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\begin{document}

\title{
HST FUV Observations of Brightest Cluster Galaxies: The Role of Star Formation 
in Cooling Flows and BCG Evolution
}
\author{Kieran O'Dea, Alice C. Quillen}
\affil{Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627, USA} 
\author{Bradford Snios, Grant Tremblay, Chris P. O'Dea, Stefi A. Baum,
Kevin Christiansen} 
\affil{Department of Physics, Rochester Institute of Technology,
  84 Lomb Memorial Drive, Rochester, NY 14623-5603, USA} 
\author{Megan Donahue, Mark Voit} 
\affil{Michigan State University, Physics and Astronomy Dept., East Lansing, MI 48824-2320, USA} 
\author{\& Alastair C. Edge}  
\affil{Institute for Computational Cosmology, Department of Physics,
  Durham University, Durham DH1 3LE, Great Britain} 

\author{List and order to be determined}

\begin{abstract}

We present Hubble Space Telescope Advanced Camera for Surveys (ACS) 
far ultraviolet (FUV) images of the Ly$\alpha$
and continuum emission of the luminous emission-line nebulae
in 7 galaxies from
the Rosat brightest cluster sample chosen based on their elevated H$\alpha$ flux. 
The emission in both FUV continuum and Ly$\alpha$ is resolved
over a region 5-10~kpc large.  Both continuum and line emission
contains clumps, but the Ly$\alpha$ emission also contains
a diffuse or filamentary component.
Star formation rates estimated from the FUV continuum are about 10
times lower than those estimated from the infrared, however
both the Balmer decrement in the central few arcseconds and detection
of CO in most of these galaxies imply that there are regions of
high extinction that could have absorbed much of the FUV continuum.  
Only 2 of the brightest cluster galaxies 
have resolved extended radio emission as seen with VLA archival observations.
The 4 galaxies with archival deep Chandra observations
exhibit lopsided X-ray emission.
A low feedback state for the AGN could allow 
increased condensation of the hot gas into the center
of the galaxy and feeding the star formation, however
this would not account for the lopsided X-ray morphology (if this
is significantly different than in other BCGs).
Alternately, disturbances in the intergalactic medium (IGM)
could be associated with the enhanced star formation.

\end{abstract}

\keywords{}

\section{Introduction}

Ly$\alpha$ and far-ultraviolet continuum observations provide
unique constraints on the physical properties of
the nebulae in clusters.  The far-UV continuum together with
optical and infrared observations constrain the star formation history
and the properties of young stars associated with the nebula.
The Ly$\alpha$ to H$\alpha$ or H$\beta$ flux ratio is a diagnostic
of ionization, metal and dust content \citep{ferland85,binette93}.

Cooling flow clusters exhibit extended Ly$\alpha$ emission \citep{hu92}
and far UV continuum emission \citep{odea04}.
The previous study of two brightest cluster galaxies (BCGs), 
Abell 1795 and Abell 2597 \citep{odea04},
found that the nebula exhibited both a diffuse component  Ly$\alpha$
and more compact features such as knots and filaments.
The Ly$\alpha$ emission was closely tied to the radio morphology
suggesting that star formation and associated
ionization was present at the edges of radio lobes.

In this study we enlarge the sample of objects studied
by including more distant BCGs and those with higher star formation rates.
Brightest cluster galaxies (BCGs) with high H$\alpha$ luminosities were chosen 
from the ROSAT Brightest Cluster Sample (BCS) \citep{ebeling98}.
Their H$\alpha$ luminosities are in the range $10^{42}$--$10^{43}$ erg/s.
These galaxies have been observed with the Spitzer Space Telescope 
\citep{quillen08,odea08}.

Not all cooling flow BCGs have evidence of recent or ongoing star formation 
\citep{odea08,loubser09}.  Hence BCGs exhibiting elevated rates of
star formation could be those experiencing a low level of feedback
from the AGN.   Evidence for residual cooling can be inferred from the
reservoirs of cold gas found in BCGs. Alternatively star formation
could also be attributed to stripping from a gas rich galaxy \citep{holtzman96}.
Recent estimates of condensation and star formations rates show
that in some systems are they are in near agreement 
(e.g., \citealt{odea08}).  Recently \citet{rafferty08} found that star formation
tends to occur when the central cooling time drops below
a critical value.  In this paper by resolving the region of star formation,
over a large sample of BCGs we aim to test some of these possibilities.


\section{Observations}

\begin{deluxetable*}{lcccccc}
\tabletypesize{\scriptsize}
\tablecaption{Observation Log}
  \tablewidth{0pc}
\tablehead{
    \colhead{Source} &
    \colhead{RA} &
    \colhead{Dec} &
    \colhead{z} &
    \colhead{kpc/$^{\prime\prime}$} &
   \colhead{Line/Cont}&
    \colhead{Filter}    
}
\startdata
Abell 11   & 00:12:33.87 & -16:28:07.7  & 0.151  & 2.60  & Line  & F125LP  \\
       	   &             &              &        &       & Cont. & F150LP  \\
Abell 1664 & 13:03:42.52 & -24:14:43.8  & 0.128  & 2.26  & Line  & F125LP  \\
           &             &              &        &       & Cont. & F150LP  \\        
Abell 1835 & 14:01:02.10 & +02:52:42.8  & 0.253  & 3.91  & Line  & F140LP  \\
           &             &              &        &       & Cont. & F165LP  \\
RXJ 2129+00& 21:29:39.96 & +00:05:21.2  & 0.235  & 3.70  & Line  & F140LP  \\
           &             &              &        &       & Cont. & F165LP  \\
ZWCL 348   & 01:06:49.39 & +01:03:22.7  & 0.254  & 3.92  & Line  & F140LP  \\
           &             &              &        &       & Cont. & F165LP  \\
ZWCL 3146  & 10:23:39:62 & +04:11:10.8  & 0.290  & 4.32  & Line  & F140LP  \\
           &             &              &        &       & Cont. & F165LP  \\                    
ZWCL 8193  & 17:17:19.21 & +42:26:59.9  & 0.175  & 2.94  & Line  & F140LP  \\
           &             &              &        &       & Cont. & F150LP   
\enddata
  \tablecomments{
The exposure time in each long pass filter was 1170s.
Positions are given in degrees for epoch J2000 and are measured from
radio source positions in archival VLA data at 8.5 or 5 GHz.
%Table \ref{tab:tab3} for a summary of its radio properties.
}
\label{tab:tab1}
\end{deluxetable*}


\begin{deluxetable*}{lccccc}
\tabletypesize{\scriptsize}
\tablecaption{Star Formation Rates}
 \tablewidth{0pc}
\tablehead{
    \colhead{Galaxy} &
    \colhead{M($H_2$)}  &
    \colhead{SFR$_{IR}$} &
    \colhead{SFR$_{H\alpha}$} &
    \colhead{SFR$_{FUV}$} &
    \colhead{Balmer Dec} \\
\colhead{} &
\colhead{($10^{10} M_\odot$~yr$^{-1}$)} &
\colhead{($M_\odot$~yr$^{-1}$)} &
\colhead{($M_\odot$~yr$^{-1}$)} &
\colhead{($M_\odot$~yr$^{-1}$)} &
\colhead{${H\alpha/H\beta}$} \\
}
\startdata
Abell 11      & 1.1                &  35          & 9.7         & 4.8   & ... \\
Abell 1664    & 1.9                &  15          & 5.6         &  4.6  & 5.2\\   
Abell 1835    & 7.9                &  125         & 40.5        &  11.7 & 5 \\
ZWCL 348      &                    &  52          & 15.5        &  6.1  & 4.27\\
ZWCL 3146     & 7.0                &  67          & 47.1        & 12.4  & 3.7  \\
ZWCL 8193     & 1.5                &  59          & 7.6         &  5.4  & 5.9\\
RXJ 2129+00   &                    &  13          & 2.3         &  0.9  & 2
\enddata
\tablecomments{\\
Notes on table:
Infrared estimated star formation rates are by \citet{odea08}
except for Abell 1835 and ZWCL~3146 which are by \citet{egami06}.
These star formation rates are estimated from the 
8 and 24~$\mu$m fluxes \citep{quillen08}.
Molecular gas mass estimates for Abell 11, Abell 1665, Abell 1835, and ZWCL 3146.
by \citet{edge01}, but corrected to a Hubble constant of 75~Mpc$^{-1}$~km~s$^{-1}$.
The ZWCL 8193 molecular mass is by \citet{salome03}.
Note ZWCL 3146 also contains about $10^{10}$ M$_\odot$ of warm molecular hydrogen
\citep{egami06b}.
Star formation rates are estimated from the limited-aperture observations
by \citet{crawford99} (long slit of width 1\farcs3) 
excepting for ZWCL~348 which used the H$\alpha$ flux from the 
Sloan Digital Sky Survey archive (and a 3$^{\prime\prime}$ diameter fiber).
%and A11 which is based on a Pa$\alpha$ observation by \citet{edge02}.
Neither the H$\alpha$ or UV based star formation rate estimates
have been corrected for internal extinction.
}
\label{tab:tab2}
\end{deluxetable*}



\begin{deluxetable*}{lccc}
\tabletypesize{\scriptsize}
\tablecaption{Ly$\alpha$ fluxes}
  \tablewidth{0pc}
\tablehead{
    \colhead{Source} &
    \colhead{Radius of Aperture} &
    \colhead{Flux (e$^{-1}$~s$^{-1}$)} &
    \colhead{Ly$\alpha$ Flux}  \\
    \colhead{} &
    \colhead{(\arcs)} &
    \colhead{(e$^{-1}$~s$^{-1}$)}  &
    \colhead{(10$^{-14}$ erg~cm$^{-2}$~s$^{-1}$)}  \\
}
\startdata
Abell 11       &   2   &   6.5      &  7   \\
Abell 1664     &   3   &   3.6      &  8   \\
Abell 1835     &   2   &   3.8      &  14  \\
ZWCL 348       &   2   &   2.1      &  10  \\
ZWCL 3146      &   3   &   1.7      &  15  \\
ZWCL 8193      &   2   &   15.9     &  6   \\ 
RXJ 2129+00    &   2   &   0.3      &  2   
\enddata
  \tablecomments{Fluxes were measured using aperture photometry
and an aperture that covers the bulk of the emission visible in Figures 1-7}
\label{tab:tab3}
\end{deluxetable*}


\subsection{FUV images}


Observations were obtained with the Solar Blind Chanel (SBC) MAMA 
detector of the Advanced Camera for Surveys (ACS) \citep{clampin04} 
on the Hubble Space Telescope (HST).
%
Each galaxy was observed in two long pass filters, the one containing
the Ly$\alpha$ line, the other redward of this line to measure
the continuum.
The F140LP filter containing the Ly$\alpha$ line was used for all galaxies
except the nearer BCGs, Abell 11 and Abell 1664, which were
observed using the F125LP filter.
The continuum filter chosen was 
%F140LP for objects with redshift $z<0.11$ , 
F150LP for objects with redshift
$0.11<z<0.19$ (ZWCL8193, Abell 11, and Abell 1664) and 
the F165LP filter for the remaining objects with $0.19<z < 0.31$
(Abell 1835, ZWCL348, RXJ 2129+00, ZWCL3146).
Observations were taken using a 3 point position dither.
The exposure time in each filter was 1170s 
so that the observations in the two filters was 
approximately one HST orbit per galaxy.
Observations were taken between March 2008 and February 2009.
The long pass filters,  F125LP, F140LP, F150LP, and F165LP, have 
%pivot wavelengths of 1438, 1527, 1611 and 1758$\AA$, respectively 
similar maximum wavelengths of 2000$\AA$ but
minimum or cut-off 
wavelengths of 1250, 1370, 1470 and 1650$\AA$ respectively.
The pixel scale for the SBC is approximately 0\farcs034 $\times$ 0\farcs030/pixel.
The camera field of view is 34\farcs6× 30\farcs8.
%The proposal ID is 11230. 
These  FUV observations are summarized in Table \ref{tab:tab1}.
%and it was cycle 11

The ACS/SBC images were reduced with the ACS calibration pipeline producing
calibrated drizzled images.
Continuum images were shifted to the position of the line images
and subtracted from the line images after multiplication
by an adjusted corrective factor larger than 1 to take
into account the additional continuum photons present in 
the line images.
Our procedure was to increase the correction factor until regions of
the image became negative.
FUV and continuum subtracted Ly$\alpha$ images are shown in Figures 1-7.

\subsection{Comparison images}

Observed at the same time were optical images with 
the WPFC2 camera on board HST using the broad band F606W filter
for Abell 1664, ZWCL~8193 and RXJ 2129.6+0005. 
Visible broad band images observed with WFPC2 were available from 
the Hubble Legacy Archive for the remaining galaxies 
in either the F702W filter (Abell 1835) or the F606W filter
(ZWCL 348, ZWCL 3146, and Abell 11).
The broad band optical images are shown for comparison in Figures 1-7.

We have overlayed 3$\mu$m continuum observations as contours
in Figures 1-7 on the FUV continuum images.  These images were take with the IRAC
camera on the Spitzer Space Telescope and are described
by \citet{egami06,quillen08}.
We find that the FUV and Ly$\alpha$
emission is located near the center of the 
brightest cluster galaxies as seen at 3$\mu$m.

Chandra X-ray Telescope observations with the 
(Advanced CCD Imaging Spectrometer (ACIS) were available from the
archive for four of the galaxies; 
Abell 1664, Abell 1835, ZWCL 3146, and RXJ 2129+00.
Exposure times are 11, 22, 49, and 12 ks respectively.
The event files were binned to  1\arcs pixels and the resulting
images smoothed with the {\it ciao} adaptive smoothing routine {\it csmooth} using
the algorithm by \citet{ebeling06}.
Constant surface brightness X-ray contours are shown for these
four galaxies in Figures \ref{fig:A1664},\ref{fig:A1835}, \ref{fig:Z3146}
and \ref{fig:R2129} overlayed on the continuum subtracted Ly$\alpha$ images.

Figures 1-7 have been centered at the location of the central radio
sources as measured from VLA archival data at 5 or 8.5 Ghz (with positions
listed in Table \ref{tab:tab1}).
Coordinate errors measured
from HST, Spitzer Space Telescope and ACIS Chandra 
X-ray Telescope observations are of order an arcsecond.
The FUV and Ly$\alpha$
images lack contain point sources that could be used
to register the images at sub-arcsecond scales.


\subsection{Morphology}

We find that all 7 galaxies observed display extended emission
in both FUV continuum and Ly$\alpha$ emission.
The FUV continuum is patchy, as
was true for Abell 1795 and Abell 2197 \citep{odea04}.  
As discussed by \citep{odea04} the FUV continuum
is likely associated with young stars in star clusters.
The Ly$\alpha$ morphology contains both clumps 
and a more diffuse or filamentary component.
Diffuse or filamentary Ly$\alpha$ was also seen by \citet{odea04}
in Abell 1795 and Abell 2597.
The association between the Ly$\alpha$ and FUV continuum 
implies that the FUV continuum is responsible for the ionization
of the Ly$\alpha$ emitting gas.

\subsubsection{Ly$\alpha$ and radio emission}

Only two of the radio sources, those in RXJ 2129+00 and Abell 1835, were
resolved in the VLA archival observations.   
For these two we have overlayed radio
contours on the images showing Ly$\alpha$ emission
so the orientation of the radio emission can be seen.
In neither galaxy are the radio jets clearly associated with
Ly$\alpha$ emission or lying near emitting filaments
as was true for the nearer galaxies Abell 1795 and Abell
2597 \citep{odea04}.  These two have redshifts of 0.6 and 0.8
whereas our nearest source has $z=0.15$. 
The lack of any association between Ly$\alpha$ and
radio emission in our sample may in part be due
because the sources are more distant than the nearer two galaxies
studied previously.

\subsubsection{Lopsidedness}

All our BCGs display lopsidedness.
Abell 11's bright visible nucleus coincides with the brightest region
of FUV continuum and Ly$\alpha$ emission. However this nuclear region is not
centered on the outer isophotes as seen either in visible or 3$\mu$m light 
(see Figure \ref{fig:A11}).  The FUV and Ly$\alpha$ emission both show
an additional emission region about 2\arcs west of the nucleus.
%
For Abell 1664,  3$\mu$m peak is located whether there are dust lanes
in the visible band images implying that this is the galaxy nucleus.  
The outer 3$\mu$m isophotes extend to the south-west
where there is excess X-ray emission (see Figure \ref{fig:A1664}).  
The lopsided X-ray morphology 
was also noted by \citet{kirkpatrick09}.
%
Abell 1835 also displays asymmetric X-ray contours.  Its 3$\mu$m contours
are also not centered on the brightest regions seen the FUV, Ly$\alpha$ or
visible band images (see Figure \ref{fig:A1835}).
%
For ZWCL 348 the visible and 3$\mu$m emission peaks are nearly centered
and the FUV emission peaks on the center of the galaxy.  However the visible
band image shows that the galaxy is disturbed and the outer contours
seen in at 3$\mu$m are not round (see Figure \ref{fig:Z348}).  
The Ly$\alpha$ emission extends eastwards from the nucleus much 
further than to the west. 
%
Though the FUV and L$\alpha$ emission are centered on the 3$\mu$m contours
in ZWCL 3146, again the X-ray emission is lopsided, extending south-east of
the nucleus (see Figure \ref{fig:Z3146}).
%
For ZWCL 8193 there is a nuclear bulge visible in the visible and 
3$\mu$m images. However FUV and L$\alpha$ emission is brighter
north of the nucleus, and has a spiral shape suggesting that a smaller galaxy
has been recently disrupted in the outskirts of the BCG (see Figure \ref{fig:Z8193}).
%
RXJ 2129+00 also displays lopsided X-ray emission contours extending
to the south-west.
The L$\alpha$ contours extend on only the northern-eastern side of the galaxy.
The offset between radio and Ly$\alpha$ peaks is small and so 
may be due to a registration error in the HST image (see Figure \ref{fig:R2129}).

We find that most of these BCGs display strong asymmetries or uneven distributions
in their star formation as seen from the FUV continuum images.
In additional we have 4 galaxies with 
lopsided X-ray emission with Abell 1664 previously noted by \citet{kirkpatrick09}.
The offset of the
BCG from the peak of the cluster X-ray emission is an indication
of how close the cluster is to the dynamical equilibrium state, and
decreases as the cluster evolves \citep{katayama03}.
\citet{loubser09} found that BCGs tend to lie in cooling flows
but found no correlation between the age of the BCG population
and this offset, whereas \citet{bildfell08} found that blue BCGs tend to be  
within 10~kpc of the X-ray peak.
The four galaxies we have with X-ray emission do have BCG within 10~kpc
of the X-ray emission peak, consistent with the study by \citet{bildfell08}
and are also located in cooling flows \citep{odea08}, 
consistent with the study by \citet{loubser09}.
\citet{edwards09} found that cooling flow BCGs often do not contain
young populations, whereas \citet{odea08} 
found that estimated X-ray mass deposition
rates are correlated with star formation rates.

For these galaxies, 1\arcs corresponds to 2--4~kpc (see Table \ref{tab:tab1}) thus
these asymmetries are on a scale of order 10-50 kpc.  
The high star formation rates of
the galaxies studied here compared to others in the Rosat BCG sample
may be related to the large scale X-ray structure.
We will discuss this in more detail later.
%Feedback by winds, jets or bubbles would not
%be expected to cause lopsidedness, thus the lopsidedness suggests
%large scale dynamical events such as recent perturbations or mergers
%in the cluster. 

\subsubsection{Comparison to CO and H$\alpha$ observations}

Emission from CO remained unresolved 
at a resolution 6\arcs for Abell 1835 and ZWCL 3146 \citep{edge03}. 
The nuclear 24$\mu$m emission was unresolved \citep{quillen08,egami06} for
all of the BCGs studied here, though the nuclear region was red
over a resolved region in the central few arc seconds
in the mid-IR broad band images for Abell 1664 and ZWCL 8193 \citep{quillen08}, 
For comparison the point spread function FWHM for 
IRAC camera is 1\farcs7 at 3 $\mu$m (IRAC band 1) 
and 2\farcs2 at 8 $\mu$m (IRAC band 4) and 7\arcs at 24 $\mu$m.
the two with the most extended FUV and Ly$\alpha$ emission. 
Our UV observations have higher angular resolution than
the CO or Spitzer observations but are consistent with the extent
that these previous observations were able to resolve star formation regions. 
The star formation regions in these galaxies extend a few arcseconds 
corresponding to 5-10~kpc.

Abell 1664 has been observed using integral field spectroscopy
by \citet{wilman06} in the H$\alpha$ line.  
The continuum subtracted Ly$\alpha$ emission 
images resembles the H$\alpha$ image shown as Figure 2 by \cite{wilman06}
with a bright spot about 2\arcs from the nucleus to the south west.
The bright spot we see just north of the nucleus  does
correspond to an H$\alpha$  emission feature. However
the Ly emission is brighter north west of the nucleus
rather than north east of the nucleus as is true in 
H$\alpha$.   It is likely that a more detailed comparison will
reveal a large variation in Ly$\alpha$ to H$\alpha$ ratio
suggesting either large variations in extinction or shock emission
as photoionization models to predict a narrower
range of intrinsic emission ratios \citep{ferland85,ferland86}.  

\citet{wilman06} also observed ZWCL 8193 and detected H$\alpha$ emission 
at the galaxy center and in two clumps about 3\arcs north of the galaxy 
(see their Figure 17).
Their H$\alpha$ emission more closely resembles our FUV continuum image, 
though the H$\alpha$ emission is stronger near the galaxy than north
of the galaxy and we see stronger continuum emission north of the galaxy 
than near the galaxy center.  Our Ly$\alpha$ image shows diffuse
emission over a region that is about twice the area than 
the H$\alpha$ emission.  
The Ly$\alpha$ emission exhibits a tail curving to the east from the north
and almost looks like a spiral galaxy.   The morphology suggests
a gas rich galaxy has been disrupted and its remains are forming stars in the 
vicinity of the BCG.

\subsection{Estimated Star Formation Rates}

We use the FUV continuum flux to estimate star formation rates in these galaxies.
The continuum flux was first corrected for Galactic extinction.
Extinction correction was done using Galactic extinction 
at the position of each BCG and
the extinction law by \citet{cardelli89} (as done
in Table 5 by \citealt{odea04} for Abell 1795 and Abel 2597).
We then compared the count rate predicted for the observed filter by 
{\it synphot}\footnote{http://www.stsci.edu/hst/HST\_overview/documents/synphot/hst\_synphotTOC.html}
for a spectrum produced by 
STARBURST99\footnote{http://www.stsci.edu/science/starburst99/} \citep{leitherer99,vazquez05}.
{\it synphot} is a general purpose package for synthetic photometry. 
Its utility for Hubble Space Telescope users arises from 
detailed models of HST instrument throughputs that are 
stored in the Calibration Data Base system.

The UV continuum estimated star formation rates are listed in
Table \ref{tab:tab2}.  We compare the UV continuum estimated star formation
with those based on the limited aperture H$\alpha$ fluxes by \citet{crawford99}
(using 1\farcs3 wide slit)
or spectroscopic measurements from the Sloan Digital Sky Survey archive
(using a 3\arcs diameter fiber)
and those estimated from infrared observations with the Spitzer Space
Telescope by \citet{egami06,quillen08,odea08}. 
Neither the UV continuum estimated or H$\alpha$ estimated star formation
rates have been corrected for internal extinction.
This Table also lists molecular gas masses by \citet{edge01,salome03}.

Balmer decrements are available for most of the galaxies considered
here and range from 3-5 \citep{crawford99}.   The intrinsic optical extinction
imply $E(B-V) \sim 1$ and extinctions
in the far UV of order 10.  For an extinction this high we should not
have detected any FUV continuum emission.

We note from table \ref{tab:tab2} that infrared star formation rates
exceed those estimated in H$\alpha$ and these exceed those estimated
from the FUV continuum.   This would be consistent with patchy but
significant levels of extinction.  Large levels of extinction
are also likely because of the high molecular gas content in these galaxies.

Previous comparisons between H$\alpha$ and Ly$\alpha$
flux suggested modest extinctions intrinsic to the cluster
of order E(B-V)$=$ 0.09-0.25 \citep{hu92}.  This was done assuming
an unabsorbed L$\alpha$/H$\alpha$ ratio of 13
for photoionization and collision models \citep{ferland86}.
%Shock models would cover a wider range.
However the BCGs considered by \citet{hu92} were not chosen via
their H$\alpha$ luminosity.  As H$\alpha$ luminosity is correlated
with both molecular gas mass and infrared luminosity \citep{odea08} is it perhaps not
surprising that the sample considered here would have higher estimated
internal extinctions than the same considered by \citet{hu92}.

In short, FUV estimated star formation rates are about 10 times lower
than those estimated from the Spitzer observations.
Balmer decrements and molecular gas observations suggest that internal
extinction could be extremely high in some regions.
The discrepancy between the estimated star formation rates
and the Balmer decrement suggest that internal extinction is patchy.
As the infrared estimated star formation rate is least sensitive
to extinction, it can be considered the most accurate, and
suggests that about 90\% of the FUV continuum has been absorbed.

\cite{odea08} noticed a discrepancy between the infrared estimated
star formation rates and the size of the star forming regions.
Here we have confirmed that the star forming regions are not large
and remain under 20kpc.   This puts the galaxies somewhat off
the Kennicutt relation but (as shown by \citealt{odea08} in their figure
8) but only by a modest factor of a few.  While we confirm
the discrepancy we find that it is not large enough that it could
not be explained by other systematic effects such as an overestimate
of the H$_2$ mass.  The CO to H$_2$ conversion factor is suspected 
to be lower
by a factor of a few (e.g., \citealt{israel06}) in galaxy centers
compared to disk regions.  If the same were true in these BCGs then
they would like on the Kennicutt relation.


%Blue optical colors are see
%in center of objects with short X-ray cooling timescales or
%those below$ 5 \times 10^8$ years.
%This suggests that there is a critical cooling time entropy
%threshhold for star formation \citep{rafferty08}.

%Note \citet{mcnamara06} claim this galaxy follows Kennicut Schmidt law.
%R2129 is dull at all spitzer bands.
%Z348 is unresolved at 24, maybe redish at irac bands.

\subsubsection{Ly$\alpha$ emission}
Table 3 must be discussed. xxx


\section{Discussion and Summary}

In this paper we have presented high angular resolution
images in FUV continuum and Ly$\alpha$ of 7 brightest cluster galaxies
that are actively forming stars.
The emission in both continuum and Ly$\alpha$ is resolved
over a region 5-10~kpc large.  Both continuum and line emission
contains clumps, but the Ly$\alpha$ emission also contains
a diffuse or filamentary component.

Star formation rates estimated from the FUV continuum are about 10
times lower than those estimated from the infrared, however,
both the Balmer decrement in the central arcsec and  detection
of CO in these galaxies suggest that there are regions of
high extinction.  We suspect that a substantial fraction
of the FUV emission is absorbed by internal extinction.

Comparisons between Ly$\alpha$ and existing H$\alpha$ images
suggest that there are large variations in emission line ratio.
This can be explained either by patchy extinction or
with shocks, affecting the intrinsic line ratios.

Unlike Abell 1795 and Abell 2597 \citep{odea04}, we find no
relation between the Ly$\alpha$ morphology and the 
radio morphology in our galaxies.  While both of these galaxies 
host star formation, it is at a lower level than
estimated for the 7 of our sample.
With the exception of Abell 1835 and RXJ 2129+00, the radio emission
at 5 or 8 GHz GHz (from archival VLA observations)
is not resolved suggesting that these sources
have fairly compact radio structures.
This could be because nuclear fueling has been reduced by a previous
AGN activity cycle and we are now seeing the galaxies following 
a period of relative quiescence.  It is tempting to also account for
the high star formation rate with a period of low feedback.  
Rapid cooling in the IGM fueling
the current high star formation may be due to a previous reduction 
in energy deposited into the IGM.

We have also noted that most of our galaxies exhibit asymmetries in
their distribution of star formation and 4 of them show lopsided
X-ray contours.  Feedback from an AGN (jets and bubbles) would not
be expected to push the X-ray emitting gas off-center.
However disturbances in the IGM could lead to higher cooling rates
in the gas as the cluster relaxes and slowly evolves
to equilibrium.   \citet{kirkpatrick09} find that cooling rates
could be high enough to fuel the star formation in Abell 1664.
Similar cooling rates have been estimated for most of the other 
galaxies in our sample \citep{odea08}.
If the high star formation rates are related to large disturbances
in the IGM the radio quiescence of these sources requires 
another explanation.   The large estimated molecular gas mass,
Balmer decrements, discrepancies between star formation rates
estimated in FUV continuum, H$\alpha$,  and infrared imply
that there is dense gas in these galaxies.   We have resolved
the regions of star formation and find that this dense gas
is likely to be within the central 10-20 kpc.   In this case
radio jets could be frustrated as is thought to happen in CSS sources.


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\clearpage



\begin{figure*}
\begin{center}$
\begin{array}{cc}
\includegraphics[angle=0,width=3.0in]{A0011_f606w.eps}  &
\includegraphics[angle=0,width=3.0in]{A0011fuv.eps} \\
\includegraphics[angle=0,width=3.0in]{A0011ly.eps} & \\
\end{array}$
\end{center}
%\plottwo{A0011_f606w.eps}{A0011fuv.eps}
\caption{
a) (upper left) Visible band HST image of Abell 11 in the F606W filter.
b) (upper right) FUV continuum image.
The FUV continuum image has 3$\micron$ contours overlayed.
Contour separation is a factor of two in surface brightness.
The 3 $\micron$ image is a Spitzer IRAC band 1 image.
c) (lower left) Continuum subtracted Ly$\alpha$ image.
\label{fig:A11}
}
\end{figure*}

\begin{figure*}
%\plottwo{A1664_f606w.eps}{A1664fuv.eps}
%\plottwo{A1664ly.eps}{A1664ly_xray.eps}
\begin{center}$
\begin{array}{cc}
\includegraphics[angle=0,width=3.0in]{A1664_f606w.eps}  &
\includegraphics[angle=0,width=3.0in]{A1664fuv.eps} \\
\includegraphics[angle=0,width=3.0in]{A1664ly.eps} & 
\includegraphics[angle=0,width=3.0in]{A1664ly_xray.eps} \\
\end{array}$
\end{center}
\caption{
a) (upper left) Visible band HST image of Abell 1664 in the F606W filter. 
b) (upper right) FUV continuum image overlayed with 3$\micron$ contours.
c) (lower left) Continuum subtracted Lyman $\alpha$ image of Abell 1664.
d) (lower right) Continuum subtracted Ly$\alpha$ image with X-ray contours.
%The X-ray image is a smoothed 0.3-5keV ACIS Chandra 11.4~ks image. 
\label{fig:A1664}
}
\end{figure*}

\vfill\eject
\clearpage

\begin{figure*}
\begin{center}$
\begin{array}{cc}
\includegraphics[angle=0,width=3.0in]{A1835_f702w.eps}  &
\includegraphics[angle=0,width=3.0in]{A1835fuv.eps} \\
\includegraphics[angle=0,width=3.0in]{A1835ly_radio.eps} & 
\includegraphics[angle=0,width=3.0in]{A1835ly_xray.eps} \\
\end{array}$
\end{center}
\caption{
a) (upper left) Visible band HST image of Abell 1835 in the F702W filter. 
b) (upper right) FUV continuum image overlayed with 3$\micron$ contours.
c) (lower left) Continuum subtracted Ly$\alpha$ image of Abell 1835 (grayscale) with
5GHz radio contours.
d) (lower right) Continuum subtracted Ly$\alpha$ image with X-ray contours.
%The X-ray image is a smoothed 0.3-5keV ACIS Chandra 22~ks image. 
\label{fig:A1835}
}
\end{figure*}

\vfill\eject
\clearpage

\begin{figure*}
%\plottwo{ZWCL0348_f606w.eps}{ZWCL0348fuv.eps}
%\plottwo{ZWCL0348ly.eps}{blank.eps}
\begin{center}$
\begin{array}{cc}
\includegraphics[angle=0,width=3.0in]{ZWCL0348_f606w.eps}  &
\includegraphics[angle=0,width=3.0in]{ZWCL0348fuv.eps} \\
\includegraphics[angle=0,width=3.0in]{ZWCL0348ly.eps} & \\
%\includegraphics[angle=0,width=3.0in]{A1835ly_xray.eps} \\
\end{array}$
\end{center}
\caption{
a) (upper left) Visible band HST image of ZWCL 348 in the F606W filter. 
b) (upper right) FUV continuum image overlayed with 3$\micron$ contours.
c) (lower left) Continuum subtracted Lyman $\alpha$ image of ZWCL 348.
\label{fig:Z348}
}
\end{figure*}

\vfill\eject
\clearpage

\begin{figure*}
%\plottwo{ZWCL3146_f606w.eps}{ZWCL3146fuv.eps}
%\plottwo{ZWCL3146ly.eps}{ZWCL3146ly_xray.eps}
\begin{center}$
\begin{array}{cc}
\includegraphics[angle=0,width=3.0in]{ZWCL3146_f606w.eps}  &
\includegraphics[angle=0,width=3.0in]{ZWCL3146fuv.eps} \\
\includegraphics[angle=0,width=3.0in]{ZWCL3146ly.eps} & 
\includegraphics[angle=0,width=3.0in]{ZWCL3146ly_xray.eps} \\
\end{array}$
\end{center}
\caption{
a) (upper left) Visible band HST image of ZWCL 3146 in the F606W filter. 
b) (upper right) FUV continuum image overlayed with 3$\micron$ contours.
c) (lower left) Continuum subtracted Lyman $\alpha$ image of ZWCL 3146.
d) (lower right) Continuum subtracted Ly$\alpha$ image with X-ray contours.
%The X-ray image is a smoothed 0.3-5keV ACIS Chandra 49ks image. 
\label{fig:Z3146}
}
\end{figure*}

\begin{figure*}
%\plottwo{ZWCL8193_f606w.eps}{ZWCL8193fuv.eps}
%\plottwo{ZWCL8193ly.eps}{blank.eps}
\begin{center}$
\begin{array}{cc}
\includegraphics[angle=0,width=3.0in]{ZWCL8193_f606w.eps}  &
\includegraphics[angle=0,width=3.0in]{ZWCL8193fuv.eps} \\
\includegraphics[angle=0,width=3.0in]{ZWCL8193ly.eps} & \\
%\includegraphics[angle=0,width=3.0in]{A1835ly_xray.eps} \\
\end{array}$
\end{center}
\caption{
a) (upper left) Visible band HST image of ZWCL 8193 in the F606W filter. 
b) (upper right) FUV continuum image overlayed with 3$\micron$ contours.
c) (lower left) Continuum subtracted Lyman $\alpha$ image of ZWCL 8193.
\label{fig:Z8193}
}
\end{figure*}

\vfill\eject
\clearpage




\vfill\eject

\begin{figure*}
%\plottwo{R2129_f606w.eps}{R2129fuv.eps}
%\plottwo{R2129ly.eps}{R2129ly_xray.eps}
\begin{center}$
\begin{array}{cc}
\includegraphics[angle=0,width=3.0in]{R2129_f606w.eps}  &
\includegraphics[angle=0,width=3.0in]{R2129fuv.eps} \\
\includegraphics[angle=0,width=3.0in]{R2129ly.eps} & 
\includegraphics[angle=0,width=3.0in]{R2129ly_xray.eps} \\
\end{array}$
\end{center}
\caption{
a) (upper left) Visible band HST image of RXJ 2129+00 in the F606W filter. 
b) (upper right) FUV continuum image overlayed with 3$\micron$ contours.
c) (lower left) Continuum subtracted Lyman $\alpha$ image of RXJ 2129+00 overlayed
with 8 GHz radio contours.
d) (lower right) Continuum subtracted Ly$\alpha$ image with X-ray contours.
%The X-ray image is a smoothed 0.3-5keV ACIS Chandra 12ks image. 
\label{fig:R2129}
}
\end{figure*}


\end{document}
