Cosmological QUOKKAS Towards an Asia-Pacific VLBI Network Jeffrey - - PowerPoint PPT Presentation

Cosmological QUOKKAS

Towards an Asia-Pacific VLBI Network

Jeffrey A. Hodgson Korean Research Fellow, KASI

with Sang-Sung Lee (KASI), Benjamin l’Hullier (KASI) and Ioannis Liodakis (Stanford)

Cosmological QUOKKAS

• Project to measuring the luminosity

distance-redshift relationship from 0 > z > 7

• “Standard speedgun”
• Requires high cadence
• Requires high-resolution
• Asked Samsung to fund the

conversion of Mopra telescope for conversion to KVN-style quasi-optics

○ Conditionally approved

2

~8000 km

Quasar observations using the KVN from Korea to Australia and Spain

?

Cosmological QUOKKAS

• Project to measuring the luminosity

distance-redshift relationship from 0 > z > 7

• “Standard speedgun”
• Requires high cadence
• Requires high-resolution
• A Quokka is a small marsupial on an island off

Perth

• Introduce some *very* preliminary results from

the project...

3

~8000 km

Quasar observations using the KVN from Korea to Australia and Spain

KVN high-z detection survey

• Observed ~140 sources on the KVN at 4 frequencies
• 2.5 < z < 6.21
• Took the VLBA fundamental catalog and any sources about

z>2.5 and 8 GHz flux density > 0.1 Jy

• Plus all z>4 quasars I could find (e.g. Coppejans 2017, EVN

symposia talks etc…)

• Made full use of phase-transfer: 30 mins integration at 3/2 mm !
• Fringe SNR=10 !
• Very surprising results

KVN high-z detection survey

• Sources detected as high as

z=5.95 @ 2mm

• Second highest redshift quasar

known (J1429+5447,z=6.21), detected at 14/7/3 mm

○ Orders of magnitude brighter than at cm-wave !

• Beyond z~4, *no* trend of

sources getting fainter

○ Implication that sources are getting intrinsically brighter as a function of redshift

Z Z

14mm 7mm 3mm 2mm

KVN high-z detection survey

• Observations approved to

follow up these results with KVN-Yebes

• Implications for high-z source

searches: are we looking in the wrong places?

• EAVN+Mopra+Yebes to image

these sources?

Z Z

14mm 7mm 3mm 2mm

Measuring distances to AGN using archival data

• Methods are still “secret”

○ Hopefully submit paper(s) soon….

• Arguably better than SNIa

○ We can constrain Hubble constant *and* Omega_m ○ In principle, can go from very nearby to very far away

• Testing our methods on archival BU 7mm VLBA data
• Case study in 3C 84
• Very preliminary results...

VERY Preliminary!

• Using BU (Jorstad

17) archival data

• Envelope appears

to follow the cosmology

• Due to low

cadence, seem to be underestimating slightly in some sources

VERY Preliminary!

• Using BU (Jorstad

17) archival data

• Envelope appears

to follow the cosmology

• Due to low

cadence, seem to be underestimating slightly in some sources Tendency towards lower H0, higher Omega_m, but not highly constrained at this stage

Distance to 3C 84

• Used the radio flare C3

after the major Gamma-ray

• utburst in 2015.81
• Luminosity distance:

○ 81 +/- 9 Mpc

• LCDM DL = 75 Mpc
• SN Ia 64 +/- 6 Mpc (Lennarz
• et. al. 2012)

The QUOKKA(S) Array

• High cadence observations of

the high-z sample

• Mopra for low-dec sources
• Yebes for high-dec sources
• Extremely high resolution

(~50 uas at 3mm)

• Unique NS baseline
• Mark6 and OCTAD backend
• rdered, test observations

early next year...

The QUOKKA(S) Array

• High cadence observations of

the high-z sample

• Mopra for low-dec sources
• Yebes for high-dec sources
• Extremely high resolution

(~50 uas at 3mm)

• Unique NS baseline
• Mark6 and OCTAD backend
• rdered, test observations

early next year...

Towards an Asia-Pacific VLBI Network

• Effectively a single-baseline
• Can we do more than just the

cosmology project?

• Limited imaging capabilities
• KaVA/EAVN with Mopra?

○ 22/43 single frequency

• Good for mid-dec sources

○ M87 ○ Sgr A* (may be resolved out…) ○ Cen A

Towards an Asia-Pacific VLBI Network

• Thailand will make imaging on

the array much better

• NS orientation has

implications for common visibility/high cadence obs.

• New Zealand?
• South Africa?
• Multi-frequency a must...

Conclusions

• High redshift (z>4) sources are considerably brighter than expected at

mm-wave and get intrinsically brighter as a function of redshift

• Derived an accurate distance to 3C 84, demonstrating how AGN can be

used as “standard speedguns”

• Very preliminary results showing that AGN appear to be useable for

measuring cosmology

• QUOKKAS array coming online soon to begin observations and persue

the project

• A future APVN would be very nice for imaging these sources...