IFU observations of the high-z Universe

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IFU observations of the high-z Universe

• Constraints on feedback from deep field
  observations with SAURON and VIMOS

Joris Gerssen
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Overview

• Until a decade ago only extreme objects were
  known in the distant universe
• Since then photometric redshift surveys and
  narrow band surveys identified ( at z 2 to 4)
• Lyman Break Galaxies
• Ly-alpha galaxies
• Observational constraints on galaxy formation and
  evolution
• e.g. morphology, star formation history,
  luminosty functions, etc.

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• Among the drivers behind this advancement are
• The 10m class telescopes and instruments
• Hubble Space Telescope
• Theoretical understanding of structure formation
• Integral Field Spectropscopy (IFS) is a recent
  development with great potential to further
  galaxy evolution studies

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Integral Field Spectroscopy
Data cube f(x, y, lambda)

• VIMOS
• SINFONI
• MUSE
• SAURON
• PMAS

Typical properties
Field-of-View few (tens) of arcsec
Spectral resolution R 200 to 2500
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High-redshift science with IFUs

• (e.g. list of MUSE science drivers)
• Formation and evolution of galaxies
• High-z Ly-? emitters
• Feedback
• Luminosity functions (PPAK, VIRUS)
• Reionization
• ...

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Feedback

• A longstanding problem in galaxy formation is to
  understand how gas cools to form galaxies
• Discrepancy between observed baryon fraction
  (8) and predicted fraction (gt 50 )
• To solve this cosmic cooling crisis the cooling
  of gas needs to be balanced by the injection of
  energy (SNe/AGN)

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Feedback

• Galactic outflows driven by AGN and/or SNe
• Resolve discrepancy between observed and
  predicted baryon fraction
• Terminate star formation
• Enrich IGM

NGC 6240 (ULIRG)
M82 (starburst)
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IFU Deep Field Observations

• Deep SAURON VIMOS observations of blank sky
• But in practice centered on QSOs/high-z galaxies
• observe extended Ly-? halo emission
• serendipitous detections

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SAURON Deep Fields

• The SAURON IFU is optimized for the study of
  internal kinematics in early type galaxies
• DF observations of SSA22a, SSA22b, HB89
• Redshift range 2.9 - 3.3 (4900 - 5400 Angstrom)
• Texp 10 hours
• FoV 33 x 41 arcsec, R 1500

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SAURON observations overview
SSA22a
SSA22b
HB89 1738350
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SSA22b (z 3.09)
Wilman, Gerssen, Bower, Morris, Bacon, de Zeeuw
Davies (Nature, 14 July 2005)
VolView rendering
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Ly-? distribution
1.0 arcsec 7.6 kpc
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Line profiles

• Emission lines 1000 km/s wide
• Emission peaks shift by a few 100 km/s
• Absorption minima differ by at most a few tens of
  km/s
• Ly alpha is resonant scattered, naturally double
  peaked
• Yet, absorption by neutral gas is a more
  straighforward explanation

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Model cartoon
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SSA22b results

• Assuming shock velocities of several 100 km/s
• Shell travels 100 kpc in a few 108yr
• Shell can cool to 104 K in this time
• Implied by the Voigt profile b parameter
• Required to be in photoionization equilibrium
• Implied shell mass of 1011 M?
• Kinetic energy of the shell 1058 erg
• About 1060 erg available (IMF)
• Superwind model provides a consistent, and
  energetically feasible description

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Comparison with SSA22a

• SSA22a
• Kinematical structure more irregular
• Luminous sub-mm source
• Suggests that a similar outflow may have just
  begun
• Probe a wider range of galaxies
• SCUBA galaxy (observed last year)
• Radio galaxy (observed one last week)
• LBG (a few hours last week)

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SINFONI observations of SSA22b
Constrain the stellar properties Link them to the
superwind Scheduled for P77 (B)
Foerster Schreiber et al.
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Serendipitous emitters

• The correlation of Ly-alpha emitters with the
  distribution of intergalactic gas provides
  another route to observationally constrain
  feedback
• Based on Adelberger et al (2003) who find that
  the mean transmission increases close to a QSO
• This result is derived from 3 Ly-? sources only

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Mean IGM transmission
z 2.5
z 3
Adelberger et al. 2003
Adelberger et al. 2005
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Advantage of IFUs

• IFUs cover a smaller FOV then narrow band
  imaging, but
• IFUs are better matched to Ly-alpha line width
• Do not require spectroscopic follow-up
• Directly probe the volume around a central QSO
• Thus, IFUs should be more efficient than narrow
  band surveys

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IFU observations

• Search the data cube for emitters
• Use the QSO spectrum to measure the gas
  distribution
• Likely require the UVES spectra
• Available
• One SAURON data cube
• 2 of 4 VIMOS IFU data cubes

SAURON example HB89 1738350
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VIMOS 'QSO2'
z 3.92, Texp 9 hours LR mode
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Search by eye for candidates
Need to identify/apply an automated procedure
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Detection algorithms

• Matched kernel search
• Many false detections
• IDL algorithm (van Breukelen Jarvis 2005)
• FLEX X-ray based technique (Braito et al. 2005)
• ELISE-3D sextractor based (Foucaud 2005)

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van Breukelen Jarvis (MNRAS 2005)

• Similar data set
• Radio galaxy at z 2.9
• same instrumental set up
• similar exposure time
• Yet, they find more (14) and brighter Ly-?
  emitters
• Using an automated source finder

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In progress

• A direct comparison with the van Breukelen
  results
• Obtained their data from ESO archive
• And reduced and analyzed it with our procedures
• Preliminary results are in reasonably good
  agreement
• Our data appears somwhat more noisy
• Find their emitters and their new type-II quasar
  (Jarvis et al 2005)

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Preliminary results

• Number density of Ly alpha emitters agrees with
  model predictions (fortuitous)
• The VIMOS fields contain 5 - 14 emitters
• Models (Deliou 2005) predict 9 in a similar
  volume
• IFUs are sensitive to at least a few 10E-18
  erg/s/cm2

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Summary

• IFUs provide a uniquely powerful way to study the
  haloes around high redshift proto-galaxies
• Volumetric data are an efficient way to search
  for Ly-alpha galaxies
• An alternative method to constrain feedback
• IFUs are a very valuable new tool to study the
  formation and evolution of galaxies