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\begin{document}

%%% The proposal consists of these sections:
%
%   Scientific justification & Experimental design: up to 2 pages of text
%   References, Figures, target list, and publications: up to 2 pages
%	

\section{Scientific Justification}

Ultra-diffuse galaxies (UDG; van Dokkum et al.  2015a) were identified from
deep ground-based observations performed with the Dragonfly telescope array
(Abraham \& van Dokkum 2014) as extended ($r_e>1.5$~kpc) low surface
brightness ($\mu_{0,g}>24$~mag~arcsec$^{-2}$) galaxies populating the Coma
cluster.  With the sizes comparable or sometimes exceeding the Milky Way
size, these galaxies have stellar masses of 0.1\%$-$1\%\ that of the Galaxy. 
The initial sample of 47 Coma UDGs grew to 854 (Koda et al.  2015) found in
deep Subaru Suprime-Cam images, 271 of which turned to be larger than the
Milky Way.  Later, UDGs were detected in other galaxy clusters and groups
(see Appendix A in Yagi et al.  2016).  All Coma cluster UDGs have
integrated colors compatible with old passively evolving stellar populations
(Koda et al.  2015).

Extremely low surface brightness levels in UDGs prevent their efficient
studies using ground based spectroscopy.  Only a few UDGs have spectroscopic
measurements of their radial velocities confirming their Coma cluster
membership (van Dokkum et al.  2015b; Kadowaki et al.  2017), but no stellar
velocity dispersion measurements have been carried out so far.  UDGs are
hypothesized to be heavily (98\%-99\%; van Dokkum et al.  2015a, Koda et al. 
2015) dark matter dominated and sometimes even called ``dark galaxies'' even
though no internal dynamics measurements can confirm this claim.  The
formation mechanisms for UDGs remain purely speculative because no
observational data can confirm/refute any scenario (slow star formation in a
shallow primordial dark matter potential well, interstellar medium (ISM)
stripping from disky progenitors by SN feedback and/or ram pressure, star
formation quenching by tidal stirring in a cluster, etc.)

The only ``easy'' option on the table is to find UDGs in the early stage
of evolution when their stars are still young and, therefore, the surface
brightness is comparable to that in normal disk galaxies.  Recently, we have
identified a sample of 13 very unusual blue extended diffuse post-starburst
(PSG) galaxies in the Sloan Digital Sky Survey DR7 (Abazajian et al.  2009)
using our stellar population analysis presented in the Reference Catalog of
Spectral Energy Distributions (RCSED, Chilingarian et al.  2017).  This
sample includes all galaxies in the SDSS primary sample with H$\alpha$
emission not exceeding the 10$\sigma$ detection in order to exclude star
forming objects, simple stellar population ages younger than 2~Gyr and the
k-corrected color $g-r<0.55$~mag.  10 of 13 galaxies turned to be Coma
cluster members, 2 others are hosted by the double galaxy cluster
Abell~2147/2197, and 1 is in the compact galaxy group SDSSCGA~01018.

We retrieved archival optical images from the Canada-France-Hawaiian
Telescope and Subaru for 12 cluster galaxies and near-infrared Spitzer Space
Telescope images at 3.6, 4.5, 5.8, and 8$\mu$m for 10 Coma galaxies.  All of
them have effective radii between 1.8 and 4.0~kpc, quite regular morphologies,
mean stellar ages between 300 and 750~Myr and central surface brightness
levels about $\mu_0,g$=20.5--22.0~mag~arcsec$^-2$.  Most of them are
strongly flattened suggesting their disky morphology.  If those objects
continue to evolve passively in 5--7~Gyr they will all end up as UDGs
because their surface brightness will decrease by 2--4~mag/arcsec$^-2$. Two
galaxies have archival HST images where complex shell structures are seen
suggesting that the galaxies experienced strong star burst episodes before
they have been stripped.

Three galaxies in Coma exhibit prominent straight tails up-to 250~kpc long
supposedly formed by the material stripped by the ram pressure (Gunn \& Gott
1972). Only the brightest and largest galaxy is detected at 5.8$\mu$m, none
is detected at 8$\mu$m and two longer WISE bands (12 and 22$\mu$m) which
supports our claim of the lack of star formation based on optical spectra.
Our novel spectrophotometric fitting technique NBursts+phot (Chilingarian \&
Katkov 2012) uses SDSS spectra simultaneously with the FUV-to-NIR broadband
photometry and allows us to robustly disentangle young recently formed stars
and old underlying stellar population. None of our galaxies is dominated by
old stars by mass, therefore our estimates of the surface brightness dimming
as a result of passive evolution must be valid.

The 13 blue diffuse PSGs suggest that the UDGs are normal low surface
brightness disk galaxies which had been slowly forming stars until they
entered the central region of a galaxy cluster, where the ram pressure
compressed the ISM and induced a short but intense burst of star formation
until it was quenched by the increasing ram pressure that swept away the
remaining ISM to the intracluster space.

The SDSS spectra have insufficient spectral resolution to confidently
measure internal velocity dispersion and estimate dynamical masses and also
lack spatial information.  Obtaining spatially resolved major axis
kinematics ($v, \sigma$) and stellar populations (age, [Fe/H]) will allow us
to answer the following questions: (a) are they dark matter dominated?  (b)
are they rotationally supported?  (c) do they have positive stellar age and
negative metallicity gradients consistent with outside-in ram pressure
stripping scenario?  If the answers are ``no'' to the first and
``yes'' to the second and third question, we will solve the UDG formation
puzzle.

\section{Experimental Design} 

Our goal is to observe the complete sample of 13 SDSS selected diffuse PSGs. 
Because 12 of 13 galaxies are hosted in rich cluster, we can use the MOS
capability of Binospec in order to observe more than 1 object at a time
using tilted slits.  In June/2017 we had a Fast Turnaround program approved
at Gemini-North and obtained data for one galaxy (3.2h integration time;
1200gpm grating, R=2700).  We successfully reconstructed major axis
kinematics and stellar populations and proved the feasibility of our
project.  Binospec has better throughput in the blue and also slightly
higher spectral resolution with the 1000gpm grating.  In fact, we observed 2
targets in Dec/2017 with Binospec in one mask with tilted slits and proved
that in 1h20min we have comparable integration to 2.5h with GMOS.

In 2018A we propose to obtain deep long-slit spectra of 8 blue diffuse PSGs:
6 in the Coma cluster (3 masks) and 2 in Abell 2147/2197 (1 mask) using the MMT Binospec
spectrograph with the 1000gpm grating centered at 4600~\AA\ and a
1-arcsec-wide slit.  The requested setup will provide us the R=4500
resolving power which will allow us (for a signal-to-noise ratio of 12-15
per pixel) to reliably measure velocity dispersions down to $\sigma=15$~km/s
and radial velocities as accurate as 2~km/s and, therefore, perform the
dynamical modeling of our galaxies even in the dark matter free case, where
we expect $\sigma \sim$~30~km/s.  We expect that we will reach S/N=15 in 2.5
hours of integration on dark sky. The requested setup will cover the
wavelength range containing a lot of weak metal lines which will provide a
handle on the stellar age/metallicity and will allow us to detect and
measure stellar population gradients.

We request an eqiuvalent of 1.3 nights (10h + overhead) in the queue mode.
As a special calibration we will need high signal-to-noise spectral
twilight flats to be taken in the requested Binospec setup. The
availability of flux calibrated SDSS spectra will allow us to easily
calibrate our data without observing spectrophotometric standards for every
object.

%Fig.~1 is a fairly direct demonstration of project
%feasibility. A 20h exposure with MMIRS at Magellan (Oct/2014) of a
%relatively bright (J(AB)=24.3~mag) high-redshift candidate ($z_{phot}=6.94$)
%clearly reveals a continuum securely identifying an object as a cool brown dwarf 
%(T7--T8 spectral type) located some 1~kpc from the Sun likely in the thick
%disk of the Milky Way.

\section{Figures} 

\vskip -20pt
\noindent
\begin{figure}[H]
\centering
\includegraphics[width=\hsize]{587741602572730542_specphot_fit.pdf}
\caption{An example of a full spectrophotometric
fitting of a Coma diffuse blue PSG (objid=587741602572730542) using the NBursts+phot 
technique. The spectrum is represented by 2 simple stellar populations: t=1~Gyr,
[Fe/H]=-0.51~dex (red) and t=120~Myr, [Fe/H]=-0.3~dex (green). The left
panel shows the SDSS spectrum, the right panel presents the broadband SED
which includes GALEX FUV/NUV, SDSS $ugriz$, UKIDSS $YJHK$, and Spitzer
IRAC1/2 measurements in a 3~arcsec aperture centered on the galaxy, which
corresponds to the SDSS fiber.}
\end{figure}

%\vskip -20pt
\begin{figure}[H]
\centering
\includegraphics[width=0.48\hsize]{587741723360559252_CFHT_g_HST.png} 
\includegraphics[width=0.51\hsize]{j1259p2815_prof_kin.png}
\caption{
A blue post-starburst galaxy J1259+2815 observed with GMOS (left) and its
recovered internal kinematics (right): radial velocity profile and velocity
dispersion. According to the preliminary results of dynamical modelling done
by a student (A.Afanasiev), the kinematics is consistent with the dynamical
M/L ratio of 1.1 in the V bands in Solar units, which suggests very little
dark matter at best.}
\end{figure}


\newpage
\section{Progress of the continuing project}

4 nights allocated in Jul/2017 on BlueChannel, 100\% lost to weather. 4h
allocated at GMOS@Gemini-North as a fast turnaround program (N2017A-FT-22),
data reduced and analysed; 1.3h of Binospec (2017C) -- reduced.

\section{Previous OIR time awards and relevant publications}
\begin{itemize}
\itemsep 0pt
\item Distant galaxies: 6 nights with MMIRS@Magellan in 2014B/2015A (3
nights lost to instrument) -- data reduced and analysed,
{\bf 1 paper published + 2 in prep}; 20 nights with MMIRS@MMT in 
2015C-2017C (9 lost) -- data reduced; analysis in progress;
\item LCO Stellar Library: 26 nights allocated in 2013A-2017A at Magellan;
observatons finished; {\bf 2 papers in prep}; 4 conference presentations; 
FIRE data reduction pipeline developed; data reduction in progress
\item LMC Star Clusters: 2 nights with MagE@Magellan in 2016B {\bf 1 paper
submitted}
\item Intermediate mass black hole confirmation: 3 half-nights of DDT using
MagE@Magellan in Jul-Aug/2017; {\bf 1 paper submitted + 1 in prep}
\end{itemize}

\noindent \textbf{Relevant Publications: Data Analysis, Big Data Approach}\\
\vskip -2mm

\begin{small}
\noindent \textbf{1.} \textbf{Chilingarian I., Zolotukhin I., Katkov I.},
Melchior A.-L., Rubtsov E., \textbf{Grishin K.}, 2017, ApJS, 228 14: \textit{RCSED -- A Value-added Reference Catalog of Spectral Energy Distributions of 800,299 Galaxies in 11 Ultraviolet, Optical, and Near-infrared Bands: Morphologies, Colors, Ionized Gas, and Stellar Population Properties}\\
\noindent \textbf{2.} \textbf{Chilingarian I.} et al. 2007, proc. of IAUS 241, 175:
\textit{NBursts: Simultaneous Extraction of Internal Kinematics and
Parametrized SFH from Integrated Light Spectra}\\
\noindent \textbf{3.} \textbf{Chilingarian I., Katkov I.} 2012, proc. of IAUS 284,
26: \textit{NBursts+phot: parametric recovery of
galaxy SFHs from the simultaneous fitting of spectra and
broad-band spectral energy distributions}\\
\noindent \textbf{4.} \textbf{Chilingarian I.} 2009, MNRAS, 394 1229:
\textit{Evolution of dwarf early-type galaxies - I. Spatially resolved
stellar populations and internal kinematics of Virgo cluster dE/dS0
galaxies}\\
\noindent \textbf{5.} \textbf{Chilingarian I.} \& \textbf{Zolotukhin I}, 2015 Science 348 418:
\textit{Isolated compact elliptical galaxies: Stellar systems that ran
away}
\end{small}

\section{Description of Collaboration} 

\textbf{IC} serves as a PI.  He discovered diffuse blue PSGs and developed
the major part of the NBursts+phot spectrophotometric fitting technique.  IC
plans observations and leads the data reduction.  He also coordinates the
collaboration between CfA and Moscow State University (Russia).  \textbf{KG}
is an undergraduate student in Moscow, a co-author of the RCSED catalog
paper; he is currently responsible for collecting and processing archival
photometric data from CFHT, Subaru, Spitzer, and HST.  He performs 1D and 2D
light profile decomposition of galaxy images.  \textbf{AA} is a MSc student
in Moscow, he is responsible for dynamical modelling.  \textbf{IK}
contributed to the NBursts+phot development and will analyze the data. 
\textbf{IZ} connects the ram pressure stripping efficiency to X-ray
properties of the clusters (e.g.  positions of shock fronts)

\section{Target List}

\begin{tabular}{|l|c|c|c|c|}
\hline
Target & R.A.(J2000) n& Dec (J2000) & Mag ($r$) & Host Cluster \\
\hline
% SDSS J024912.86-081525.7 & 02:49:12.86 & -08:15:25.7 & 18.0 & $(1.5 \pm 0.2)\cdot10^5$\\
SDSS J160154.20+160016.7 & 16:01:54.20 & +16:00:16.7 & 17.3 & Abell 2147/97\\
SDSS J125842.58+274537.7 & 12:58:42.58 & +27:45:37.7 & 16.7 & Coma\\
SDSS J125832.28+282240.7 & 12:58:32.28 & +28:22:40.7 & 17.1 & Coma\\
SDSS J125624.46+294817.7 & 12:56:24.46 & +29:48:17.7 & 17.5 & Coma\\
\hline
\end{tabular}

\section{References}
\vskip -10pt
{\scriptsize

Abazajian et al.  2009, ApJS 182 543: \textit{The Seventh Data Release of the Sloan Digital Sky Survey} \\
Abraham \& van Dokkum 2014, PASP 126 55: \textit{Ultra-Low Surface Brightness Imaging with the Dragonfly Telephoto Array}\\
Chilingarian \& Katkov 2012 IAUS 284 26: \textit{NBursts+phot: parametric recovery of galaxy star formation histories from the simultaneous fitting of spectra and broad-band spectral energy distributions}\\
Chilingarian et al.  2017, ApJS 228 14: \textit{RCSED: A Value-added Reference Catalog of Spectral Energy Distributions of 800,299 Galaxies in 11 Ultraviolet, Optical, and Near-infrared Bands: Morphologies, Colors, Ionized Gas, and Stellar Population Properties} \\
Gunn \& Gott 1972, ApJ 176 1: \textit{On the Infall of Matter Into Clusters of Galaxies and Some Effects on Their Evolution} \\
Kadowaki et al.  2017, ApJ 838 21: \textit{Spectroscopy of Ultra-diffuse Galaxies in the Coma Cluster} \\
Koda et al.  2015, ApJ 807L 2: \textit{Approximately a Thousand Ultra-diffuse Galaxies in the Coma Cluster}  \\
van Dokkum et al.  2015a, ApJ 798L 45: \textit{Forty-seven Milky Way-sized, Extremely Diffuse Galaxies in the Coma Cluster} \\
van Dokkum et al. 2015b, ApJ 804 30: \textit{Spectroscopic Confirmation of the Existence of Large, Diffuse Galaxies in the Coma Cluster} \\
Yagi et al.  2016, ApJS 225 11: \textit{Catalog of Ultra-diffuse Galaxies in the Coma Clusters from Subaru Imaging Data}
}



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