LINERs: The X-ray Perspective John McNulty

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

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)

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

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

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

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

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

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

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?

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

No apparent correlation – more data needed

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

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

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)