMA Band-2 Extragalactic Science:



Galaxy evolution via CO(1-0) at intermediate/low redshifts



Dense gas (HCN & HCO+) and molecular variations in nearby and redshifted starbursts • Technical synergies of 67—116 GHz (ALMA Band-2+3 and GBT W-FPA development) • GBT W-FPA could provide useful short space data for ALMA images of extended sources

ALMA-Band2 2013 Frayer (25)