frayer (1) redshifted molecular gas – evolution of galaxies david t. frayer (nrao) alma-band2 2013...

Frayer (1)

Redshifted Molecular Gas – Evolution of Galaxies

David T. Frayer (NRAO)

ALMA-Band2 2013

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/

Frayer (2)

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.

ALMA-Band2 2013

From the GBT 4mm Science Case

Frayer (3)

What are the Bright Extragalactic Lines?

ALMA Band-2 (67-90 GHz)Line Redshift Range12CO: 0.28<z<0.7213CO: 0.2<z<0.64 HCN: 0<z<0.32HCO+: 0<z<0.33

ALMA-Band2 2013

FCRAO RSR: NGC253+M82

Intermediate redshift galaxies and (1-0) transitions are important for understanding galaxy evolution

Frayer (4)

Star-Formation History from the Infrared

ALMA-Band2 2013

Magnelli, et al. 2009 (Spitzer FIDEL-70um result)

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.

ULIRGs

LIRGs

Frayer (5)

HST imaging of local IRAS LIRGs (part of GOALS sample – Great Observatories All-sky LIRG Survey)

ALMA-Band2 2013

What are LIRGs?--Diverse systems of mergers and disks

Frayer (6)

GBT/Zpectrometer CO(1-0)

ALMA-Band2 2013

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

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.

Why CO(1-0)?

Frayer (7)

VLA CO(1-0) Imaging

ALMA-Band2 2013

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

BzKs (Aravena et al. 2010)

SMGs (Ivison et al. 2010):

Why do we need spatial resolution?

Frayer (8)

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

ALMA-Band2 2013

Detection levels for same amount of observing time

Plot made in Aug 2012, before GBT 4mm upgrade

Frayer (9)

Evolution Disks vs “Merger” Starbursts

ALMA-Band2 2013

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.

Frayer (10)

Dense Gas in Local Galaxies

ALMA-Band2 2013

Gao & Solomon 2004: Dense gas traced by HCN better correlated with Lir than CO. SFE correlated with dense gas fraction. HCN & HCO+

Frayer (11)ALMA-Band2 2013

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

Kripps et al. 2008

Frayer (12)

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 et al. 1999

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

Frayer (14)ALMA-Band2 2013 Imanishi et al. 2007

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

Frayer (15)

Variations of Molecular Lines in

Nearby Galaxies, e.g. IC342 Meier & Turner 2005

ALMA-Band2 2013

IC342: CO=green, HI=red

Frayer (16)

16 element scalable W-band FPA for the GBT

ALMA-Band2 2013

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


GBT (9”)1pixel

GBT/ARGUS16pixel

GBT100pixel

ALMA1”

ALMA5”

ACA(23”)

ALMA-TP (70”)

Rms=1mJy/beam per point

2.5min 2.5min 2.5min 1.2min 1.2min 5hr 3hr

Rms=2mKper point

2.5min 2.5min 2.5min 122hr 11min 6min 3s

Map 3’x3’with 1mJy/beam

18hr 69min 11min 59min 59min 80hr 27hr

Map 3’x3’ with 2mK

18hr 69min 11min 6000hr 9hr 96min 27s

GBT vs ALMA Sensitivity: Estimated Observing Times

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


CASA Simulations to compare GBT vs ALMA+ACA+ALMA_TP30dor 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.


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 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 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.


ACA image:(9x7m dishes)

Shorter spacing recovers more of the emission.

Flux= 0.40 Jy(32% of total flux)


ACA+TP image:

Flux=1.16Jy(93% of total flux)

Note that TP adds significant flux outside of the known emission regions.


Comparisons of simulations of the 30Dor region (10” resolution).

GBT

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

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 (25)

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 (1) redshifted molecular gas – evolution of galaxies david t. frayer (nrao) alma-band2 2013...

Documents