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					     PROBING EVOLUTIONARY
   MECHANISMS IN GALAXIES OF
    NEARBY CLUSTERS WITH HI


Tom Scott
University of Hertfordshire
UK


Supervisors:
 Elias Brinks
 Hector Bravo - Alfaro
 Martin Hardcastle
              OUTLINE
• Galaxy Clusters
  – Components
  – Spiral galaxies
     • HI observed correlations
     • HI removal mechanisms


• Project
  – A1367
     • VLA observations
     • Initial HI detections


• Future Work
          CLUSTER COMPONENTS
W         Wm *
L = 0.7
                            Galaxy types:

M = 0.3   DM       = 0.26      Early (E+S0) - old stars, no gas

                               Late (Sa + later) - disks and bulges of
          ICM      = 0.03      stars, plus bound gas


          Galaxies = 0.01
                               ICM = Inter Cluster medium - x-ray emitting gas
          (stars and gas
          bound to
          galaxies [ISM])

                               * = Based on L CDM model + Virgo observations Evrard 2004
 RELATION CLUSTER COMPONENTS




                                                                  Z = 0.3



• Dark Matter Gas and Stellar components
     Mass (DM) profile from Gravitational lens merging cluster 1E0657-558
     Galaxy Clusters
  of Optical galaxies (Stellar light)          Colour ICM gas X-ray
                                              Clowe et al. 2006
            CLUSTER GALAXIES -
         OBSERVATED CORELATIONS
   Morphology Density Relation (z = 0)



• Fraction early type (E+SO) is
  positively correlated to galaxy

                                    Fraction of galaxies
  density (Dressler 1980)




                                                           Density

                                                                     SAO encyclopaedia
             CLUSTER SPIRALS –
           STAR FORMATION RATES

• Fraction of optically blue (star
  forming) galaxies in clusters
  increases z =0 - 0.4 (Butcher
  Oemler 1984)




                                     Fraction of blue galaxies
                                                                 Fraction of Blue
• Possibly higher star formation                                 Galaxies as function
                                                                 of z
  rates a higher z arise from
  higher rates of galaxy
  accretion during cluster
  formation?

                                                                    Redshift
                                     Fraction of blue galaxies in the magnitude range between M* - 1 and
                                     M* + 2 and within 0.7 Mpc from cluster centre.
                                     ZSP =spectroscopic ZPH =photometric redshifts. Margoniner 2001
                    CLUSTER SPIRALS -
                           HI
Normal spirals - HI gas disk radius ~




                                                               Fraction of spirals with
                                                               Fraction of spirals with
1.8 x optical disk                                                                                           FRACTION
                                                                                                             GALAXIES
Approaching cluster core:                                                                                    WITH HI
                                                                                                             DEFICIENCY




                                                               DEF > 0.3
 – % HI deficient galaxies increases
 – Amount of deficiency increases
 – % with truncated HI disks increases
                                                                                                               HI
 Other correlations                                                                                            DEFICIENCY




                                               HI deficiency
                                                                               -
 – Reduced star formation rates correlate to
                                                                               -
   HI deficiency                                                               -
 – Radio continuum excess in HI deficient                                      .
   galaxies
 – HI deficiency correlates with x-ray
   luminosity (~ICM density)                                                                            R/RA
 – HI deficient galaxies have more radial                          Top Fraction of HI deficient galaxies as a function of distance from the
   orbits                                                          cluster core. Bottom deficiency for the HI deficient fraction
                                                                   RA = Abell Radius (Solanes 2001)
           HI REMOVAL MECHANISIMS
                                                                       Blue Infall Group A1367R band image
•   Gravitational interactions                                         Gavazzi 2003

     –   Cluster potential as whole
     –   Galaxy-galaxy interactions
           SLOW interactions
           • Gas removal needs low speed encounters - groups
           • Triggers increased star formation - especially nuclear
           • Stellar shells

           FAST interactions
           • Harassment (multiple fast encounters) several x 108 yrs

•   Hydrodynamic ICM / ISM interactions                                Shell implies gravitational encounter



     –   Ram pressure stripping -108 yr
     –   Viscous stripping
     –   Thermal evaporation
     –   Starvation

•   Ram Pressure Stripping natural explanation HI
    deficiency and it correlations

•   Does not explain increase in S0 fraction with density
                                                                        Gray-scale = stellar disk
                                                                        (Optical)
                                                                        Contours = HI Truncated HI disk, morphology and HI
                                                                                      velocities imply Ram Pressure
                                                                        (radio)
                                                                                      stripping
                    CLUSTERS –
                  HI OBSEVATIONS
– HI hard to detect - sensitivity and spatial resolution

– Single dish (e.g. Arecibo 300m) sensitive, very poor resolution ~
  3.2 arcmin.

– Interferometers (e.g. VLA) spatial resolution (D configuration 45”)
  allows observation of HI distribution within galaxies, but less
  sensitive

– Asymmetric HI distribution in disk implies recent disturbance
    • differential rotation will smear out within 108 yrs
         – Implies recent interaction
             » Infall
             » Approach cluster core
             » Gravitational encounter.
PROJECT – INTERFEROMETRIC HI
 SPECTRAL LINE OBSEVATIONS
Probe evolutionary mechanisms in cluster spirals

    – Initial Low z - VLA data

        • Abell1367 (z = 0.02)
        • Abell 85 (z = 0.05)

    – Extend observations to higher z
             – Abell 1689 (z = 0.18)
             – Abell 2667 (z =0.23) – GMRT time allocated

    – IRAM 30m single dish molecular gas observations
        • Proposal in preparation for selected A1367 galaxies
    A1367 - SPIRAL RICH CLUSTER
Cluster forming at intersection of filaments joining Virgo and Coma
  Clusters

•   Dynamically young and spiral rich
•   X- ray identified two major subclusters (NW & SE ) with temperature jump
    suggests merger shock (Donnelly 1998)


• NW sub-cluster early stage merger with main SE sub-cluster

                                                                 NW SUBCLUSTER




                           X-ray contours ROSAT
                           galaxy iso density contours
                                        (Cortese 2004)
                                                 SE SUBCLUSTER
A1367 VELOCITY
SUBSTRUCTURE
Radial velocities (Optical )
                                                                                 SE                  NW
       - NW near Gaussian distribution
       - SE far from Gaussian => multiple in-
       fall groups                                                                         6400 kms -1     6900 kms -1
                                                                                           main relaxed    infall sub
                                                5500 kms -1       6500 kms -1              group           cluster
                                                low velocity      main relaxed
                                                group             group
                                                                                                     A1367 (Cortese 2004)




                        ALL A1367                                    SE SUBCLUSTER                 NW SUBCLUSTER



                                                                           8200 kms -1
                                                                           high velocity
                                                                           group




A1367 LOS velocity distributions Total and sub-clusters (Cortese 2004)
    NW SUB-CLUSTER- VLA CUBES (2)
A1367 galaxies within FOVs (42 arc min diameter) and velocity range


                                                     Blue Infall
                                                     Group
Cubes:
Centered NW sub cluster
velocity range
(5,677 – 7875 kms-1)      -
AB 900

Periphery NW sub cluster
(7,957 – 8544 kms-1)     -
AH801
                  A1367 - INITIAL RESULTS
                                                        Filament toward
                                                        Coma Cluster
NW & W
                                          97-068
SUBCLUSTERS
HI moment 0 contours
                              97-079
Image POSSII b   97-091                              9 HI detections
                                                           3 starburst,
                                        97-073
                                                           4 late type
                                                           2 dwarfs)
                          97-087

                                                     Concentrated in the
                                                     W subcluster

                                                   NW SUBCLUSTER



                           [GP82]1227
                                                                      W SUBCLUSTER
                             A1367 - EXAMPLES

HI DETECTIONS - AB900 Cube


Top Colour contours = HI moment 0 contours. image = POSSII Blue,   Below SDSS DR6 images
           97-087                    97-073                        97-079                  A1367[GP82]1227




                            a
97-087




         INTERGRATED HI FLUX
         VELOCITY FIELD - AGES
         HI mass ~7.2 x 109 Msolar
         HI def ~ 0.23
                         NEXT STEPS

•   Cluster spirals within A 1367 FOV s

     – Detected galaxies
        • HI distribution / mass / kinematics
        • relate to other wavelengths, e.g. star formation indicators

     – non detections
        • gas mass upper limits

•   Average HI spectra from Arecibo AGES / optical spiral galaxy positions
     – Low z
        • Increase sensitivity to lower <MHI> ~ factor 10 improvement (Chengalur 2001)
        • Mean HI in sub structures
     – Higher z
        • Increase detection sensitivity

•   Investigate mass loss mechanisms by comparing observations / models

				
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posted:10/11/2011
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