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\begin{document} 
\section*{THE LIVING GALAXIES}

\vskip 0.8cm

{\Large{\bf A survey project with ODI at WIYN}}

\vskip 1.2cm

\section*{\bf Principal Investigators:}

\noindent {\bf Marina Orio, Rich Townsend} \\

\section*{Co-Investigators:}

\noindent {\bf Jay Gallagher, Daniel Harbeck, Sebastian Heinz} 
%
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\begin{center}
\includegraphics[width=4in]{m31_odi_var.ps}
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\newpage
%
\section{Abstract}

We propose temporal monitoring of the North-East quadrant of Andromeda
(M31), and all the Triangulum galaxy (M33), using the WIYN One Degree
Imager (ODI). These surveys will comprise the first systematic studies
of optical variability in the two galaxies that sample timescales
extending from minutes all the way through to years, and that
incorporate multiple filters including H$\alpha$. Within the
overarching theme of monitoring the `circadian rhythms' of our closest
spiral-galaxy neighbors, our science drivers are (i) to obtain a
comprehensive picture of compact-object binaries in outburst,
determining rates of different classes of novae and black hole
transients; (2) to derive statistics and basic parameters of quiescent
symbiotics and high mass X-ray binaries; (3) to establish whole-galaxy
censuses of variable massive stars ($\beta$ Cepheid pulsators and
disk-forming Be stars), allowing critical tests of stellar structure
and evolution. In addition to these three drivers, we will acquire a
superb database for the study of long-period variables, and moreover
obtain the deepest H$\alpha$ exposures ever obtained for M31 and M33.

%
\begin{figure}[h]
\begin{center}
\hbox{\psfig{figure=ODI1.ps,width=15.4cm}}
\end{center}
\vspace{ -1cm}
\caption{\small{Comparison between an HST ACS image, and the same
    image degraded to ODI best quality (middle) and best quality of
    the Mayall 4m telescope at Kitt Peak. }} \label{fig:spatial}
\end{figure}
%

\section{Motivation} \label{sec:motivation}

Throughout history, variable stars have led humans to pay attention to
``divine signs'' in the sky, and fostered people's curiosity about the
Universe. As we enter the second decade of the 21$^st$ Century, the
study of these variations as a \emph{survey} endeavor is now moving to
center stage. Out of 17 Letters of Intent that the IAU recently
received for symposia in 2011, two and large part of a third one are
completely dedicated to timing analysis of astronomical sources.  With
the outstanding image quality of WIYN, coupled with the wide field of
ODI, we propose to position UW-Madison at the very center of this
drive into the time domain, by undertaking the most comprehensive
temporal surveys ever of the closest spiral galaxies to our own galaxy
--- M31 and M33.

The name of the project --- \emph{The Living Galaxies} --- vividly
encapsulates what we hope to obtain from these surveys. Over the
multi-year duration of the project, we will be able to see the
galaxies as they've never been seen before --- not as frozen entities
which are to be studied at a single point in time, but as living
ecosystems which show energetic activity and variability across a
multitude of timescales. Of course, behind this rhetoric there are
solid scientific reasons for long-term, intensive monitoring of M31
and M31, which tie in closely with stellar astrophysics research
already undertaken at UW-Madison --- specifically, close binaries
undergoing mass transfer, and unstable massive stars. Efforts to
understand the fundamental physics governing these system, and to
explore the sensitivity to parameters such as metallicity, lie at the
forefront of modern astrophysics.

% By regularly monitoring rich and varied stellar population over one
% degree fields we will explore the parameter space of close binaries
% undergoing mass transfer, and of massive stars instabilities.  Massive
% stars and accreting binaries are two topics of excellence in
% Wisconsin, in which we have knowledge and expertise.  Transient,
% eruptive objects among these two classes of objects will constitute a
% main component of the {\it Living Galaxy}.  In addition, our database
% will be invaluable for microlensing studies, of interest to several
% international research groups and to one of our external
% collaborators. Our co-I Calchi-Novati is an expert of software used to
% identify variability in large datasets, and therefore brings also a
% precious contribution to the project.  We will also be able to measure
% the light curves of Cepheids and eclipsing binaries for accurate
% distance determinations and evaluation of the metallicity-standard
% candle relationship. Finally, since we will use H$\alpha$ images to
% pursue our scientific goals, we will obtain the deepest and most
% complete H$\alpha$ maps of these galaxies, which will be an important
% legacy of the {\it Living Galaxy}.

The classes of objects and phenomena we will study are described in
Section~\ref{sec:targets}. The observation plan is discussed in detail
in Section~\ref{sec:obs}, which includes a table indicating the
cadence and filters that are necessary for each of our scientific
goals.  In Section\ref{sec:previous} we briefly review previous
temporal studies of M31 and M33, and in Section~\ref{sec:odi} we make
the case for ODI being the ideal instrument for the project,
explaining why it is competitive in the realm of wide field
imagers. Section~\ref{sec:data} contains some plans on data analysis
and management, and in Section~\ref{sec:spec} we discuss plans for
spectroscopic follow-up to the project. Finally, we present the
project team at individual and institutional levels in
Section~\ref{sec:team}, and establish a provisional timeline in
Section~\ref{sec:time}.

%
\section{Science Targets} \label{sec:targets}
 
Our knowledge of the Local Group stellar populations has been greatly
expanded in recent years, thanks to high-resolution, wide-field
cameras on both ground-based telescopes and on the Hubble Space
Telescope (HST). The metallicity dependence of distance indicators
such as RR Lyrae and classical-Cepheid pulsators has been studied in
several galaxies, and Hertzsprung-Russell (HR) diagrams of extensive
regions of Local Group galaxies are revealing their intricate star
formation histories. ODI on WIYN, a one-degree-field detector with
scheduling flexibility and a substantial number of nights per year
allocated to the UW, will furnish an unprecedented opportunity to
further improve the study of interacting binary systems, a key element
in understanding the distant Universe.  Figure~\ref{fig:spatial} shows
the typical spatial resolution of ODI, compared with other ground
telescopes and with the HST. Although we cannot compete with HST, ODI
clearly stands above its ground-based peers, and is an excellent
choice for the study of resolved stellar population in nearby
galaxies.

Methods and software packages have been devised in recent years to
study variability for crowded and even non-resolved stellar
population. These will stand us in good stead when monitoring the
central 5 arcminutes of M31 and central 3 arcminutes of M33, where
crowding and diffuse light make other methods impossible.  However,
even at larger distances from the core, these rapid methods of image
comparison allow the discovery and characterization of variable
objects more quickly and efficiently than traditional photometry.

One of the most accurate determinations of the distance modulus of M31
is 24.47$\pm$0.06 (Stanek \& Granavich 1998).  This distance modulus,
comparable to that of M33, implies that we will observe a very large
number of optical transients in outburst, and moreover numerous
variable massive stars. In the course of this five-year project we
will obtain precise statistics on novae and symbiotic systems, explore
the behaviour of optical counterparts of eruptive of X-ray binaries
(XRB), especially those containing black holes, and learn about the
feedback of star formation on interacting binaries.

The white dwarf binaries data will have a significant impact in the
search for the progenitors of type Ia supernovae (SNe Ia). We will
assess the existence and frequency of other types of binary systems
harboring compact objects, and obtain an optical variability database
for a large number of other types of astrophysical object.  Our
project will overlap in time with \emph{Swift}, \emph{XMM-Newton} and
\emph{Chandra} monitoring of M31 and M33 in the UV and X-ray,
wavelength regions in which close binaries are very luminous.  The
UV/X-ray exposures will be available to us or to the community in
general, allowing us to derive several physically meaningful
parameters of these transient objects.  In addition, the recently
approved Multi-Cycle Treasury HST project on the North-East quadrant
of M31, the same region chosen by us, will yield superb reference
images at one epoch in several filters, including the UV.

Among periodically variable early-type (OBA) stars, the $\beta$ Cepheid
pulsators are the most luminous, but because of the high cadences
needed, they have not been studied well in external galaxies. The
instability strips in the upper HRD inhabited by these objects are
sensitive to stellar envelope opacities; thus, surveys of large
populations of $\beta$ Cepheids, at a variety of abundances, can be
used for stringent testing of laboratory measurements of opacity and
other microphysics.

Other early-type targets include Be stars, which episodically eject
equatorial material into a Keplerian decretion disk; and luminous blue
variables (LBVs), which show eruptive outbursts. The reasons behind
both of these irregular phenomena are still poorly understood, and
surveys of large populations of each are required to shine light on
possible avenues of future research.
 
\subsection{Accreting Systems} \label{ssec:targets-acc}

Close binaries undergoing mass transfer, especially white dwarf
binaries, are the area of expertise of PI Orio, who has been specially
involved with the search for candidate type Ia supernovae progenitors
in M31, mainly using X-ray observations (Orio 2006, Nelson et
al. 2009, Orio et al. 2010).  She is currently also involved in
spectroscopic classification of the M31 novae, in collaboration with
the Asiago and TNG telescopes of INAF (Di Mille et al. 2009; see the
numerous IAU Circulars and Astronomer's Telegrams by Di Mille et
al. in the reference list).  In conjunction with this program, and
with her X-ray monitoring of novae and supersoft X-ray sources in M31,
Orio has carried out observations of selected areas of M31 with WIYN
and the current mini-MO imager (Orio 2006, Orio et al. 2010), yielding
deeper and better photometric images (see Fig.~\ref{fig:lgs}) than the
Local Group Survey of Massey et al. (2006, 2007).

%
\begin{figure}[h]
\begin{center}
\hbox{
\psfig{figure=msseyha.ps,width=7.2cm}
\hskip 0.8cm
\psfig{figure=wiynha.ps,width=7.2cm}
}
\end{center}
\vspace{-1.cm}
\caption{\small{A detail from one of the mini-MO H$\alpha$ images, in
    a 0.8x0.95 arcminute area, is shown on the right while on the left we
    show the comparison with a public LGS image of the same
    region. The LGS image was obtained in a 5 minutes exposure at the
    4m Kitt Peak telescope.}} \label{fig:lgs}
\end{figure}

%
\begin{figure}[h]
\begin{center}
\hbox{ \psfig{figure=PTFnovae.ps,height=8.5cm,width=15cm}}
\end{center}
\vspace{ -1cm}
\caption{\small{The green squares are putative novae observed in
    external nearby galaxies by the FastTING team (courtesy of Shri
    Kulkarni and Mansi Kasliwal). The small green dots in the
    magnitude versus time for a 2 mag decay are the classical Galactic
    novae used to calibrate the Maximum magnitude Rate of Decay
    Relationship (MMRD). Recurrent Galactic novae, occurring on
    massive white dwarf, and SNe Ia candidate progenitors, are
    represented with the blue stars and they are not known to obey
    this relationship. Also shown is M31N07-11d, a RN of M31, and the
    location of the luminous red variables. It seems that the FastTING
    is observing mostly RN - this may be because of the frequent
    sampling that does allows not to miss RN. For this reason we plan
    observe M31 and M33 at least as once a week.}}
\end{figure} \label{fig:FastTING}


\begin{figure}[h]
\begin{center}
\hbox{
\psfig{figure=dec.ps,width=7.2cm}
\hskip 0.8cm
\psfig{figure=feb.ps,width=7.2cm}
}
\end{center}
\vspace{-1.cm}
\caption{\small {Chandra HRC-I images of the innermost center
    of M31 (1.5x1 arcminutes) taken on December 2 of 2004 and on February
    20 of 2005. The green circles show the X-ray (but also optical!)
    transients, observed to change every week, and usually identified
    as classical, recurrent and black-hole novae.}} \label{fig:chandra}
\end{figure}

Accreting systems can be studied in two states: in outburst and in
quiescence. In outburst we will primarily obtain the light curves of
novae and black-hole transients.

\subsubsection{Classical and Recurrent Novae (RN) in Outburst}

Extragalactic novae are the main tracers of interacting binary stars
in general, and also of the \emph{single degenerate} progenitors of
type Ia supernovae (SNe). Novae are also excellent indicators of the
star formation rate history of a galaxy: the outburst recurs more
often in systems containing high mass white dwarfs (WDs), so novae are
expected to be more often observed if there has been recent star
formation (Yungelson et al. 1997, Neill \& Shara 2004, 2005).

Recently, several efforts have been made to measure the nova rate of
M31, but they are based on small telescopes and small fields of view
(e.g. Darnley et al. 2006, Fliri et al. 2006, Heinze et al. 2008).
When normalized to the galaxy's luminosity, the most current estimate,
65 year$^{-1}$ (Darnley et al. 2006), appears to be much higher than
the equivalent measure for M33.
%The estimates
%for M33 vary between 2 and 5 year$^{-1}$ (Sharov 1993, Della Valle et
%al. 1994, Williams \& Shafter 2004)
This difference has been interpreted as an indication that novae are
mainly an old population, and seems to be confirmed by our study of
M31.  However, the differences in nova rates are the subject of
ongoing debate (e.g. Della Valle et al. 1992, Matteucci et al. 2003)
and the M31/M33 comparison is still based on small number statistics
for M33 (e.g. Williams \& Shafter, 2004) and small regions of the full
angular extent of M31.

Rather than continuing with the current practice of extrapolating the
nova rate of small fields to other regions of a galaxy (in spite of
differences in metallicity and star formation history), we will
measure precise rates over a very large portion our target
galaxies. With our 3.5m telescope, we will moreover be able to follow
the nova light curves almost to minimum, allowing classification of
the novae according to their light curve characteristics. Follow-up
spectral classification for many of the novae we discover, with WIYN
and the INAF Galileo telescope, will assist with this classification.

With these detailed diagnostics, we can eliminate the 15-20\% spurious
transients that might mimic novae (although these transients can be
interesting in their own right; see below). Then, we can establish the
incidence rates of the different types of novae --- a key step in
testing current theories. One of the first results from the FastTING
(Fast Transients in Nearest galaxies) survey is that there may be many
more T-Pyx type RNe (slow recurrent novae) than previously thought,
but they are missed in extragalactic surveys because they are not very
luminous at maximum (see Fig.~\ref{fig:FastTING}). This is an
interesting possibility that we will certainly be able to explore for
M31 and M33.

Although part of our scientific goals can be achieved without the $U$
and H$\alpha$ filters, these filters are very important for the
success of this project, especially H$\alpha$.  The UW Department of
Astronomy and the WIYN consortium have applied to US agencies to
obtain the filters as soon as possible.  Optical transients,
especially classical and RNe, are much brighter in H$\alpha$ than
other optical bands. We will use the broad-band filters instead of an
off-band filter to subtract the continuum level and resolve novae
spatially (even in most of the nucleus of M31 and M33) and obtain
precise positions (this is done routinely in extragalactic nova
searches). The $U$-band light curve is also of interest because both
the WD and the ejected shell emit in strongly UV (a fact known since
the early studies of Gallagher \& Starrfield 1976, 1977; see also Orio
et al. 2010 for results concerning specifically the novae in M31).

\subsubsection{Black-hole Transients}

Thanks to regular X-ray monitoring, several X-ray transients are
observed every year in M31 and M33.  About half are thought to host a
black hole. These systems display a simultaneous optical outburst, but
the eruption occurs without mass outflows and thus is very different
spectroscopically from classical/recurrent novae (e.g. Kuulkers,
1998). The instability that triggers the outbursts is thought to occur
in an advection-dominated accretion disk (e.g.  Meyer-Hofmeister \&
Meyer, 1999) and has very dramatic observational consequences,
reaching Eddington luminosity in X-rays and with a $\simeq$8
magnitudes amplitude (similar to RNe) at optical wavelengths.

In the past, black-hole binaries in eruption have often been mistaken
for novae, although the two can be clearly distinguished both in
X-rays (spectra and light curves are totally different for RNe), and
in optical spectra (there are no P-Cygni profiles in black holes). To
data, tens of candidate X-ray novae have been observed in M31 (e.g.,
Williams et al. 2005, and Fig.~\ref{fig:x-ray}), but without coeval
optical observations a confirmed identification is not possible.

\begin{figure*}
\begin{center}
\subfigure{\includegraphics[width=2.3in]{f3a.ps}}
\hskip 3cm
\subfigure{\includegraphics[width=2.3in]{f3b.ps}}
\caption{\small{Today stellar astronomy is also extragalactic.
    The X-ray light curves of two supersoft X-ray sources in M31 that
    show different periodicities in X-rays: r2-12 (left) of 217
    seconds, 18 minutes for Nova 2009 12-b (right). We show these
    results to demonstrate that variable stars in M31 can be more
    closely studied that we tend to think.}} \label{fig:x-ray}
\end{center}
\end{figure*}

An accurate rate and classification of black-hole transients in M31
and M33 is thus an interesting and important goal. In the core of M31,
where the black-hole transients are most often observed, we should be
able to use H$\alpha$ imaging as with classical and recurrent novae.
We are not able to reach HST resolutions in the innermost core, but
unlike HST, we can monitor the objects over months to obtain the whole
light curve. Optical light curves and spectra (obtained with
WIYN/Hydra or with the INFAF Galileo telescope) will differentiate
black-hole transients from novae. However, even in the absence of
spectra, multi-band light-curves will provide much of the needed
information.
%

\subsubsection{The Population of Quiescent X-Ray Binaries (XRB)}

About 2000 X-ray sources are known in M31, and 300 in M33.  Out of
1460 sources observed with XMM-Newton, about 300 have been found to be
variable (Pietsch et al., in X-Ray Astronomy 2009, in press). Some of
the M31 fields were only observed once, so the true number may be even
higher.  We estimate that with WIYN we can reach the optical magnitude
of more than 30\% of the quiescent XRB. This will offer a uniquely
large sample to test evolutionary models for XRB in general, and black
hole transients in particular. This research overlaps with co-I
Gallagher's involvement in studies of X-ray transients in E galaxies,
which can provide X-ray statistics but no optical identifications
(Brassington et al. 2008, 2009).

Together with this overall census, we plan to examine correlations
between X-ray and optical variability. Optical monitoring of all XRB
detected in M31 and M33 (low mass XRB in outburst, sometimes in
quiescence, and high mass XRB in quiescence) is extremely
interesting. We will be able to measure the orbital periods of more
than half of the known HMXB in our fields; by comparing them with the
Galactic and Magellanic Clouds populations of HMXB, we can investigate
the effect of metallicity on the formation and evolution of these
systems.

\subsubsection{Supersoft X-ray Sources}

Supersoft X-ray Sources (SSS) are defined phenomenologically as a class
of X-ray sources that include hot, accreting and hydrogen burning
white dwarfs in binaries. They are a major research focus for PI Orio.
SSS are extremely luminous (in the range 10$^{36-38}$ erg/s, thus
reaching the Eddington luminosity of a 1 M$_\odot$ star), but the
emission peaks in the very soft X-rays or extreme UV, and therefore
often suffers strong strong absorption. For this reason, the bulk of
SSS are observed in external, nearby galaxies (including and even
beyond the Local Group; see Fig.~\ref{fig:sss}) in directions of low
N(H). SSS often exhibit extreme behavior, such as X-ray flux
variability on time scales of minutes or hours (orbital, white dwarf
spin and probably non-radial pulsations). We know that about 50\% of
SSS are post-outburst novae and recurrent novae, and 20\% to 35\% turn
out to be other types of accreting and shell hydrogen burning white
dwarfs in binaries (see Greiner 2000, Orio 2006 and Fig. 5, from Orio
et al. 2010).

Both the frequently erupting RNe and the non-novae SSS are very
interesting as type Ia SN progenitors. M31 is regularly monitored in
X-rays over large fields\footnote{PI Orio is a co-I in some of the
  X-ray monitoring programs of M31 and M33, which are likely to be
  continued by the Chandra and XMM-Newton observatories into the ODI
  era.}, leading to the discovery of tens of SSS every year. These
observations lack the accompanying optical light curves necessary to
interpret the mechanism behind the X-ray variability. However, with a
large fraction of SSS having optical counterparts that are
sufficiently bright to be observable with WIYN, this gap can be closed
by the \emph{Living Galaxies} survey --- allowing us for instance to
understand whether thermonuclear burning in accreting WDs proceeds at
a constant rate, meaning that the system is on a path towards a SN Ia.
%The SSS
%that were re-observed in X-rays turned out to be persistent, transient
%or recurrent X-ray sources.

% Making use of X-ray, UV and optical images, in Nelson's 2009 PhD hesis
% at the UW we found that SSS either associated with old populations, or
% with star forming regions and OB optical counterparts. The latter are
% possibly Be+white dwarf systems, and in fact a classification as high
% mass XRB (HMXB) has been suggested by us (Orio et al. 2010, yellow and
% orange stripes in the Fig. 5 histogram).  If we can prove that they
% are HMXB, they would explain the time dependent, star formation
% dependent component in the type Ia SNe rate.  We do need optical
% lightcurves for a more complete characterization.
 
\begin{figure}[h]
\begin{center}
\includegraphics[width=3in]{f1Nb.ps}
\vspace{-1.cm}
\caption{\small{The distribution of SSS in M31 (Orio et
    al. 2010, submitted to ApJ) in different groups: classical and
    recurrent novae after an optical outburst, supernova remnants,
    AGN, still unclassified objects observed multiple times, or
    observed only once.  The unidentified SSS are either associated
    with old populations, or with star forming regions and OB optical
    counterparts (yellow and orange stripe).  The sources that were
    re-observed in X-rays turned out to be persistent (few), transient
    or recurrent (most).}} \label{fig:sss}
\end{center}
\end{figure}
% 
    
\subsubsection{Symbiotics}

In symbiotic binary systems a cool star (a red giant) has a hot
companion (usually a compact object, mainly a white dwarf), often
surrounded by a nebula. When there is a WD, shell H burning often
occurs. As mentioned above, there is an overlap between symbiotics and
SSS. There is also an overlap between symbiotics and recurrent novae,
since symbiotics at times undergo thermonuclear flashes. The compact
object accretes material through a wind or even an accretion
disk. Some symbiotics are likely progenitors for type-Ia SNe (Hachisu
et al., 2008).  The statistics, and when possible, determination of
the physical parameters of a symbiotics will place constrains on the
evolution of these systems and make progress in the study of type-Ia
SN progenitors. No symbiotics have been observed and studied yet in
M31 and M33, although the discovery of a symbiotic in IC 10 at a
$\simeq$700 kpc distance (Fig.~\ref{fig:symb}) demonstrates the
feasibility of finding extragalactic symbiotics with H$\alpha$ imaging
and spectroscopic follow-up with a mid-size telescope. We will monitor
and measure the orbital periods of these systems, and we may even
witness some outbursts and obtain indications of other variable
outflows.
%
\begin{figure}[h]
\begin{center}
\includegraphics[width=4in]{ICsymbio.ps}
\caption{\small{The optical spectrum of the symbiotic star
    StSy-1 in IC 10, a dwarf irregular and starburst satellite of M31,
    taken with two gratings and the CMOS-N detector at Gemini North,
    and comparison with the observed spectrum of the Galactic
    symbiotic Hen 2-147. See Goncalves et al. (2008) for details.}
} \label{fig:symb}
\end{center}
\end{figure}

\subsection{Massive Stars}

Massive stars are \emph{galactic feedback engines} --- via their
strong winds and supernova explosions, they inject huge amounts of
energy, momentum and material into their surrounding environments,
driving the chemical evolution and star formation of their host
galaxies. Throughout their lives, they also weather a host of
instabilities that can drive periodic pulsations (e.g., the $\beta$
Cepheid stars and slowly pulsating B stars), trigger the episodic
ejection of equatorial material into a Keplerian disk (e.g.,
Be stars), and produce eruptive episodes that drive off significant
amounts of mass (e.g., Luminous Blue Variables). These instabilities
are intricately linked with the physical processes occurring deep
within these stars' envelopes, and thus can potentially shed light on
aspects of stellar astrophysics that remain poorly understood.

\subsubsection{Be Stars}

Be stars are early B-type stars characterized by the appearance
(transient or continuous) of H$\alpha$ emission, presumed to come from
an equatorial \emph{decretion} disk. The mechanism for the formation
of this disk remains one of the longest-standing mysteries of stellar
astrophysics; rotation, pulsational instabilities and even magnetic
fields may each play a role. In recent years, with the emergence of
evidence that Be stars may rotate very close to critical (see Townsend
et al, 2004), there has been a groundswell of interest in these
objects as laboratories for understanding the structural and
evolutionary effects of extreme rotation.

Unfortunately, 25-50\% of Be stars go unobserved in optical surveys,
because their disks are not permanent and have very variable structure
(McSwain et al. 2008, 2009). Hubert \& Floquet (1998) examined the
Hipparcos sample of Be stars and found that early-type Be exhibit a
very high degree of variability. They also identified 14 Be stars with
recurrent short-lived outbursts (0.06$\leq \Delta \mathrm{mag},\leq$
0.3 over timescales of 50-500 days) and 8 with long-lived outbursts
($\Delta$mag $\geq$ 0.12 over timescales of $>$500 days) in the
sample.
%The H$\alpha$ band is better suited to measuring variations
%in the disks of Be stars of all spectral types.  
McSwain et al. (2008) discovered a new Be star (\#130) in the open
cluster NGC 3766 whose H$\alpha$ line switched from emission to
absorption over a couple of years, indicating the rapid dissipation of
its disk.

The \emph{Living Galaxies} survey will allow a representative census
of the Be-star populations of M31 and M33, determining the overall
incidence rate of the Be phenomenon (and how this might vary with the
strong metallicity gradients in M33), and establishing disk formation
and destruction timescales. The former will shed light on why the
phenomenon manifests itself in some stars and not others; and the
latter will help us constrain the physical processes that build and
then destroy the stars' circumstellar disks.

%
\begin{figure}[h]
\begin{center}
\includegraphics[width=4in]{instability-strips.ps}
\caption{Pulsation instability strips in the upper main sequence, computed using OPAL opacities. From Pamyatnykh (1999).} \label{fig:instab}
\end{center}
\end{figure}
%

%
\begin{figure}[h]
\begin{center}
\includegraphics[width=4in]{v838.ps}
\caption{The HST-ACS image of the light echo of V838 Mon, at a distance
 of about 10 kpc. We know only one such object in M31...
 how many more of them wait to be discovered?} \label{fig:v838}
\end{center}
\end{figure}
%

\subsubsection{$\beta$ Cepheids}

$\beta$ Cephei stars are massive ($M \gtrsim 8\,M_{\odot}$) main-sequence
stars showing periodic light and spectroscopic variations, with
typical periods of a few hours and amplitudes up to 0.3 mag. The
variability arises from self-excited radial and non-radial pulsations,
driven by a $\kappa$-mechanism instability operating on a peak in the
stellar envelope opacity at temperatures $\sim 200,000\,{\rm K}$. This
peak --- often termed the `iron bump' --- arises due to millions of
bound-bound transitions of iron and nickel. Fig.~\ref{fig:instab} shows
the regions in the upper part of the HRD inhabited by iron-bump
pulsators --- both $\beta$ Cephei stars and, at lower luminosities ---
slowly pulsating B (SPB) stars. The boundaries of these instability
strips are strongly sensitive to metallicity, and therefore surveys of
pulsating massive stars are ideal tools for probing abundance
distributions and/or testing opacity data.

Extragalactic surveys have so far extended only to the Magellanic
Clouds (Sterken \& Jerzykiewics, 1988, Pigulski \& Kolaczkowski,
2002), because of the high cadences required, and the need for
spectroscopic follow-up to weed out objects that mimic $\beta$ Cepheid
behavior. With the \emph{Living Galaxies} survey, we will be able to
find almost all high-amplitude ($\Delta m \gtrsim 0.1$) $\beta$
Cepheids, providing us with the first near-complete censuses of these
massive pulsators in regular galaxies.

\subsubsection{``V838 Mon''-type Objects}

Beautiful HST images illustrate the optical echo of V838 Mon (see
Fig.~\ref{fig:v838}), but the nature of this object is really still
elusive. Almost certainly this phenomenon is an eruptive stage in
advanced high mass binary stellar evolution, but it is still a matter
of intense debate and study.  A similar eruption was already observed
once in M31 (see Bond \& Siegel 2006 and references therein). Many
peculiar variables of this type are probably mistaken for classical
novae, because of infrequent monitoring and lack of identified
quiescent counterparts, but by closely following the light curves of
many variables M31 and M33, since the light curve really is very
different in novae and in V838 Mon type variables, we will select
candidate optical transients of this type and find out whether they
have a binary star with a massive component as quiescent counterpart.

\subsection{Companion Projects}

\subsubsection{Microlensing Studies}

Since the original suggestion by Paczynski (1986), microlensing is an
established research tool for the detection of compact halo object
(MACHOs), a possible dark matter component of galactic halos.  Several
microlensing campaigns have been undertaken in the last 20 years
towards the Galactic centre and the Magellanic Clouds (e.g. Moniez,
2010) and towards M31 (e.g. Calchi Novati, 2010).  In particular,
towards M31, observational campaigns have been carried out by several
collaborations, among which are AGAPE and follow-ups (Ansari et al
1999, Calchi Novati et al.  2005, 2009), WeCAPP (Riffeser et al 2006,
2008), MEGA (de Jong 2006).  In addition to offering a database for
M31, our survey will be a \emph{unique} resource for microlensing
studies in M33.  These surveys were carried out with smaller
telescopes and field of views than WIYN with ODI. Incidentally, they
are useful for our variability study because they offer a long term
basis to compare a number of our variables. However, as for the MACHO
surveys, all the microlensing results are still controversial. Our
survey should offer new, high quality material for these studies. co-I
Calchi Novati is PI of the PLAN collaboration, and is enthusiastic at
the idea of becoming our link to ensure that our database is exploited
properly for microlensing searches.

\subsubsection{Classical Cepheids} 

There have been recent attempts to better determine the distance to
M31 and M33 through the period-luminosity relation of classical
Cepheid pulsators (Vilardell et al. 2008), but the dependence of the
stars' light curves on metallicity still needs improvement. This is of
course a fundamental problem in astronomy, and one to which our data
will contribute essential information.

\subsubsection{Eclipsing Binaries} 

We will obtain excellent light curves for the most luminous eclipsing
binaries of M31 and M33, to be used to refine distance determinations
(e.g. Todd et al. 2005, Vilardell et al. 2006). Since this will be
carried out with the same data sets used for the Cepheids, it will
allow an accurate inter-comparison of the derived distances without
the uncertainties associated with photometric calibrations.

\subsubsection{Deep H$\alpha$ Imaging}

Figure~\ref{fig:m31-halpha} shows a beautiful image of one of the M31
fields, obtained by co-I Gallagher with WIYN and
Mini-MO. Figure~\ref{fig:lgs} illustrates the comparison with 4m NOAO
telescope and the LGS. Although the \emph{Living Galaxies} survey has
many components that can be done with broad band filters, H$\alpha$ is
the most interesting in many respects. It will be essential for a
quick and precise recognition of recurrent and classical novae and it
will allow to map virtually all symbiotics in the rich population of
Andromeda and the Triangulum.  Wide field deep images in this filter
also open up a series of possibilities that go beyond our original
goals.
%
\begin{figure}[h]
\begin{center}
\hbox{\psfig{figure=jay1-h.ps,width=7.7cm}
\hskip 0.1cm
\psfig{figure=jay1-R.ps,width=7.7cm}}
\end{center}
\vspace{ -1cm}
\caption{\small{A field of M31 imaged in H$\alpha$ by Gallagher with
    the WIYN Mini-Mosaic in a 15 minutes exposure.  The H$\alpha$
    image after subtraction of the normalized R image is shown on the
    left, and the original R image is on the right.  The R-image
    subtraction procedure allows faint structures to be resolved in
    detail.}} \label{fig:m31-halpha}
\end{figure}
%

\bigskip

\begin{table}[t]
 \[
 \begin{array}{|c|c|c|c|c|} \hline
$Class of sources$ &  $Time scales$  & $Cadence$ &  $Variation amplitude$        & $Filters$ \\
\hline
                   &                 &           &                               &                   \\
$Classical novae$  & 1 $ year$           & $weekly$  & 8-17 $ mag (steady decrease)$   & g, r, i, $H$\alpha \\
                   &                     & $monthly$ &                              &    $U$            \\
                   &                     &           &                              &                 \\
$Recurrent novae$  & 2-9$ months$        & $weekly$  & 8 $ mag (steady decrease)$      & g, r, i, $H$\alpha \\
                   &                     & $monthly$ &                                &  $U$                 \\
                   &                     &           &                                &                    \\
$Symbiotics$       &  <6 $ months$       & $weekly$  & 8-10 $ mag$                     &  g, r, i, $H$\alpha \\
$(in outburst)$    &                     & $monthly$ &                                &  $U$                  \\
$Symbiotics$       & 1-5 $ years$         & $monthly$ & 0.1 $ mag (oscillation)$        & g, r, i \\
$(quiescent)$      &                     &           & \geq 0.1 $ mag (orbital)$       & r, i     \\                                    &                     &           &                                &      \\
$SSS (bright phases)$ & 1-3 $ months$     & $weekly$  & \geq 0.05 $(irregular)$        & g, $U, H$\alpha \\                               &                   &           &                                &      \\
$Microquasars$     & 2-8 $ months$        & $weekly$  & 7-8 $ mag$                     & g, r, i, $H$\alpha \\
                   &                     &           &                               &         \\
 \beta $ Cepheids$  & 2-17 $ hours$        & $daily for$ >4 $ hours$ & \geq 0.1 $mag (pulsation)$ & g, r, i \\
                   &                     &           &                               &         \\
$Microlenses$      & 1-21 $ days$         & $daily$   & \geq 0.05 $(oscillation)$    & g, r \\
                   &                     &           &                               &      \\
$LPV$              & > 80 $ days$         & $bi-monthly$ & \geq 2.5 $(orbital)$       & g, r, i \\
$LPV (blue)$       & $ few days$          & $daily$   & \geq 0.05 $(orbital)$         & g, i \\
                   &                     &           &                             &          \\
$Be stars$        &  > 50 $ days$        & $monthly$ & \geq 0.05                   & g, r, $H$\alpha \\
                   & > 500 $ days$        & $bi-monthly$  & \geq 0.12               & g, r, $H$\alpha \\
                   &                     &           &                             &                     \\
$HMXB$             & 1-3 $ years$         & $monthly$ &  \geq 0.1 $ mag (orbital)$ &  g, $U$    \\
                   &                   &         &                          &      \\
$Cepheids$         & 5-200$ days$      & $once$/2 $days$ & \geq 0.2 $ mag (pulsation)$ & g, i \\
                 &                   &             &                         &      \\
\hline
         \end{array}
   \]
   \caption{Types of variability of the major classes of variable systems and events we will observe,
     variability timescales and useful filters} \label{tab:classes}
\end{table}

\section{Observing Plan} \label{sec:obs}

The characteristic variability timescales of our targets extend over
two or more orders of magnitude (see Table~\ref{tab:classes}; thus,
the observational cadence must be chosen carefully in order to ensure
that all relevant timescales are adequately sampled. We plan to
achieve this by beginning with a short cadence ($\lesssim$ hours), and
then progressively lengthening the cadence as the survey
progresses. This addresses the sampling issue, and at the same time
allows the project to be scientifically productive from the very start
(since data for the shortest-timescale objects, e.g. $\beta$
Cepheids, will be available within the first week).

A significant constraint on the observational planning is that it must
fit within the telescope scheduling. UW-Madison will have at most five
consecutive nights when M31 and M33 are at low airmass.  Around this
time of the year ({\bf when?}) the weather can be very variable, and
seeing is also not excellent for the whole night.  Our plan is
therefore to observe M31 and M33 all night for 2--3 consecutive
nights, and then follow on with 5--8 \emph{half} nights during the
period of longer visibility of the galaxies.  The half nights must be
scheduled as consecutively, or closely spaced, as possible. During the
rest of the year, our analysis of Table~\ref{tab:classes}) indicates
that about 1--2 hours of observing time per week would be optimal.  We
expected a S/N=10 for 23$^{\rm rd}$ mag with an exposure time of ..
in ... filters respectively.

In planning total exposure times, we must account for the length of
the H$\alpha$ observations, with an exposure time of about 15 minutes.
Because of the many gaps in the ODI camera, the optimal strategy is to
dither each exposure with 8 short sub-images. The decision on how
often to dither will be made once the characteristics of the
instrument are better known. At the moment the overhead time is not
exactly known, but with 8 sub-images per exposure, the total overhead
can be expensive and has to be accounted for, to achieve the best
possible planning. We know that we will need about 30 seconds for
acquisition, and \emph{possibly} a minute of total time for each move,
depending on some characteristics of the electronics, reaching a total
8 minutes of overhead time for each set of dithered observation.

With the dithering and overheads, the short (1-5 minutes) broad band
exposure will be relatively time consuming and need to be planned
accurately, possibly ruling out the dithering for part of the
nights. Our co-I Daniel Harbeck at WIYN is the ODI Project Scientist,
and with him we will refine the strategy to adopt during the
verification phase of the instrument.

We are currently exploring contingency plans to maximize the science
in case of missed observations due to weather and technical
problems. The other significant outstanding question concerns the mode
in which the observations will be undertaken. At this time there is no
general users' queue set up for ODI. During the UW-Madison nights, we
will be able to share time with the ODISSE survey (PI Barger), and
with other observers. However, UW may benefit from buying time from
the Yale University's survey queue. Another possibility we are
investigating is remote observing, already set up from Wisconsin for
other WIYN instruments.
  
\emph{Weekly monitoring, whenever possible, in at least two filters
  for $\simeq$7 months a year is an essential component of our
  project, a winning strategy for many goals}.  The two filters are
necessary to distinguish source classes. Fig.~\ref{fig:FastTING}
indicates that a weekly cadence is necessary to detect the novae,
recurrent novae and other transients that are the most interesting to
us: high mass white dwarfs, possibly on the path to SNe Ia explosions
(the amplitude and speed class of the thermonuclear outburst is
inversely proportional to the mass) and of course black-hole
transients. \emph{Thus, for the success of this project a strategy
  should be in place for some mode of queue or remote observing that
  allows repeating short observations for many nights during the
  year}.

\section{Previous Surveys of M31 and M33} \label{sec:previous}
 
Both M31 and M33 have been surveyed photometrically with great
precision in the Local Group Survey (Massey et al. 2006). The M31
population has been also measured in the Sloan Survey. We will thus
have a fixed epoch reference obtained a few years before the
\emph{Living Galaxies} survey, and we will be able to judge the
quality of our photometry and improve it, when and if necessary.

An additionally external project relevant to us is the large
Panchromatic Survey of M31 planned as an HST Treasury project.  In the
area covered by HST, the spatial resolution and the quality of the HST
images will be invaluable for the variability study of our WIYN
exposures, because they will give us a high resolution template for
deconvolving WIYN images when variable targets are situated in crowded
regions.

The HST Panchromatic Survey includes ultraviolet filters. The
ultraviolet images of this survey, when they become public, will allow
quick identification and astrometry of variable sources when the field
is too crowded to identify the correct optical counterpart of SSS and
some other types of XRB, or when the source is too faint for detection
with other filters. Once we know the existence of a counterpart that
we think will likely show orbital variability, a method like pixel
imaging with ODI will give the necessary information with optical
filters.

\section{ODI Amongst its Peers} \label{sec:odi}

Although wide-field cameras are becoming increasingly common on
intermediate- and large-size telescope, ODI at WIYN has unique
strengths that set it apart from its competitors. In the Northern
hemisphere, the most comparable facility is the 3.6m
Canada-France-Hawaii Telescope (CFHT) with the MegaCAM
imager. However, their best angular resolution is poorer than ours,
and their field-of-view in H$\alpha$, covering 42x28 arcminutes$^2$,
is substantially less than the full one square degree. Moreover, being
a multinational-level facility and supporting a wide array of popular
instruments, the opportunities to undertake high-cadence surveys with
CFHT/MegaCam are quite limited.

The Palomar Transient Factory (PTF) --- the 1.2m Palomar telescope
with an 8 square degree imager, supported by the 1.5m telescope for
some light curve measurement (Law et al. 2009) --- is better suited
than ODI at finding transients across the full sky. However, it is a
poor choice for intensive monitoring of individual clusters or
galaxies; it cannot resolve transients anywhere near galactic centers,
and does not use H$\alpha$ filters. Nevertheless, we aim to
collaborate with the PTF team in optimizing our observational plan
(\S\ref{sec:obs}).

Looking now to the future, the 8m Subaru telescope will soon be
equipped with Hyper-Suprime Cam, a one degree imager ({\bf check})
which \emph{will} have an H$\alpha$ filter; however, this facility is
dedicated mostly to distant objects and cosmology, and is not expected
to be a monitoring survey instrument.

The Pan-STARRS survey, employing (ultimately) four 1.8m telescopes
equipped with the same Orthogonal Transfer Array (OTA) CCDs used by
ODI, will be dedicated to studies of optical transients and
variability in external galaxies. No plans exist for use of an
H$\alpha$ filter, and at present the limiting magnitude (for given S/N
and length of exposure) is 1.5 mag shallower than that that achievable
with WIYN. Moreover, it seems unlikely that Pan-STARRS can achieve an
image quality of $\leq$0.8 arcseconds.

In the Southern hemisphere the Large Synoptic Survey Telescope (LSST),
scheduled for completion in 2016--2017, will be much more effective
than WIYN in terms of etendue (FOV x collecting area area).  The
information that will be obtained by LSST on the variable stars of the
Magellanic Clouds and other nearby galaxies' populations (e.g. IC 101,
NGC 6822) will be an invaluable comparison to the Northern-hemisphere
data from the \emph{Living Galaxies} survey.

\section{Data Management and Analysis} \label{sec:data}

After the pipeline reduction provided by the University of Indiana ODI
data center, the initial analysis of the \emph{Living Galaxies} images
will be undertaken by a post-doctoral collaborator (to be recruited,
possibly in common with the ODISSE project). Co-I Calchi Novati will
provide guidance here, having significant past experience with
microlensing projects and, specifically, \emph{Pixel Imaging
  Software}. Another type of package we may want to use is
\emph{Difference Image Analysis} (DIA) software.  Both types of
software allow detection of variability at low levels, even in
non-resolved images (e.g. the inner $5''$ from the center of M31, and
about $3''$ from the center of M33, regions that appear flooded with
diffuse light in the WIYN exposures).  Given the copyright/licensing
restrictions of the microlensing software, we plan to train the
post-doc to analyze all the images as they are obtained. This will
allow us to detect and locate variability as well as measure accurate
photometry in ``stamp like'' sub images around the variables. Only in
the most crowded core areas of a few arcminutes will accurate
photometry not be possible; however, some spatial information, and the
possibility of measurements, will remain in our H$\alpha$ images.

Full photometric pipelines will be established later in the project,
to set up a \emph{Living Galaxies} archive for posterity. We have made
initial contact with a colleague ({\bf who?}) at Padova who has worked
with the Terapix collaboration, and are already exploring optimal ways
the archiving can be achieved. The Terapix group provides imaging and
pipeline processing software to the CFHT MegaCAM and their (available)
WiFIX software is of course of interest for ODI.

\section {Spectroscopic Follow-up} \label{sec:spec}

Spectroscopic identification and follow-up will be an important part
of the \emph{Living Galaxies} survey, especially for transients and
for the identification of new symbiotics (see Fig.~\ref{fig:symb}.
The Hydra spectrograph of WIYN will be available to us, making a large
part of this project self-sufficient without relying heavily on
external facilities. In addition we will apply for time on the
Padova-Asiago 1.2m and 1.8m telescopes and on the TNG-INAF 3.5m
telescope and the SARG spectrograph. The INAF Galileo telescope is
very similar and yet very complementary to WIYN --- with a smaller
field of view, it offers a high-efficiency spectrograph. The novae in
M31 during outburst are in the $V$=15--18 range, and TNG can follow
them spectroscopically during the early weeks/months of the decline.
We intend to develop a collaborative spectral follow-up program and
make it part of the \emph{Living Galaxies} survey; in this respect,
our co-Is from Padova are leading experts in spectroscopy of novae and also
of symbiotics, and are already engaged in a spectroscopic survey of
M31/M33 novae.

Spectral are critical for assessing the physical nature of transients.
For example, Di Mille et al. (2010a, 2010b) have already been able to
weed out a spurious object (a WZ Sge variable in the M31 foreground)
using their first collection of nova spectra.  Much of the
spectroscopic nova project is based on the behavior of Galactic and
LMC novae described by Williams (1992).  Williams classified novae
near visual maximum in two spectroscopic classes, determined by the
relative strength of the non Balmer lines of Fe II, He, and N.  Novae
with FeII lines show a lower level of ionization and P Cygni profiles.
Novae with strong He/N lines show a higher level of ionization and the
lines are mostly flat-topped. Following this classification, Della
Valle \& Livio (1998) found that He/N novae tend to concentrate close
to the Galactic plane and are fast and bright, while Fe II novae are
slow and faint and are distributed up to $z \sim 1000$ pc and beyond.
No RNe have been observed to belong to the Fe II class.  Recently Di
Mille et al. (2010) used spectra in the literature and new
observations obtained at Asiago and at TNG (Fig. 10, 11) to analyse
the spatial distribution of the different classes of objects in M31 .
Their results do not show a striking difference between the
distribution of He/N an FeII novae but they stressed that to correctly
weight statistical biases a complete spectroscopic classification of a
much larger number of the M31 and M33 novae is very important to
constrain the theory.

\begin{figure}[!ht]
\includegraphics[width=10 cm]{nm31-2008-10b_26102008.fits.eps}
\caption{TNG spectra of nova NM31-2008-10b at different epochs}
\end{figure}
%
\begin{figure}[!hb]
\caption{NM31 2007-11c spectra at Asiago Observatory}
\includegraphics[width=10 cm]{s1.0001.fits.eps}
% s1.0001.fits.eps: 577x577 pixel, 72dpi, 20.36x20.36 cm, bb=
\label{fig:2007-11c}
\end{figure}

\section{Project Team} \label{sec:team}

In addition to co-PI Townsend, our co-Is among faculty members at
Wisconsin are Professors Jay Gallagher (stellar populations and
galaxies) and Sebastian Heinz (black holes and compact objects in
general). A co-I in the project is Dr. Daniel Harbeck, ODI Project
Scientist. Dr. Patricia Knezek has expressed interest.  Several other
INAF colleagues of Orio are interested in collaborating with the
\emph{Living Galaxies} survey in their areas of expertise.

We already have several Italian collaborators associated with the the
Italian Institute of Astrophysics (INAF): Drs. Iijima and Siviero
(INAF Padova), Dr. Calchi Novati (Salerno University), Dr. Di Mille
(Magellan Telescope and Padova University), Profs.  Bianchini, Ciroi,
and Rafanelli (Padova University).  Letters of interest have also been
received from Dr. Ginevra Trinchieri (INAF-Milano, XRB populations in
external galaxies), Dr. Domitilla de Martino and Dr. Massimo Della
Valle (INAF-Napoli, cataclysmic variables, novae outbursts, black hole
candidates), and Drs. Ulisse Munari (INAF-Padova, symbiotic stars and
novae). The research team of Prof. Scarpetta, with which Calchi Novati
works in Salerno, has expressed interested in in studying the
microlensing events in our exposures, on behalf of the PLAN
microlensing international collaboration.  In parallel we expect also
to have collaborators from the massive stars and Be-star communities,
and we will develop these links once the timeline and ODI capacities
become clearer.
 
\section{Timeline} \label{sec:time}

During the science verification phase of ODI we will analyse technical
and organizational problems that are difficult to solve before having
access to the data in their final format.  We still cannot gauge exact
overhead times, which may be as short as the 30s acquisition time if
the telescope can move without significant electronic noise, or almost
twice as long. This will have impact on how many dithered images we
decide to obtain.  We will also learn how to use the variability
software on the ODI images and continue the collaboration with the
Padova Astronomy Department on the M31 and M33 nova spectra, already
before many new novae are discovered by ODI, as a scientific
foundation for interpreting results from the nova database we will
acquire.

{\bf The following is unedited, and needs tidying up....}

As soon as ODI is fully operational we plan to analyse the data to
obtain rates of novae, recurrent novae and transients with black hole
candidates. After the first year we would like to publish some ``early
science'': rates of these three types of events, especially the nova
rate, with a spectroscopic library of support for classification.
 
One of our first goals is also to identify symbiotics for the first
time in M31 and M33, which can be spectroscopically distinguished from
planetary nebulae, and obtain a picture of the M31 and M33 symbiotics
population, which then we can compare with the type Ia supernova rate.

We plan this survey as a five years project. Three years is the
minimum length of time we think we need to achieve completeness in
some areas of this research, such as the study of transient Be stars,
and microlensing candidates, which must be distinguished from the
other eruptive variables.

Initial requests of funding for a preliminary phase of accurate
preparation have been submitted to NSF in the context of a general
proposal on X-ray binaries, and to INAF on the side of the Italian
collaboration. We are aware that the \emph{Living Galaxies} survey
will require the dedicated work of a post-doctoral scientist, and hope
to obtain some funding to hire such a precious collaborator.
 
We would like to stress that early acquisition of an H$\alpha$ filter,
and definition of a queue or remote observing mode to obtain weekly
monitoring observations, are essential for the success of the project.
 
\section{References}

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