Constraints on feedback from deep field observations with sauron and vimos
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Constraints on feedback from deep field observations with SAURON and VIMOS. IFU observations of the high-z Universe. Joris Gerssen. Overview. Until a decade ago only extreme objects were known in the distant universe

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IFU observations of the high-z Universe

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Constraints on feedback from deep field observations with SAURON and VIMOS

IFU observations of the high-z Universe

Joris Gerssen


  • 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.

  • 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

Integral Field Spectroscopy

Data cube: f(x, y, lambda)



  • MUSE


  • PMAS

Typical properties:

Field-of-View few (tens) of arcsec

Spectral resolution: R ~200 to ~2500

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

    • ...


  • A longstanding problem in galaxy formation is to understand how gas cools to form galaxies

  • Discrepancy between observed baryon fraction (~8%) and predicted fraction (> 50% )

  • To solve this “cosmic cooling crisis” the cooling of gas needs to be balanced by the injection of energy (SNe/AGN)


  • 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)

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

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

SAURON observations: overview





SSA22b (z = 3.09)

Wilman, Gerssen, Bower, Morris, Bacon, de Zeeuw & Davies (Nature, 14 July 2005)

VolView rendering

Ly- distribution

1.0 arcsec = 7.6 kpc

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

Model cartoon

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

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)

SINFONI observations of SSA22b

Constrain the stellar properties

Link them to the superwind

Scheduled for P77 (B)

Foerster Schreiber et al.

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

Mean IGM transmission

z ~ 2.5

z ~ 3

Adelberger et al. 2003

Adelberger et al. 2005

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

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 +1738+350


z = 3.92, Texp = 9 hours

LR mode

Search by eye for candidates

Need to identify/apply an automated procedure

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)

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

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)

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


  • 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

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