6dF Galaxy Survey Work Shop K. Wakamatsu (Gifu University) Redshift Survey near the Galactic Plane with 6dF

How deep can we penetrate into the Galactic Plane for the redshift Survey? An Example for the Galactic Center Region: Ophiuchus cluster

Discovered on Palomar Schmidt IV-N Plates during Hidden Globular Cluster Survey l=0.5° b=+9.3 °(Near the Galactic Center) A B =2.5 mag Nearby rich cD cluster (V=8400 km/s) The 2 nd brightest X-Ray cluster after Perseus cluster May be a Key cluster for a large-scale structure

1. Optical Galaxy Survey On SERC J-Sky Survey Films Eye survey with a binocular-type microscope We detected 4158 galaxies for 6 Schmidt fields upto b=+5° We Measured.Angular size > 4 arcsec.Magnitude Class 1 (bright) – 6(faint).Morphological types

Core of the Ophiuchus cluster in R-Band (UH 88-inch telescope)

2. Identification to 2MASS Positional coincidence < 10 arcsec Among 4158 galaxies, 1471 objects are identified to 2mass sources. (2MASS data were provided by Tom Jarrett)

Examples of 2MASS images (T. Jarrett)

Distribution of Bright Galaxies +:2Mass Counterpart, ・ : No Counterpart

Distribution of Faint Galaxies +; 2MASS counterparts, ・ ; No counterparts

Identified Galaxies in Optical & 2MASS Surveys

2Mass Identification Rate over Optical Becoming poorer bellow b<8°

2MASS Identification Rate -- Optical Brightness Quite incomplete at optically faint galaxies

2MASS Identification Rate – Optical Size Quite Incomplete at small-size galaxies

K T Magnitude Distribution – b Detection Limits goes worse bellow b< 10°

Result 1. Optical survey is much deeper than 2mass even low b 2. 2mass detection rate is poor bellow |b| < 10deg 3. 2MASS detection rate decreases for fainter and smaller galaxies 4. However, 2MASS detection is still powerful due to its uniformity

3. Redshift Survey with 6dF 250B grating 3800 < λ < 7500 (3.7 A/pixel) 3 hours for a field Survey area: From Ophiuchus cluster towards Hercules cluster for studies of a large-scale structures We put fibers more than 2500 targets.

From 2MASS Redshift Survey by Huchra

Troubles in the Milky Way High Foreground star density (log d=4.5) -> Contamination of adjacent star light Galactic Diffuse HII Region -> Contamination of Galactic Emission Lines High Obscuration -> Incomplete target galaxy survey

Damaged Spectrum by a foreground star light

Damaged Spectrum by Galactic Emission Lines

cz Success Rate (for 2MASS objects) – b Remain at high rate even at low b

cz Success Rate (for non-2MASS objects) – b Almost as high rate as 2MASS objects

cz Success rate – Log (Foreground star density) High rate even at high star density region

cz success rate – K T Magnitude 60% at K T =13.0 even in the Milky Way

Success/Failure in cz Measurement on (K T – b) Plot No Sharp Boundary

cz - Galactic b Few large cz (20,000 km/s) objects at low b

4. Large-Scale Structure Is the Ophiuchus cluster a suparcluster? Yes (Hasegawa et. al.,MN.,2000) If so, is the supercluster connected to Hercules supercluster with a wall? Probablly Yes (Wakamatsu et al.,2000) Probablly a Key Cluster for large-scale structure as Coma cluster is

Distribution of Galaxies in Optical Survey Hercules cluster

Velocity Histogram showing the Ophiuchus supercluster

Cone diagram showing a structure connecting Ophiuchus - Hercules superclusters

The Great Wall (copy from cfa) Hercules cluster

5. Summary & Suggestion We can penetrate deep into the Galactic plane upto log (star density) =4. & upto fainter level K T =12.8 Check adjacent foreground stas on 2MASS images Galactic diffuse emission lines are not serious for cz measurement It is better to get low dispersion spectra

VIVA! May 31, 02 At Sydney 6dF Redshift Survey deep into the Galactic Plane