\documentclass[11pt]{article}
\usepackage{graphicx}
\usepackage{natbib}
\usepackage{color}
\usepackage{fancyhdr}
\usepackage[linktocpage=true]{hyperref}
\hypersetup{
            colorlinks=true,
            linkcolor=black,
            filecolor=black,
            citecolor=black,
            urlcolor=blue
           }
%%
%%   First draft: 2018.02.18_10:33:02
%%   Last  draft: 2018.02.21_21:43:35
%% 
\input mace.tex
\newcommand{\pid}   {\par\hangindent=2em\hangafter=-9\noindent}
\newcommand{\ppid}  {\par\hangindent=4em\hangafter=-9\noindent}
\newcommand{\pppid} {\par\hangindent=6em\hangafter=-9\noindent}
\newcommand{\ppppid}{\par\hangindent=8em\hangafter=-9\noindent}
%\newcommand{\nthr}[1]{ \multicolumn{3}{ @{} l }{#1} }
\renewcommand{\epsilon}{\varepsilon}
\renewcommand{\phi}{\varphi}
\newcommand{\dint}{\int\hspace{-0.25em}\int}
\newcommand{\sinc}{\rm sinc }
\newcommand{\hh}{\hphantom}
\newcommand{\hp}{\hphantom{+}}
\newcommand{\vex}{\vspace{1ex}}
\newcommand{\vhex}{\vspace{0.5ex}}
\newcommand{\den}{\Frac{1}{c}\Frac{1}{1 + \Frac{1}{c}\lp \vec{V_{\earth}}(t_1)\, + \dmat{E}(e(t_1))\,\vec{r}_2\rp} }
\newcommand{\jgr}{Jour. Geophys. Res.}
\newcommand{\grl}{Geophys. Res. Let}
\renewcommand{\refname}{\par\vspace{-2ex}\par}
%\definecolor{Dblue}{rgb} {0.152,0.268,0.720}
\definecolor{Dblue}{rgb}{0.070,0.070,0.312}
\definecolor{Dgreen}{rgb}{0.094,0.410,0.094}
\definecolor{Dred}{rgb}{0.312,0.070,0.070}
\newcommand{\Grb}[1]{\textcolor{Dgreen}{\bf #1}}
\newcommand{\Blb}[1]{\textcolor{Dblue}{\bf #1}}
\newcommand{\Rdb}[1]{\textcolor{Dred}{\bf #1}}
% \definecolor{LightSiren}{rgb}{0.918,0.867,1.000} % too light
% \definecolor{LightGreen}{rgb}{0.918,1.000,0.867} % too light
\definecolor{LightSiren}{rgb}{0.900,0.850,0.980}
\definecolor{LightGreen}{rgb}{0.900,0.980,0.850}
\newcommand{\vx}{\vspace{1ex}}
\newcommand{\bss}{\hspace{-2em}}
\newcommand{\web}[1]{\Blb{\url{#1}}}
\renewcommand{\topfraction}{0.95}
\renewcommand{\bottomfraction}{0.95}
\renewcommand{\textfraction}{0.05}
\newcommand{\Fermi}{{\it Fermi}}

\makeatletter\newenvironment{sirenbox}{%
       \noindent
       \begin{lrbox}{\@tempboxa}\begin{minipage}{0.99\columnwidth}}{\end{minipage}\end{lrbox}%
       \colorbox{LightSiren}{\usebox{\@tempboxa}}
}\makeatother
\makeatletter\newenvironment{greenbox}{%
       \noindent
       \begin{lrbox}{\@tempboxa}\begin{minipage}{0.99\columnwidth}}{\end{minipage}\end{lrbox}%
       \colorbox{LightGreen}{\usebox{\@tempboxa}}
}\makeatother


\voffset    = -20mm
\hoffset    = -12mm
\textwidth  = 163mm
\textheight = 225mm
\tolerance  = 600
\hfuzz      = 0.3mm

%
\newcommand{\pet}[1]{\underline{\bf #1}}
\newcommand{\Number}[1]{\ifnum#1<10\relax0\number#1\else\number#1\fi}
\newcommand{\isodate}{
\count151=\time
\divide\count151 by 60
\count151=\count151
\multiply\count151 by 60
\count152=\time
\advance\count152 by -\count151
\divide\count151 by 60
\count152=\count151
\multiply\count151 by 60
\count153=\time
\advance\count153 by -\count151
\Number{\year}.\Number{\month}.\Number{\day}--\Number{\count152}:\Number{\count153}
}

\pagestyle{fancy}
\rhead{Monitoring southern hemisphere \Fermi-detected AGNs}
\lhead{}
\rfoot{}
\lfoot{}


\title{\hm\vspace{-8ex} \LARGE\bf Monitoring southern hemisphere \Fermi-detected AGNs with
a Radio Interferometer in New Zealand}

%

\author{}
\date{}

\begin{document}

% abstract:
% 
%   We propose to run a program of monitoring all southern hemisphere Fermi associated active galactic nuclei brighter than 50 mJy at 8 GHz with a Radio Interferometer in New Zealand. We propose to observe 773 program sources with a cadence of ~15 days and determine their flux densities to within a accuracy of 5%. This program is complementary to the OVRO Blazar monitoring program and targets the 1/3 of the sky not covered by the OVRO program. There will be a 1/6 sky overlap between the two programs for consistency control. In addition, we reserve room for a further 50 sources that will be added to the observing list upon request. The light curves will be made publicly available immediately, typically within 15 days of observations.


\maketitle

\vspace{-12ex}

\vspace{-14ex}\hfill \framebox{\Large\bf Competition sensitive! Draft of \isodate }\vspace{12ex}

\section{Introduction}
  
   Analysis of \Fermi\ LAT data has revealed that more than one half of the 
detected point sources are active galactic nuclei (AGNs). An intrinsic 
property of AGNs is variability at scales from days to decades at all 
wavelengths from radio to hard $\gamma$-rays. One of the major outcomes 
of the \Fermi\ mission is monitoring of $\gamma$-ray loud AGNs. High 
energy light curves together with spectra in the MeV--GeV range and 
position localisation is the legacy data product of the mission. In order 
to enhance the outcome of the \Fermi\ mission, matching monitoring 
programs at other wavelengths are needed. The most comprehensive matching 
program is the ongoing OVRO 40-Meter Telescope Monitoring Program 
\citep{r:ovro} that has observed for 10 years a list of 1835~AGNs at 
declinations $>-20^\circ$, including 930~$\gamma$-ray associated sources 
from FL8Y~catalogue of point sources with a cadence of 2 times a month.

   The SED of AGNs has two distinctive broad peaks: one spanning from radio
through optical to soft X-ray and another spanning from KeV to TeV. 
The emission mechanism of these two peaks is different, monitoring in the 
radio does not therefore duplicate monitoring in the $\gamma$-ray range, 
but rather provides additional complementary information.

   Radio/$\gamma$-ray monitoring data are used for a statistical study of 
the AGN population and for case studies of selected sources. The focus of
the statistical studies is on deriving the radio and radio/$\gamma$-ray 
observational properties of the AGN population, including a) the radio 
variability properties of the AGN population, their dependence on redshift, 
spectral classification, luminosity, etc.; b) any differences between the 
radio properties of \Fermi\ detected AGNs and AGNs with similar radio 
luminosity which have not been detected by \Fermi; c) the properties of 
cross-correlations between radio and $\gamma$-ray flares. The focus of 
case studies is to derive the time delay between $\gamma$-ray and radio 
flares and detect periodicities and peculiarities in light curves.

   The OVRO blazar monitoring program is highly successful: by 2018 over 
one hundred peer-reviewed and proceedings papers used the light curves 
from that program. But geography sets the limit of the program: sources 
with declinations below $-20^\circ$, i.e. 1/3 of the sky are excluded.

\section{New observing capabilities in the southern hemisphere}

  The majority of radio telescopes are located in the northern hemisphere. 
The few existing southern hemisphere telescopes are heavily over-subscribed. 
To make things worse, budgeting restriction for the last 2--5 years has 
reduced the amount of time existing radio telescopes in the south are 
available to work on science programs, e.g. Parkes and Mopra. In this 
situation a large dedicated program on existing radio astronomical 
facilities is highly problematic.

  Our group has spent 2 years converting a former telecommunication 
30-m dish in Warkworth (latitude: $-36.4^\circ$, longitude: $174.7^\circ$), 
New Zealand, to a working radio telescope. 

  In 2014 the first successful results with a 6.7 GHz receiver were obtained 
\citep{r:wa15} and in August 2017 the first successful observations using 
an 8~GHz receiver were made. There is a smaller 12-m radio-telescope 
designed for geodesy also equipped with a 8~GHz receiver at a distance 
of 185.226 meter from the 30-m telescope. Since August 2017 both telescopes 
have participated in VLBI observations at X-band (8 GHz). Analysis of VLBI 
data on the 185m long baseline have shown excellent performance: residual 
phase delays over 24 hour period has a scatter of 5~ps, i.e. phase is stable 
with rms of $15^\circ$ and fringe amplitude is also stable.

  This prompts us to propose a program of using this former telecommunications 
dish (30-m) and the geodetic radio telescope (12-m) as a radio interferometer
suitable for source flux density monitoring. We have measured the sensitivity
of the interferometer and found that we can determine flux density of 
a~50~mJy source with the thermal noise of 5~mJy using an 8~minute integration 
time.

\section{Proposed work}

  We propose to run a program of monitoring \underline{\bf{all}}
\Fermi\ associated AGNs with declinations $< 0^\circ$ with flux densities 
brighter than 50~mJy at 8 GHz with this 185 meter baseline Radio Interferometer 
in New Zealand (RINZ). We have identified 773 such sources in the FL8Y 
catalogue. The target source list, available at 
{\sf http://astrgeo.org/radio\_fermi/rinz\_gi11\_targets.txt}, was attached 
to the proposal submission as a separate file. Each source will be observed 
with 1~to 8~minutes integration time as appropriate for its flux density. We 
plan to conduct two 24-hour observing sessions per week totalling 2500~hours 
per year. It will require four days to observe the entire list. Thus, our radio 
monitoring program will provide light curves with a cadence of 
$\sim\!\! 15$~days, close to that provided by the  OVRO monitoring program. 
We reserve room for $\sim\! 50$ more sources that will be added to the program
upon request, for instance, newly detected sources or flaring \Fermi\ sources. 
We intentionally set the overlap with the OVRO program in the declination range
of -$20^\circ$ to $0^\circ$. The purpose of this overlap is to check 
consistency of our results with respect to the OVRO monitoring results.

\section{Significance of the proposed work}

  The current OVRO monitoring program covers 2/3 of the sky. Our proposed 
program will cover the remaining 1/3 of the sky with an overlap of 1/6 with 
the OVRO program. Thus, the all sky $\gamma$-ray AGN monitoring mission will 
have a matching all sky OVRO+RINZ mission with no bright AGN left behind.

The merit of the hemisphere bias elimination is the following:

\par\vspace{-1ex}\par
\begin{itemize}\setlength{\itemsep}{-0.25ex}
   \item the risk of losing an important variable source just because 
         the existing monitoring program covers only a part of the 
         sky is eliminated.

   \item the number of sources for which time delay in radio/$\gamma$ 
         light curves is known will be increased by 50\%. Such sources
         are very valuable for case studies. \citet{r:ovro_delay}
         report 41 such sources. A number of papers were 
         devoted to analysis of light curves of such single 
         sources, for instance \citep{r:bha17}.

   \item southern radio sky in the time domain is mainly unexplored 
         territory. We expect interesting discoveries. 

   \item we expect our southern radio monitoring program will help
         to launch monitoring at optical wavelengths in the
         southern hemisphere creating a multiplication effect.
\end{itemize}

  One can argue that since 59\% of the Moon surface area is visible from the Earth, 
the opposite, invisible side is expected to look the same. The Luna--3 
mission demonstrated that this is not the case. Notably, a number of 
extraordinary \Fermi\ detections has happened in the southern hemisphere 
at declination $< -20^\circ$ and therefore they were not observable by 
OVRO. A few examples of remarkable events include:

\par\vspace{-1ex}\par
\begin{itemize}\setlength{\itemsep}{-0.25ex}
   \item the gamma-ray burst GRB 080916C ($\delta= -56^\circ38'$) in September 
         2008. This burst had ``the largest apparent energy release yet measured'';

   \item detection and localization a gamma-ray burst in the southern sky designated 
         as GRB 170817A ($\delta=  -23^\circ23'$) within 1.7~s of the gravitational
         wave signal; 

   \item  detection a weak gamma-ray burst starting 0.4 seconds after the LIGO event 
          GW150914 ($\delta= -22^\circ$) on September 2015. The odds of such an event 
          being the result of a coincidence or noise is evaluated at a level of 0.2\%.
\end{itemize}

  The event GRB 170817A was followed-up by the southern hemisphere telescopes,
however, no monitoring in radio spectrum was conducted for these southern sources 
before or during the corresponding remarkable events, except for the one which was 
identified with the IceCube neutrino detection. Luckily, concurrently with the most 
powerful (2~PeV energy) neutrino event HESE-35, dubbed `BigBird' registered on 
4 December 2012 with the IceCube neutrino detector in Antarctica, both \Fermi\ and 
the Long Baseline Array (consisting of radio telescopes in Australia, NZ and SA) 
monitored the corresponding area of the southern sky. Careful analysis of both 
\Fermi\ and radio observations allowed to identify the source of the 
ultra-energetic neutrino with the blazar PKS B1424--418 ($\delta = -41.8^\circ)$ 
with the probability of false positive 0.05 --- the first ever identification of 
the source of ultra-energetic neutrinos \citep{r:kad16}.

  The paper about the northern hemisphere program, \citep{r:ovro}, has 
collected 197 citations during the seven years after publication, and 91 peer 
reviewed papers are based on the light curves obtained by this program. This 
provides strong evidence that such a data product is indeed needed by the 
scientific community. Providing information about radio light curves of the 
1/3 of \Fermi-detected blazars not monitored by radio hitherto, their variability 
indices, epochs of flaring events, and their delay with respect to $\gamma$-ray 
flux will enhance the value of the \Fermi\ mission, especially that part related 
to the study of AGNs.

\section{Logistics of the proposed program}

  Observations will be performed in a sequence that minimizes slewing.
Integration time will be selected according to expected flux density
to have SNR $>$ 20 for weak sources and more than 30 for sources brighter than
100~mJy. The data will be recorded at 2 Gbps rate in dual-polarizations and 
transferred via ftp to the computer center of Auckland University of Technology 
for correlation. The data will then be correlated, fringe-fitted, and 
calibrated. The estimates of flux density, including all four Stokes 
parameters, will be made publicly available at the project web site 
immediately after completion of analysis, i.e. within 5--15 days after 
observations.

  Calibration will be performed by firing the noise diode of the antenna 
calibration unit before observation of every program source  
(a standard procedure in radio interferometry), by observing amplitude 
calibrator radio sources, and by observing common sources with the OVRO 
program. Our goal is to reach 5\% accuracy in calibration and a 5~mJy error 
floor. At the moment, only the 30-m radio telescope is equipped with the required 
antenna calibration unit. The second (12-m) radio telescope designed for geodesy
does not have it. The lack of the antenna calibration unit at the 2nd
antenna adversely affects accuracy of calibration, since antenna gain 
fluctuations at the 12-m antenna remain unchecked. Our analysis of VLBI
observations with the 12-m antenna provided us the estimate of accuracy of 
the antenna calibration without the noise diode at a level of 20\%. 

  Therefore, we request funds of \$30,343 to purchase an antenna 
calibration unit by the performing organization from the Haystack observatory, 
MIT that manufactures them. The performing organization will loan the unit to 
the Auckland University of Technology for the duration of this observing program. Using 
antenna calibration units at both antennas will reduce calibration errors 
from 20\% to 5\%, which is typical for radio interferometers. Calibration 
accuracy 5\% is required for scientific analysis of light curves. For 
comparison, the OVRO program has calibration errors at a level of 2--3\%.

Roles of the team members:

\par\vspace{-1ex}\par
\begin{itemize}\setlength{\itemsep}{-0.25ex}
   \item  L.~Petrov --- development of the pipeline of data analysis 
          and calibration; overall management of the project;
   \item  S.~Gulyaev --- data analysis, management of the Auckland University of Technology team;
   \item  S.~Weston, T.~Natusch --- tuning hardware, running the observations;
   \item  two Auckland University of Technology Master level students --- running the 
          observations, maintaining the project web site.
\end{itemize}

  We request funds at 0.1 FTE level for the PI, Leonid Petrov, for development
of the pipeline of data analysis. No funds are requested for foreign 
co-investigators. Their labor cost as well as the operational cost of running the 
interferometer is covered by Auckland University of Technology. The total amount of requested
funds is \$55,000.

  This monitoring program will be most valuable if performed concurrently 
with \Fermi\ observations. Since the ten year old \Fermi\ mission will not last 
forever, we need to start the observing program as soon as possible
while it remains operational. We intentionally set aside from the framework of this
proposal scientific interpretation of the monitoring results which we and other 
users of the RINZ AGN monitoring program will engage in. This important work can
be done later, but delaying the launch of the southern hemisphere monitoring 
program risks losing the time sensitive opportunity for concurrent \Fermi\ observations.

\section{Bibliography}

\begin{thebibliography}{8}\setlength{\itemsep}{0.25ex}

   \bibitem[Bhatta(2017)]{r:bha17}
      Bhatta~G., 2017. ApJ, 847: 7, 2017.

   \bibitem[Kadler(2016)]{r:kad16}
      Kadler et al., Nat. Phys, 12, 807--814, 2016.

   \bibitem[Max-Moerbeck et al.(2014)]{r:ovro_delay}
      Max-Moerbeck, W. et al., MNRAS, 445, 42,  2014. 

   \bibitem[Richards et al.(2011)]{r:ovro}
      Richards, J.~L.,  et al., ApJS, 194, 29, 2011.

   \bibitem[Richards et al.(2014)]{r:ovro+fermi}
      Richards, J.~L.,  et al., MNRAS, 438, 3058, 2014.

   \bibitem[Petrov et al.(2015)]{r:wa15}
      Petrov, L. at al.  PASP, 127, 516--522, 2015.

\end{thebibliography}

\end{document}

