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\documentclass[10pt]{saltproposal}



\usepackage{lmodern}

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\usepackage{graphicx}

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\begin{document}

	

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	% Scientific rationale.

	\ScientificRationale{

		% Insert your scientific rationale here.

According to the present paradigm acting within the LCDM cosmological model,

galaxies form hierarchically, from dwarfs to giants, by consequent mergers.

Morphological differences between spheroidal (elliptical, following Hubble's

classification scheme) and disk (spiral and lenticular) galaxies are explained

in the frame of this paradigm by episodes of smooth pristine gas accretion from 

their own galactic halos, occuring between the merging events; disk galaxies are

those which are caught during these quiescent periods of their lifes. However,

in the frame of this classical scenario the giant elliptical galaxies must

be the youngest, and dwarf galaxies must be the oldest. In reality, observations

demonstrate the opposite trend: the giant early-type galaxies have the oldest

stellar populations and have been completely shaped at the epoch before $z=1$, 

while the low-luminosity galaxies continues their star formation to the present

epoch.



There is common opinion that lenticular galaxies have formed from spirals

by quenching star formation in their disks under the environmental influence.

The so called Butcher-Oemler (1978) effect -- an appearance of blue disk galaxies

at the redshift of 0.4 in rich clusters which lack such blue galaxies at $z=0$ --

is treated now as an observational evidence of a rather recent epoch of

S0 formation. Since blue (spiral?) disk galaxies are replaced in clusters 

by red (S0) disk galaxies at $z=0.4$ (Fasano et al. 2000), or only 4 Gyr ago 

according to the cosmological timescale in the frame of the LCDM model, then the stellar 

population of large-scale disks of S0s in present-day clusters must be of intermediate

age. Also in the frame of this paradigm we would expect solar magnesium-to-iron

ratio in stars of the disks because during 10 Gyr before the transformation

continuous star formation in the disks would produce just the solar chemical

composition, if we refer to the disks of nearby spiral galaxies.



{\bf Dating of morphological transformations of S0s.} One possible way to

trace the evolution of galaxies is to study in detail the properties of

stellar populations in nearby galaxies which can be observed with a very high

accuracy. Concerning the problem under consideration, we can determine the

present ages of the large-scale stellar disks in nearby S0s and so to date

the epoch of star formation quenching, if any took place. We have undertaken deep long-slit

spectroscopy of a small sample of nearby S0s over diverse types of environments

at the Russian 6m telescope. We have found that 60\%$\pm$13\%\ of the sample

S0s have very old outer disks (see left panel of Fig.1), with the quenching epoch of at least 10 Gyr 

ago and in addition to that are magnesium-overabundant and were therefore formed 

over a short period of time (Sil'chenko et al. 2012).

Though the sample was very small, only 20 galaxies, we have had a hint on an

environmental tendecy in our results: field S0s may have rather young stellar

disks, $T_{SSP}\approx 8$~Gyr, while all the galaxies in dense environments, in Virgo

cluster and in rich groups, have very old large-scale stellar disks.

Similar results were obtained in the frame of multi-band photometry approach 

by Prochaska Chamberlain et al. (2011) and Roediger et al. (2011). The recent study

of the Virgo-cluster S0s by Johnston et al. (2014) has shown that all the S0 galaxies

for which they have found the parameters of the disk stellar populations, have old

(older than 10 Gyr) and magnesium-overabundant large-scale stellar disks. This fact

is in contradiction with the scenario according to which S0s were born in clusters

at $z=0.4$. Following these results, the epoch of S0 formation must be put at

$z>2$, and had therefore to be very short. Keeping it in mind, we would rather prefer

to accept the following sequence of evolutionary stages for massive disk galaxies 

which is indeed observed at high redshifts:

brief effective star formation in gas-rich clumpy disks at $z\approx 2$ (Bournaud et al. 

2007) and more quiescent secular evolution including bar effects and gas redistribution

between the disk and the bulge area at $z<1$ (Kraljic et al. 2012). 

By accepting the described evolutionary scenario for disk galaxies, we would expect a dominance 

of S0-galaxies among disk galaxies between $z=2$ and $z=1$, after finishing the epoch of star-forming

clumpy disks, and their subsequent morphological evolution completely depending 

on the external gas accretion regime. If this accretion is smooth and persistent,

we would obtain a spiral galaxy with the cold, thin stellar disk and a continuous

star formation. If, due to some obstacles, the accretion is absent or sporadic,

we would obtain a lenticular galaxy with a smooth, old stellar disk and without regular 

star formation. Obviously, clusters of galaxies, with their tidal perturbances and hot intracluster

medium, are the worst place to sustain smooth accretion of the outer

cold gas, which would cause the S0 galaxies, with old stellar disks, to dominate in the clusters at the

present epoch.

 

{\bf Environmental effect.} It is very important to verify whether the age of S0 disks

correlates with the environmental density. The present-day paradigm relates S0

formation by SF quenching in spiral disks to environment effects which are

effective only in clusters and rich groups: ram pressure by X-ray gas, gravitational

tides from neighbouring galaxies and from the cluster/group potential which are

thought to be main agents of gas removal and SF quenching, all act only

in dense environments. According to the hierarchical paradigm of the modern

cosmology, the clusters and massive groups are the last to assemble their content,

so the disks of S0s in clusters must be {\bf the youngest}. If the relation is opposite,

as our and other recent results imply, the scenario must be revisited. Presently, we

have two S0 samples studied: (1) a sample of $\sim$20 nearby S0s mostly in loose groups, where

two thirds of the disks are older than 10~Gyr, and (2) a sample of 18 completely

isolated S0s partly observed with the SALT during three semesters (Katkov, Kniazev, Silchenko 2014),

where the ages of the disks cover homogeneously the range of 1--15~Gyr (see right panel of Fig.1).

Now is \underline{\bf the time} to probe another extremity

of the environment -- southern S0s in clusters.

	}

	

	% Immediate objectives.

	\ImmediateObjectives{

		% Insert your immediate objectives here.

By using {\bf the same method as for the sample of completely isolated SOs}, we plan to obtain

long-slit spectra for a sample of nearby S0 galaxies in clusters:

in the full spectral range (3700--6900~\AA) with medium spectral resolution ($R\sim 1000$).

The spectra will be used to derive stellar population ages, metallicities,

and magnesium-to-iron ratios by (1) calculating Lick indices along the slit --

the method for the RSS with this grating and slit was calibrated by Kniazev \& Silchenko (2012)

and

(2) to perform full spectral fitting of the observed spectra,

using {IDL}-based package \textsc{NBursts} from Chilingarian et al. (2007); this method

is accurate, it is the only posiible one when strong emission lines contaminate the Balmer

absorption lines, but it is inapplicable to the magnesium-overabundant stellar populations.

The exposures must be deep enough to reach the outermost disk

regions. The proposed sample of the galaxies includes members of 8 southern

rich clusters. We have selected 4--7 S0 (according to NED and HyperLEDA)

galaxies in every cluster, taking them from the range of absolute magnitudes of $M_B=-18 - -20.5$,

therewith making sure that they

are not dwarfs, while at the same time not relating to very luminous S0s which may have

quite particular origin beyond the common evolutionary paths of disk galaxies

(Van den Bergh 1990, Barway et al. 2009).

	}

	

    % Completion requirements.

    \CompletionRequirements {

        % Insert your data requirements for completing the proposal here.

As it was written above, (1) a sample of nearby S0s mostly in loose groups

consists of 20 galaxies (Sil'chenko et al. 2012, Sil'chenko 2013);

(2) a sample of completely isolated S0s consists of 18 galaxies

(Katkov, Kniazev, Silchenko 2014).

For that reason, we would finally like to have the same level of statistic and

plan to have deep long-slit data for $\sim$20 S0s in clusters from our total sample

of 48 galaxies in the submitted list.

    } 

	

	% Technical justification.

	\TechnicalJustification{

		% Insert your technical justification here.

For the accurate derivation of stellar population ages and metallicities

we need {\bf (1)} to cover a spectral range 4700--5600~\AA\ with a high

signal-to-noise (S/N) ratio;

{\bf (2)} to have the highest medium spectral resolution ($R > 1000$)

to estimate velocity dispersion;

and {\bf (3)} to reach a reasonable S/N ratio during a reasonable amount of

integration time. All these requirements can be met with the RSS spectrograph

at the SALT, using grating GR900 and slit 1.25 arcsec width.



For the accurate derivation of gas kinematics, metallicities, and densities,

and also to derive the corrections for the emission-line contamination of

the Lick index H-beta by using the H-alpha emission-line equivalent width,

we need to cover a spectral range 4300--6750~\AA\ with a moderate signal-to-noise ratio.



The RSS simulator allows us to estimate the final S/N$\sim$15 at $\lambda$5500 \AA\

for the level $\mu(V) \sim 22.0$~mag/sq.arcsec (some outer part of the disk)

with dark moon conditions, seeing about 2.0--3.0 arcsec, slit width of 1.25 arcsec

and exposure times $6\times 1400$sec.

We also require observations of spectrophotometric standards, 

as minimum once per observational set, and a reference spectrum together with

flat-fields once per track.



All our previously taken SALT data proves that our selected spectral region

and spectral resolution are enough to study the kinematics of stars and gas separately.

To derive a statistically significant result we plan to collect data for the sample

consisting of 20 galaxies from the nearest clusters.

All our clusters with the exception of Abell S0805 have coordinates where

the REAL track length is ABOUT 3600s.

With one hour track ($\sim$3600s) we can observe each galaxy for about $2\times 1400$sec

and therefore we need 3 tracks to reach the requested S/N.

For that reason we apply for a total of 216000sec of dark time for this project.



All clusters are located in the range of RA = 01h--19h leading to our application

for this program as {\bf a long-term program}, where we plan to split the total

requested time into two semesters with 108000sec each.\\



{\bf Notes to TAC remarks:}\\

1. Our requested study is proposed to use {\bf BOTH} methods for the analysis of the obtained

data:

Lick indices and \textsc{NBursts} analysis in the same style as it {\bf HAS BEEN DONE}

before with our previous samples of S0 in other environments. We explain it everywhere

in our proposal, and for that reason we do not see ANY room for ANY

systematic differences to compare the results for our different samples.\\

2. Our work with Lick indices does not request any additional long-time calibrations,

since this method was CALIBRATED for SALT during RSS comissionnig time.\\

3. Our comparison of the results obtained earlier by both methods (Lick indices and \textsc{NBursts}) shows that

they produce totally COMPARABLE results for S0 galaxies (for example, right panel of Fig.2),

and we check it every time for each studied galaxy.\\

4. Even taking into account the advent of modern methods like \textsc{NBursts}, which

used ``high-resolution, well calibrated stellar libraries'',

we need to note here that the {\bf ONLY} Lick indices method gives a possibility

to define Mg/Fe ratio.\\

5. We do not accept the disbelief of the referees expressed concerning the morphological classification

of galaxies in NED and HyperLEDA. In any case, every target image is inspected BY EYE to assure ourselves

that it is a regular disk galaxy lacking spiral arms, in other words, S0. As for the galaxy mass as a discriminator

of its evolution path, we have selected our sample in the absolute-magnitude range of --18 to --20.5 (in B) 

TO MATCH THE CORRESPONDING ABSOLUTE-MAGNITUDE RANGES taken for the samples studied before, namely, for the

sample of group S0s and for the sample of isolated S0s, to make the comparison physically motivated.

This point has been already noted in our previous Proposal.  

}

	

	% Role of the PI.

	\RoleOfPI{

		% Insert the role of the PI here.

This project is a result of long-term collaboration between PI and Prof. Olga Sil'chenko.

All spectral data reduction will be done by PI.

Lick index measurements and analysis will be done by Prof. Sil'chenko

and \textsc{NBursts} analysis will be done with help of her team.

The PI is involved in the subsequent data analysis and discussions.

	}



	% References.

	\References{

		% Insert your references here.

		% References are added in pairs:

		%

		% \ReferencePair{A}{B}

		%

		% A appears in the left column, B in the right column.

		%

		% Examples:

		% \ReferencePair

		%    {Binette et al. 1994, A\&A, 292, 13}

		%    {Finkelman et al. 209, MNRAS, 390,  969}

		% \ReferencePair

		%    {de Zeeuw \& Merritt, 1989, ApJ, 343, 617}

		%    {}

\ReferencePair

{F. Bournaud, B.C. Elmegreen, D.M. Elmegreen, 2007, ApJ, 670, 237}

{K. Kraljic, F. Bournaud, M. Martig, 2012, ApJ, 757, Aid60}

\ReferencePair

{S. Barway, Y. Wadadekar, A.K. Kembhavi, Y.D. Mayya, 2009, MNRAS, 394, 1991}

{S. van den Bergh, 1990, ApJ, 348, 57}

\ReferencePair

{H. Butcher, A. Oemler Jr., 1978, ApJ, 219, 18}

{H. Butcher, A. Oemler Jr., 1978, ApJ, 226, 559}

\ReferencePair

{L.C. Prochaska Chamberlain, et al., 2011, MNRAS, 412, 423}

{J.C. Roediger, S. Courteau, L.A. MacArthur, M. McDonald, 2011,

MNRAS, 416, 1996}

\ReferencePair

{ G. Fasano, et al., 2000, ApJ,  542,  673}

{O.K. Sil'chenko, I.S. Proshina, A.P. Shulga, S.E. Koposov, 2012, MNRAS, 427, 790}

\ReferencePair

{Kniazev et al. 2005, AJ, 130, 1558}

{Kniazev et al. 2008, MNRAS, 388, 1667}

\ReferencePair

{Kniazev et al. 2004b, ApJS, 153, 429}

{Katkov, Kniazev, Silchenko 2014, in preparation}

\ReferencePair

{Chilingarian et al. 2007, IAU Symposium, V.241, 175-176}

{Kniazev \& Sil'chenko, 2012, SALT report 2202AA0001}

\ReferencePair

{Sil'chenko O. 2013, MSAIS, 25, 93}

{Johnston E.J., Aragon-Salamanca A., Merrifield M.R. 2014, MNRAS, 441, 333}

}

	

	\AdditionalFigures{

		% Insert any additional figures and graphics here.

		%

		% Allowable file types are:

		% If you are compiling using PDFLaTeX: JPG, PNG, PDF, EPS

		% If you are compiling with plain LaTeX: EPS only

		%

		% Example:

		% \includegraphics[height=200px]{Filename.eps}

\vbox{

\begin{center}

    \includegraphics[clip=,angle=-0,width=5.0cm]{F9.medium.ps}

    \includegraphics[clip=,angle=-0,width=6.0cm]{plot_ages.ps}



{{\bf Fig\,1:}

The comparison of the obtained SSP-equivalent ages of the discs and bulges in our samples of S0s.

The equality straight line is plotted for the reference.

{\it Left panel:} Results from Sil'chenko et al. (2012) for a sample of nearby

S0s in loose groups;

{\it Right panel:} Results from Katkov, Kniazev \& Sil'chenko (2014) for a sample

of completely isolated S0s.

}

\end{center}

}

\vbox{

\begin{center}

    \includegraphics[clip=,angle=-0,width=6.0cm]{plot_mgfes.eps}

    \includegraphics[clip=,angle=-0,width=5.0cm]{age_corr.eps}



{{\bf Fig\,2:}

{\it Left panel:} The comparison of Mg/Fe ratio in the bulges and in the disc structures

(could be found {\bf ONLY} with Lick indices method)

for S0 galaxies from Katkov, Kniazev \& Silchenko (2014).

{\it Right panel:} The comparison of bulges ages defined with both methods:

Lick indices and NBursts package (Katkov, Kniazev \& Silchenko, 2014).

}

\end{center}

}

	}

	

\end{document}