X-Ray Surveys Greg Hallenbeck 7 April 2010 Brandt & Hasinger - - PowerPoint PPT Presentation

X-Ray Surveys

Greg Hallenbeck 7 April 2010 Brandt & Hasinger 2005 Vikhlinin et. al 2009 Vikhlinin et. al 2009

Overview

• Previous Surveys using Chandra and

XMM-Newton

• How are they different?
• What have they found?
• What science does this enable?
• Future Surveys with WFXT and IXO
• How are they different?
• What science will be made possible?

Past and Current Surveys

Blue: Chandra Green: XMM-Newton Purple: Earlier Both telescopes have significantly pushed down flux limits, but their surveys cover very small areas as a consequence of long exposure times

Satellite Data

• Chandra
• Position Accuracy < 1”
• Background ~1 count / 2 months / pixel (0.5-8 keV)
• Almost no source confusion
• X-Ray Multi-Mirror Misson-Newton (XMM-Newton)
• Position Accuracy 1-3”
• Wider Field of View (2.5x Chandra's)
• Larger Collection Area
• Tends to cover larger solid angle

Source Counts and Classification

• Each survey has about 100-600 detections over

areas of 0.1-10 square degrees

• Many sources very faint optically
• Get poor or nonexistent optical spectra
• So, low completeness in:
• Redshift data (50-70%)
• Classification (< 60%)

Source Types

• AGNs
• Unobscured (0 < z < 5)
• Obscured in X-Ray but not optical/UV (z < 1.5)
• Optically Faint X-Ray Sources (1 < z < 4) (Obscured

AGNs?)

• X-Ray Bright, Optically Normal Galaxies (XBONGs) (0.05 <

z < 1)

• Other Stuff
• Starburst Galaxies (0.1 < z < 1.5)
• Galaxies and Groups (0.1 < z < 1)
• X-Ray Bright Galactic Stars

Sources Found (0.5-2 keV)

Sources Found (2-8 keV)

Cosmic X-Ray Background (CXRB)

• Discovered by Giacconi et. Al 1962
• Appeared nearly uniform over entire sky
• Later found to be mostly AGNs (~70%), but has only

been partially resolved

• Resolution Levels by these surveys:
• Have resolved ~90% of 0.5-2keV CXRB

– Previously 75% by ROSAT

• ~85% at 2-6keV
• ~60% at 6-10keV

AGN Evolution / SMBH Growth

Schmidt 1968 shows growth in number density of AGNs with z (for low z) But at deeper redshifts... Number density of moderate luminosity AGNs peak near z = 2 before dropping off sharply Can use this luminosity function to estimate SMBH masses

Demographics and Physics of High z AGNs

• The surveys are sensitive enough to detect

moderate strength AGNs at high z > 4

• Huge volume gives statistics on “typical” AGNs
• Optical surveys just see the biggest
• Some Findings:
• Distant AGNs seem to accrete in the same modes

as local AGNs

• AGNs did not dominate reionization

Surveys with WFXT: The Wide-Field X-Ray Telescope

Goal of Chandra and XMM-Newton sensitivity, but over a large area of the sky (10-25%) With estimated 100

• bjects per sq. deg,

should get tens of thousands of objects FOV of 1 sq. deg 8,000cm² collecting area

Cluster Mass Function Science

Cluster mass function is sensitive to ΩΛ and ΩM WFXT would be able to measure cluster masses out to z=2 (when they showed up) But the cluster mass function can also be used to measure the...

Growth Factor of Density Perturbations G(z)

• Indicates how small primordial

fluctuations increase with time

• G(z) increases as z decreases
• Note that the y axis is multiplied

by (1+z)

• WFXT provides independent

measure for z < 1 (shown in blue)

• Non-GR theories tend to predict

fairly different values

• DGP Model (dashed)
• Quintessence (solid)

Other Science with WFXT

• Find statistics of many unusual objects like the “Bullet

Cluster” with greatly increased search volume

• Used to find departures

from ΛCDM

• More detailed measurement
• f mass-dependent power

spectrum of groups and clusters

• Measure cluster-cluster correlation function on non-linear

scales, and over wide range of spatial scales

Surveys with IXO: The International X-Ray Observatory

• WFXT should find a lot of objects, but not collect

much information on each object

• IXO has both greater:
• Collecting Area
• Spectroscopic Resolution
• Even for high z > 2 objects, still high precision on
• Temperature
• Metallicity
• Velocity Structure

Science Made Possible with IXO

• Measure gas fraction in large, dynamically

relaxed clusters

• Use fgas ~ d

3 / 2 trend to get d(z)

and constrain ΩΛ, and Ωm

• Extend G(z) to z > 2
• Possibly as good as JDEM
• Measure “growth index” γ
• Non-GR theories give fairly

unique values

Fin

(The pun seemed funny at 3am while I was observing)