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 Quasar observations using the KVN from Korea to Australia and Spain ~8000 km ● 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
Cosmological QUOKKAS Quasar observations using the KVN from Korea to Australia and Spain ~8000 km ● 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
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 14mm 7mm ● 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 ○ 3mm 2mm at cm-wave ! Beyond z~4, *no* trend of ● sources getting fainter Implication that sources are getting ○ intrinsically brighter as a function of Z Z redshift
KVN high-z detection survey Observations approved to 14mm 7mm ● follow up these results with KVN-Yebes Implications for high-z source ● searches: are we looking in the wrong places? 3mm 2mm EAVN+Mopra+Yebes to image ● these sources? Z Z
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 Tendency towards lower H0, Due to low ● higher Omega_m, but not highly cadence, seem to constrained at this stage be underestimating slightly in some sources
Distance to 3C 84 Used the radio flare C3 ● after the major Gamma-ray outburst 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 ● ordered, 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 ● ordered, 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... ●
Recommend
More recommend
