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Minutes for the VIRMOS-VLT deep survey meeting in Porquerolles, 6th, 7th October 2005
by HJMCC - Updated February 24th, 2006

VIRMOS VLT deep survey science meeting in Poquerolles, France

6th-7th October 2005

Present: Isabelle Gavignaud, Alain Mazure, Lydia Tasca, Stephane Arnouts, Thierry Contini, Stephane Palatani, Marco Scogdeggio, Paolo Franzetti, Jarle Brinchmann (first day), Olivier Ilbert, Baptiste Meneux, Laurence Tresse, Olga Cuciatti, Agnieszka Pollo, Angela Iovino, Alberto Cappi, Micol Bolzonella, Angela Bongiorno, Henry McCracken, Robert Scaramella, Fabrice Lamareille, Bianca Garilli, Dario Macaggani, Daneila Vergani, Christian Marinoni (second day only)

Schedule distributed by Olivier before the meeting


-  Henry is going to distribute a summary of what imaging is already available on the fields and the quality of the images available.

-  Henry: It was pointed out that the old headers in the F02 images were corrupted, which may be causing problems with some software packages: He will provide corrected version to Vincent

-  Vincent,OLF: Need to identify at the database level how to identify objects whose redshift has changed.

-  Marco: Need see how VIPGI can be adapted to reduce FORS2 data

First day, 6th of October

Latest news (OLF, presentation)

-  In the last few weeks, most people have been occupied by the preparation of new proposals for September deadline

-  The main challenge now is to finish the epoch-II data reductions

-  36 pointings to be reduced

-  Two processing sessions have taken place in Bologna and Marseille which were a bit different as the reducers stayed at their home sites

-  In the F22 field there is 4 deg2 covered with VIMOS and there are 7 pointings ready to be integrated in the database VDS

-  Still ten pointings to do reduce on the F22 field, which probably means two more reduction sessions

-  Twenty pointings in total over all fields still to do which probably means five super-check sessions.

-  The dates of several super-check sessions were defined by OLF, see attached presentation.

SINFONI proposal (Thierry et al, presentation

-  The object of this proposal is to find out about physical processes in intermediate-to-high redshift star-forming galaxies at 1.4-  4 nights successfully executed
-  F02/F22 galaxies selected with secure redshifts which avoid bright OH sky lines
-  10 of 12 galaxies successfully observed!
-  Most of these objects are at z 1.5, although there are two objects at 3.2
-  Enough lines are present in many objects to get physical parameters, and to look at H-alpha kinematics
-  Proposal resubmitted for the next observing session

Z-tools (Frazetti et al, presentation)
-  Introducing, EZ, an automatic redshift measurement tool
-  This tool will build on scientific and software expertise gained from reducing thousands of spectra with the previous generation tools
-  The tool is designed to work with any instrument.
-  The aim is to get 50% correct-z, 30% within 0.1 and 20% to be inspected, which is more or less what we have already
-  Software will be written in python with algorithms coded in C for speed.
-  Prototype code already tested which allows processing of spectrum and obtains a redshift measurement
-  Can visually inspect best fitting template
-  Hope to distribute this prototype to the VVDS community before the end of the year.
-  Stephane Palatani insists that the code should be tested on 'real' spectra and not simulations; it's easy to get good results with simulations
-  Software has not been tested extensively tested yet on the VIMOS LR-BLUE configuration.
-  Some news about VIPGI; can overplot spectra and shift templates around.

LR-BLUE observations with VIMOS (OLF, presentation)

-  One pointing has been acquired in DDT (Director's discretionary time) with a 4.5hrs integration

-  A second pointing is in progress (pre-imaging has been acquired) and spectra should be taken before the end of the year
-  120 objects per quadrant have been observed
-  From the DDT data, two quadrants have been reduced and z-measurements are in progress
-  Combined spectrum shown using LRED+LRBLUE, this object goes from flag->1 to flag->2; redshift didn't change

K-band observations (Angela no presentation)

-  BEFORE there was 9 SOFI pointings covering 170arcmin2 in the F02 field
-  NOW have 700arcmin2 over the region with four passes.
-  Now we should have 1000 galaxies to K 19.5 with spectra already available free from selection effects
-  Only observations in K

High redshift cluster proposal, Angela, no presentation

-  Only half of time requested was awarded
-  Three classes of objects observed in integrations of 3.hrs, 6hrs and 9hrs for the super-faint sample
-  60 objects preselected using phot-zeds
-  Should have a success rate 60%
-  Hopefully we will get 15-20 spectra in the cluster
-  Dario suggests preparing an XMM proposal to target the cluster, but it is not clear that such a proposal could be justified.

QSOs, Isabelle

-  Two nights coming up with visitor mode in FORS in November to observe quasars with LRBLUE
-  38 objects will be observed with up to 1hr integration.
-  The remaining slits will be selected by the spectrophotometric group
-  OLF suggests we try to think about other programs which can be targetted with one hour integration on FORS-1

Submitted proposals P77 (Olivier, presentation)

-  Two VVDS VIMOS proposals resubmitted as large programs
-  One will to go super-deep in LR-BLUE and LR-RED
-  The other is Gigi's 'wide' proposal
-  SINFONI proposal for four nights submitted
-  FORS-1 on AGNS submitted by Vincent to examine damped Lyman-alpha systems (Olivier reminds us that there some objects which have spectra containing absorption lines which cannot be explained)
-  CFHT-WIRCAM JHK proposal targetting in F02/Cosmos field
-  Also Cuby et al proposal emission line proposal
-  Also WFCAM (UKIRT) data, not sure about the status of this

Public data release (OLF, Presentation)

-  Theirry, Bianca, Fabrice, Paolo will have a telecon to try to decide how to proceed with the data release, and which spectra need cleaning
-  First epoch data was taken in 2002; we should make the data public!
-  How much work will be required to make this data release acceptable to the community? Do we need to clean spectra?
-  OLF suggests tentative date of May 2006
-  Do we need to release the spectra or just the redshift?
-  OLF suggests release redshifts, quality flags as a baseline.

Science Presentations

VVDS Summary (OLF, presentation)

-  Tenth anniversary! Only six people present at the meeting today were present ten years previously
-  1995 This 'crack team' of six were comissioned by ESO to produce a phase-A document for a next-generation spectroscopic instrument
-  OLF reviewed the main points of VVDS and the most important scientific results
-  Financial cost of VIMOS-VVDS outlined

Summary of ten years of VVDS software (Bianca, presentation)
-  VIMOS control software
-  DRS/VIPGI (and derived products)
-  This software has been extensively tested.
-  Also a long list of other software like Hyper-Z , LF tools...
-  Suggestion to make a complete toolbox revived

Luminosity densities and luminosity evolution (Laurence, presentation)
-  Summary of VVDS work in the luminosity function
-  List of papers submitted and in press described
-  LF by density, K-band LF from SWIRE
-  VVDS goes 1.5 times fainter than CFRS and can better constrain the evolution as a function of redshift thanks to the wide range of redshifts probed
-  Results for evolution of luminosity density as a function of redshift presented
-  For the first time we are able to determine the emissivity in different bands
-  Also show evolution of "nearly normal galaxies" and the evolution of LF and LD by type (from Elena)
-  Luminosity densities and LF evolution at 1500AA and 2800AA.
-  Luminosity densities derived over various ranges in absolute luminosity

Photometric redshift and LFs (Olivier Ilbert, presentation)
-  Photometric redshifts now seem to work well
-  phot-zeds agree well with the spec-zeds, the problem of systematic errors and been (mostly) solved
-  The big problem is that there are still some catastrophic errors in which the balmer break and lyman break are confused, the only way to get rid of this would be to introduce a prior? Perhaps on the size of galaxies?
-  The LF computed by phot-zeds seems to be have a higher M* than the photometric sample
-  OLF suggests that the best approach with with the phot-zeds data is to publish the scientific papers BEFORE the paper describing the zphot method

Galaxy clustering in the CFHTLS with photzeds (Henry, presentation)

-  Henry shows results on galaxy clustering by type and redshifts derived from the CFHTLS photometric redshifts
-  can recover the VVDS r0 as a function of redshift with the CFHTLS fields
-  results for evolution of r0 for absolute luminosity which shows a decline in r0 as a function of redshift.

SWIRE (Stephane Arnouts, presentation)
-  Colour-colour diagrams for z>1 r-i vs i-m36
-  redshift distribution for flag 0 objects presented
-  flag-1 objects are 50% wrong and 80% are in the z>1 region
-  for the flag-2 objects, 20% are wrong and 56% in z>1 region
-  LF from K/SWIRE sample at 3.5 and 4.5 and LF is the same at all redshifts
-  LF by type for the K/SWIRE sample
-  Evolution of phistar for early types to redshift 2.5 for the first time!
-  Luminosity density from SWIRE data derived
-  Omega* from the Luminosity density; we see a decline omega* as a function of redshift

Clustering evolution, presentation (Olivier)
-  OLF makes a summary because Gigi couldn't be present due to illness

Luminosity dependent correlations (Agnieszka, presentation)
-  make two broad samples in limited in absolute magnitude
-  Look at the variation in absolute luminosity as a function of r0 at a give redshift bin.
-  Can derive the evolution of the slope of the correlation function (gamma) as a function of luminosity than
-  Also derives the relative bias as a function of luminosity in two redshift bins

Correlation function (Baptiste, presentation)

-  Global correlation function paper
-  Evolution of r0 as a function of type for magnitude limited samples.
-  Rest-frame colour distribution (bimodality)
-  Define blue and red sample up to z=1.2
-  Also look at the the clustering evolution of UV selected samples using GALEX

...followed by a cocktail, the Virmos-VLT tenth anniversary dinner, champagne and a presentation from Olivier describing the last ten years of virmos....

Second day

OII/Halpha/velocity relation (Christian, presentation)

-  The question to address is if o-ii can be used at high-redshift like h-alpha at low redshift and to address the zero-point of this relation at low redshift
-  32 spirals used to derive the relation between OII line width versus rotation derived from H-alpha

-  It was not clear if there was really a relation, or if it was just a selection effect

Colour distribution as a function of environment (Olga Cucciati, presentation)
-  local density field computed
-  (U-R) vs R as a function of environment for a range of redshifts and environment
-  No difference between low and and high density environment
-  Colour fraction as a function of local density, surprising result is that the red galaxies have little dependence for the red population.
-  One important effect which has to be accounted for is luminosity selection effects

Bimodalty (Paolo Franzetti, presentation)
-  Try to compare with other work (Bell), and to develop quantative estimates for bimodality
-  There is a systematic offsets between OI colours and PF colours which we don't really understand
-  Try to use the KMM code from Ashman et al to quantify the amount of bimodality present in the data
-  Still need to decide what the best cut is! Considerable discussion followed once more.
-  See section on red galaxies for a more physically motivated bimodal cut
-  How can we proceed? One suggestion is to look at the distribution of objects in three-parameter space (U-B), (B-V) and V

Cosmological evolution of physical properties of galaxies (Theirry, presentation)
-  Surveys at higher redshift lower spectral resolution
-  List of physical parameters which can be derived as a function of redshifts
-  Platefit has been applied on around 6000 spectra
-  A spectrophotometric catalogue has been released containing emission line measurements and stellar continuum measurements
-  Spectrophotometric analysis can now start!
-  Theirry outlined many papers which are possible with this dataset

Spectrophotometry (Fabrice, Presentation)
-  spectrophotometric observations fitted to Bruzal-charlot models
-  Stellar masses derived
-  SFR rates derived
-  Metallicities derived; this parameter is less well constrained
-  Can look at the evolution of the specific star formation rate as a function of mass and redshift.
-  Internal data release 0.1b contains 5977 galaxies.
-  Strength of the D4000 break seems to be lower in the VVDS than other surveys

Reddest galaxies in the VVDS (OLF, presentation)
-  Summed-up spectra of the VVDS and then platefit software used to derive physical parameters
-  Not as deep a other surveys, but because we have a large area we get very red objects, brighter objects.

Reddest objects in the VVDS (Daniela Vergani)
-  Examine differences between reddest galaxies selected in two different ways
-  B/C models
-  LF approach
-  No significant differences between VVDS between faint and bright reddest objects
-  OLF insists the D4000 vs OII method is a good way to separate galaxy populations rather than drawing arbitrary lines in colour-magnitude space, and that this method could be very useful for the bimodality studies
-  Stephane arnouts and Olivier Ilbert are going to try this method
-  No evidence for the evolution of the strength of the D4000 feature.
-  Some differences with the stacked templates from OLF at high redshift (DV sample seems to contain emission line objects)

Mass function (Micol, who presented the MF paper)
-  Mass functions derived from the masses from Fabrice
-  Compared with k-20, combo-17, cole et al.
-  Seem to be consistent with k=20
-  i-selected masses
-  up to redshift 1 the mass function is constant
-  above redshift 1 there is an evolution in MF
-  VVDS provides better constraints on the low mass end of the MF

AGN, Isabelle (Presentation)
-  130 AGNs now
-  250 with all available data.
-  number counts
-  the mean redshift of the sample doesn't depend on limiting magnitudes
-  24% AGNs are extended at low redshift
-  investigation of distribution of VVDS objects in traditional quasar selection criteria; many VVDS objects would not be selected by traditional colour-magnitude cuts
-  excess of low luminosity AGNs at z 1

Multi-colour analysis (Olivier, presentation)
-  ugrizBVRIK from CFHT/NTT
-  data from far UV to X-rays, radio
-  galex 1500 VVDS redshifts
-  spitzer-swire, 3000 redshifts, 3.6 microns selection
-  250 redshifts at 24 microns
-  radio sources, XMM sources: a new approach is to make image sums to get average properties of galaxies

Characterisation of x-ray properties of unclassified sources (Bianca, presentation)
-  stack x-ray images to see if there are any detections below the official '4 sigma' catalogue (images are not actually stacked because photon lists are coadded)
-  technique seems promising, but there are a few technical issues to resolve

Final session (Olivier, presentation)

Priorities and papers in press (Olivier, presentation)
-  list 20 papers in press or at refereeing stage presented
-  list of papers in preparation presented
-  2nd, 3rd February: Next VIRMOS science meeting: Paris, city of lights!

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