\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}