the clustering of galaxies detected by neutral hydrogen emission
DESCRIPTION
Sean Passmoor Prof. Catherine Cress Collaborators Andreas Faltenbacher, Ando Ratsimbazafy Ben Hoyle, Russell Johnston, Mathew Smith. The clustering of galaxies detected by neutral hydrogen emission. Galaxy Clustering in Radio surveys: HI & continuum sources. Introduction. - PowerPoint PPT PresentationTRANSCRIPT
Sean PassmoorProf. Catherine Cress
CollaboratorsAndreas Faltenbacher, Ando Ratsimbazafy Ben Hoyle, Russell Johnston, Mathew Smith
Galaxy Clustering in Radio surveys:HI & continuum sources
Introduction
Why Measure Clustering:• Compare galaxy populations & relationship with dark
matter
• Evolution of clustering dependent on (ΩΛ; Ω
m)
• Constrains nature of Dark Matter (e.g. Hot Dark Matter Evolves Differently)
What is bias:• Relates fluctuations of DM to that of galaxies• Important for galaxy evolutionary theory• Predictions for SKA experiments
Angular Correlation Function
Probability of Finding 2 sources separated by a given angle
For Random Samples ω(θ)=0
ω θ = DD θ RR θ
−1
Illustration: Angular Correlation Function for an Artificial Distribution
•The fake data clustered on ±10° scale
• The Random Data is evenly distributed over the field
Current Neutral Hydrogen Surveys
HIPASS Survey (Blue)• Area = 20 000 deg2
• Depth z ≈ 0.02• 4315 HI sources
ALFALFA Survey (Red)• Area ≈ 400 deg2
• Depth z ≈ 0.06• 1796 HI sources
Redshift Distribution
Angular Correlation Function for HIPASS & ALFALFA
.Compare correlation function of HI-galaxies with dark matter to measure bias
Recap
We find agreement between the clustering strengths of the two surveys.
Note : since bias < 1 → anti-biased
Measured BIAS parameter
ALFALFA 0.52 ± 0.1
HIPASS 0.68 ± 0.1
Galaxy Clustering in Radio surveys:continuum sources
Continuum sources Synchrotron emission High redshift
• Faint Images of the Radio Sky at Twenty-Centimeters
~10000 deg2
~ 90 sources per deg2 at 1mJy
• Matched to SDSS (overlap ~4600 deg2)
Photometric Redshift Distribution
Matched Probe z < 1
• S3 Simulation – Theoretical Prediction of Redshift Distro.
Galaxy Clustering in Radio surveys:continuum sources
Continuum sources Synchrotron emission High redshift
• Faint Images of the Radio Sky at Twenty-Centimeters
~10000 deg2
~ 90 sources per deg2 at 1mJy
• Matched to SDSS (overlap ~4600 deg2)
Photometric Redshift Distribution
Matched Probe z < 1
• S3 Simulation – Theoretical Prediction of Redshift Distro.
Galaxy Clustering in Radio surveys:continuum sources
Continuum sources Synchrotron emission High redshift
• Faint Images of the Radio Sky at Twenty-Centimeters
~10000 deg2
~ 90 sources per deg2 at 1mJy
• Matched to SDSS (overlap ~4600 deg2)
Photometric Redshift Distribution
Matched Probe z < 1
• S3 Simulation – Theoretical Prediction of Redshift Distro.
• Unmatched Sources– Probes deeper
• By Measuring the clustering of unmatched FIRST we probe bias at high-z
Faint Images of the Radio Sky at Twenty-Centimeters
Ongoing ...
• Matched Sources– Matched Probe z < 1
• Unmatched Sources– Probes deeper
• Way Forward
– ???
Matched sample
contains a mixed
population?
Summary
HI Clustering Studies
• Both ALFALFA & HIPASS indicate an anti-bias– i.e. less clustered than dark matter
Continuum Clustering Studies
• The Bias Calculation is ongoing