Ste llar P opulations at intermediate redshift S urvey w ith WEAVE Bianca Poggianti Angela Iovino co Leads o n behalf of the StePS team A Mercurio M ID: 561431
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Slide1
StePS
Stellar Populations at intermediate redshift Surveywith WEAVE
Bianca Poggianti – Angela Iovino (co-Leads)on behalf of the StePS team A. Mercurio, M. Longhetti, L. Morelli, L. Pozzetti, A. Gallazzi, M. Bolzonella, S. Zibetti, C. Haines , S. Trager, M. Balcells, I. Ferreras, J. Gallego, R. Garcia Benito, R. Gonzales-Delgado, J. Iglesia, J. Iglesias Paramo, J. Knapen, A. Pizzella, S. McGee, P. Sanchez Blazquez, C. Weidner, P. Merluzzi, G. Busarello, N. Napolitano, F. La Barbera, E. Zucca, S. BardelliSlide2
StePS
motivation
Studies of galaxy evolution based on an “archaelogical” approach (stellar populations of present-day galaxies to infer the galaxy history – e.g. SDSS), or observing galaxies at earlier epochs (mainly snapshots of their evolution, eg. large spectroscopic surveys such as zCOSMOS, VIPERS).Application of archaelogical approach at different epochs a significant step forward. Slide3
NEED FOR GOOD
S
/N and resolution
Our and others’ simulations show that S/N>15 needed to do detailed stellar population analysis (stellar ages, metallicities, sigma, dust with 10% accuracy or better)Citro, Pozzetti et al. 2016Stacking is poor substitute because high quality individual spectra crucial fordescription of any statistical distribution of physical properties beyond the averagequantifying the amount of stochasticity involved in galaxy evolution processes understand the time-scales of transitional phases. Slide4
NEED FOR GOOD
S
/N and resolution
As of today, spectroscopic studies with sufficient S/N and resolution at intermediate redshift have been limited to relatively small samples of galaxies or to co-added spectra. Examples: BOSS typical S/N 3-5 per 69km/s (rebinned) pixelLega-C (VLT) 2700 galaxies at z=0.6-1 (but StePS >10X number of galaxies, complementary redshift range and possibility to address environmental issues)VIPERS (dashed) vs SDSS (solid coloured) and model (solid black) spectraSlide5
WEAVE can do
it
thanks to:
Large FoV Good resolution (R~5800) over a wide wavelength range (3700-9500Å) Excellent multiplexing Slide6
Tracing back in cosmic time the evolution
of galaxy stellar population properties
as a function of galaxy stellar mass and environment, to understand the physical mechanisms that regulate galaxy formation and assembly history. StePs will extend the SDSS results to a baseline encompassing the last 7 Gyr of cosmic time
StePS science goal: Slide7
StePS is a spectroscopic survey of ~
30K galaxies
magnitude brighter than IAB =20.5pre-selected from photometric redshifts to be at z > 0.3
(except in the COSMOS field) – redshift range 0.3-0.7: an epoch when galaxies are quickly evolving and SFR drops by a factor of 2At least 100 galaxies in:4 bins of galaxy masses4 bins of color5 bins of environment4 bins of cosmic epochsLog mass limits:z=0.3 10.2z=0.5 11.0z=0.7 11.3StePS
in a
nutshell
I Slide8
LR mode (
R=5000)
For each galaxy S/N
per resolution element >15 to study: stellar ages, star formation and star formation histories, stellar and gas metallicities, dust attenuation, stellar velocity dispersions and gas kinematics and their relation with the intrinsic (galaxy stellar mass, morphology/color/size) and environmental properties.StePS in a nutshell IITHIS REQUIRES EXPOSURE TIMES OF 7 HOURS PER GALAXY (14 HOURS FOR THE REDDEST SUBSET, 20% of the targets) – This sets StePS apart from the other WEAVE surveys for the requirement of completion of long exposure on each galaxyMultipass strategy of 5 passes (5passesX7hours/tile) + 10 passes in COSMOS65% sampling rate, except in COSMOS 80%Slide9
On a
relatively wide area: 25 deg^2
StePS in a nutshell III
✖✖✖✖Why:excellent optical+nearIR data, reliable photo-zwell sampled spectroscopic data to characterize environmentextra ancillary data to define environment (eg X-ray), galaxy structure (HST) etcSlide10
StePS
will
carry out a detailed analysis of:Stellar
ages and metallicitiesStellar massesStar formation rates and historiesGas metallicities, electron density, ionization parameterDust attenuation
Stellar
velocity
dispersion
Gas
kinematics
Galaxy
dynamical
masses
Gas
outflows
…
via
--
absorption
-line
spectral
indices
(
optical
and UV)
-- full
spectral
fitting
--
emission
-line
measurements
StePS
in a
nutshell
IV Slide11
Extra sample in COSMOS with no photo-
z
preselection yields 2.2k galaxies with z<0.3 to:
extend to lower masses tha analysis done by SDSSperform spectral analysis at rest frame lambda > 8000 A for IMF
determination
in
early-type
galaxies
StePS
in a
nutshell
V Slide12
StePS
UNIQUENESS StePS will be the first survey to provide:the necessary spectral quality for a large sample of galaxies at z=0.3-0.7
to obtain an accurate estimate of all main stellar population characteristics, stellar velocity dispersions, gas metallicity and kinematics andtheir relations with galaxy stellar mass + other intrinsic properties (type, color) and environment over a significant interval of cosmic time.Slide13
OPENING POST-DOC POSITION
IN ITALY FOR STEPSSlide14
THANKS!!