1. LINERs: The X-ray Perspective John McNulty

2. Why X-rays?
Hard (2-10 keV) X-ray point source characteristic of a black hole or AGN
X-rays relatively unaffected by absorption, especially at harder energies
X-rays represent a sizeable fraction of an Active Galaxy’s total luminosity

3. Chandra: Uniquely Suited
Combines high angular resolution (0.5”/pixel) with sensitivity
Covers a broad band: 0.2 – 10 keV
Capable of both imaging and spectroscopy using ACIS (Advanced CCD Imaging Spectrometer)

4. Defining the Sample Distances
27 LINERs observed with Chandra’s ACIS-S
Distances ranged from 690 kpc to 328 Mpc (1 pc = 3.24 light years or 3.09×1016 m)
Most galaxies within 50 Mpc

6. Defining the Sample X-Ray Morphology
Class I: point source (LLAGN?)
Class II: scattered sources
Class III: point in diffuse emission
Class IV: no source

7. Data Analysis
Counts were extracted from a 2” radius circle centered on the nucleus
Using these, a Hardness Ratio (# Hard Counts : # Soft Counts) could be determined
Fluxes and luminosities were calculated assuming an absorbed power law model
(2-10keV, Γ=1.8, galactic NH)
More detailed analysis, using Xspec, was possible for eight of the sample galaxies

8. An Example of Spectral Fitting Markarian 273 in Soft X-rays

9. An Example of Spectral Fitting Markarian 273 in Hard X-rays

10. An Example of Spectral Fitting
Soft X-rays
Hard X-Rays
A model for soft,
diffuse emission
And a model for
a hard point source
Thermal plasma
+ power law
Highly absorbed
power law +
emission line

11. An Example of Spectral Fitting
This spectral fitting raises new questions:
The model suggests a hard energy power law that is very highly absorbed – where does the absorbed flux go?
IR observations can help
Are there IR signs of absorbed and reradiated energy? High excitation lines?

13. More Data
Required
Most Class I galaxies: X-ray luminous and IR faint ?
Class II galaxies
tend to be X-ray
faint and IR bright

14. No apparent correlation – more data needed

15. [CII]/FIR as a function of LFIR
No apparent correlation
No meaningful class
distinctions
More data needed

16. Putting the Pieces Together
Broad Hα observed in 4 of the sample LINERs – all Class I
But . . .
Of the 6 class I LINERs observed by SWS, only 2 show high excitation lines
NGC 5194 (III), NGC 253 (II), NGC 3079 (II), and Mrk273 (III) show high excitation lines
Further observations needed

17. Conclusions
Consistency between multiwavelength AGN diagnostics is critical – Do our IR diagnostics for an AGN point us to the same set of galaxies as our X-ray diagnostics? At this point, the answer is “no.”
Future multiwavelength observations of LINERs will be essential for refining our set of diagnostics, and for ensuring an accurate understanding of LINERs
Future work
Chandra proposal for 80ks observation time, surveying 16 IR bright LINERs has been accepted (IR bright ≈ 80% of LINERs)
Propose for SIRTF (successor to ISO, launches Jan 2003)