1. A Search for water masers in High-redshift un-beamed AGNs: T. Ghosh, S
A Search for water masers in High-redshift un-beamed AGNs: T.Ghosh, S.Mathur (OSU), C.J. Salter
Motivation: Water maser in NGC A Seyfert2 galaxy
Green – Optical
Blue – Radio
Red - X-ray
Distance = 7.2 Mpc
BH Mass = 3.78 x 107 Mo
Search & follow-up observations in external galaxies have now become key
projects for some existing (GBT, EFF, EVLA, VLBI) and upcoming telescopes (ASKAP & SKA) e.g. the Megamaser Cosmology Project -- Braatz et al., WMCP -- Greenhill et al.

2. --Motivation- contd....
Detection Statistics: As of Jan, 2014, 22-GHz maser emission has been detected in 162 galaxies, out of ~2700 searched (detection rate of ~6%).
Most of these are Seyfert-2 type galaxies.
Most are nearby objects within velocities ~10,000 km/s (z=0.03). Only three “high-z” objects, at z=0.6, 2.2 & 2.4 were added recently, all in Gravitational-lens systems.
Goal: We wanted to extend the search to redshift ranges of 1.22 – 1.78 and 2.71 – 4.5 for which the rest-frame transition frequency of 22-GHz would fall within the pass-bands of Arecibo’s X- and C-band receivers.
For any detected objects, follow up observation would help in extending direct exploration of AGN models and cosmological parameters to
higher z.

3. Conditions for 22-GHz Water maser emission
The transition is between the energy levels of
These states lie ~645 K above the ground state,and the kinetic temperature of the gas should be > 300K to populate these. Collisional population
inversion requires densities >107 /cc.
Such conditions can occur close to
the AGN in obscuring molecular
torus.
Likely to be seen in Type2 AGNs

4. Sample Selection & Observation:
We selected sources satisfy one or more of the following criteria:
(1) Soft X-ray absorption,
(2) Narrow optical emission lines (these narrow line radio galaxies are the radio-loud counterparts of Seyfert 2 galaxies),
(3) Steep radio spectrum,
(4) Compact edge-brightened (FRII) radio morphology (angular size < 30′′, so that they are not heavily resolved by the Arecibo X-band beam).
Together, these criteria ensure that these radio AGNs are viewed roughly edge-on. Also included were 3 other objects of special interest (NLRG, Grav. Lens, & ERO), making 46 galaxies in our sample.
Our total-power position-switched observations used the InterimCorrelator, recording 50-MHz bandwidth centered at the redshifted frequency of the 22-GHz transition. Integration times varied due to scheduling constraints. The brightness scale was established via the noise-diode calibration and the telescope's standard Gain curves (K/Jy). Most of the spectra were RFI-free.

5. Results -1
No detected emission:

6. Results – 1 (Contd: with updated z)
Updated z for 11/46 galaxies implies that the line was outside the passband.

7. Result – 2: Absorption (?)

8. Jet-Torus Interaction?

9. Conclution & Future Work
Poor detection rate may be mainly due to a combination of poor sensitivity and water-maser luminosity function.
Need to extend the search down to a uniform sensitivity limit over the z-range. The new wider-band spectrometer – new C-band Rx, better source selection via improved redshifts including gravitational lenses should be useful.
Absorption in B will be verified (new proposal awaiting review) – if true and truly variable – imaging with VLBI will help study this possible jet- torus interaction, a far off analog of NGC660 ?