# Presentation: 366546

## Active Galactic NucleiWhat are Active Galactic Nucleiand Why Does Anyone Care? Julian Krolik

- Aneta Siemiginowska
- Harvard-Smithsonian Center for Astrophysics
- Chandra X-ray Center

## Outline

- AGN models.
- What have we learned from Chandra and XMM?
- X-ray Jets
- Absorbers and Outflows
- Emission Lines
- Deep Imaging and X-ray background
- Obscured AGN
- AGN activity
- Questions.

## AGN Properties

**Highly luminous:** Lbol  ~10**42** – 10**48** ergs s**-1**
**Compact**: size << 1pc
**Broad-band** continuum emission:  								*dL / dlog****const*.  													From IR to X-rays and -rays
**Variable:** stronger variations on smaller timescales at shorter wavelengths
**Weakly polarized: **1% linear polarization
**Radio emission:** in some sources extended

## AGN Models

*Urry & Padovani 1998*

**AGN Models**

**Supermassive** **Black Hole:**
**          ****M ~ 10****6 –**** 10****9 ****M****o**

**Eddington Luminosity:**                                   **F****rad**** = F****grav    **
**  ****  ****L****E****dd****~1.3 x 10****38****(M/M****o****) **ergs/s

**Accretion Powered:**
- L ~ Mc**2**

- .

- Accretion rate

- Efficiency

## Slide 5

## 3D Vision

- Side – NAL

- Side – BAL

- Top View

*Elvis 2000*

## Slide 7

## What X-rays can tell us?

- Thermal emission from hot gas: 10**5**-10**7** K               							**=> hot gas is there!**
- Non-thermal emission: synchrotron, Comptonization         					**=> relativistic plasma!**

## What X-rays can tell us?

- X-ray emission regions:
**Nucleus** – unresolved component
**Extended emission** on different scales: parsec to hundreds kpc
**Jets and radio lobes**
- Absorption properties:
- Amount of **absorbing** material
- Outflow/Inflow **velocity**
**Cold/Warm** absorbers
**Ionization** State
**Abundance**
- Variability:
**Scale/Size **of the emitting and reprocessing regions

## Chandra can resolve structures on 1arcsec scale

- Chandra **can resolve structures** on 1arcsec scale

**NGC253 – starburst**

## Discoveries happen even in 21st Century

- => crucial for **high dynamic range** observations when  looking at faint  structures in the vicinity of  strong sources
- => discovery of **X-ray jets **

**Discoveries happen ****even**** in 21****st**** Century**

## X-ray Jets

- Many Chandra observations revealed X-ray jets associated with quasars: 													=>**  jets are common** phenomena.
- Some jets were discovered in quasars where there was **no previously known radio jet** emission.                       Examples:  **PKS 1127-145,  B20738+393**
- Relativistic motion at **hundreds kpc** distance from the quasar!

## PKS 1127-145 z=1.187

**PKS 1127-145 z=1.187**

**HST/WFPC2**

**Chandra**

**~300 kpc**

*Siemiginowska et al 2002*

## B2 0738+313 z=0.63

**B2 0738+313 z=0.63**

**X-ray/Radio**

**Radio**

*Siemiginowska et al 2003*

## Jet Models

- Comparison of X-ray, optical and radio data **rules out** thermal emission, SSC and simple direct synchrotron emission as primary source of the X-ray emission.
**Inverse Compton scattering of Cosmic Microwave Background (IC/CMB)** photons on relativistic jet electrons can describe the observations:  							=> Required bulk motion Lorentz factors are higher for lower redshift quasar:    bulk ~10  vs.  bulk~ 2-3
- Are higher redshift quasars more likely to have X-ray jets? (Dan Schwartz Chandra project)

## Absorbers and Outflows

**Optical/UV ****Absorption due to IGM **
**	****=> Studies of Matter in the Universe**

**Ly********  Forest**

**Damped Ly******

*Pettini 2003*

## X-ray Absorption: IGM

*Nicastro et al 2002*

**PKS 2155-304**

**HRC/LETG**

**Absorption Lines **
**=>  due to WHIM                 T~10****6 ****K**

## X-ray Absorption due to Ionized Gas close to the nucleus

**X-ray Absorption due to Ionized Gas** **close to the nucleus**

## MCG 6-30-15

**MCG 6-30-15**

**Chandra/HETG**

**OVII edge**

## MCG 6-30-15  

**MCG 6-30-15  **
**Mkn 766**
**OVII and OVIII broad emission lines**

**XMM-Newton/RGS**

**Emission or Absorption?**

## High velocity outflow in  PG 1211+143 

**High velocity outflow in  PG 1211+143 **

**Fe XXVI Ly******

- S XVI **Ly******

- Mg XII **Ly******

- Velocity of outflowing ionized gas based on the line broadening
-       ~ **0.09-0.1c**

*Pounds et al 2003*

## Emission Lines

- Originate in the nucleus:
- Accreting matter
- Relativistic broadening – Fe -line
- BLR clouds
- Originate in the hot gas away from the nucleus – NLR in Syfert 2

## Slide 23

## Zycki (2003)

*Zycki (2003)*

## A case for a broad line in MCG 6-30-15?

**ASCA**

**Chandra**

*Fabian 2002*

*Lee et al 2002*

**A case for a broad line in MCG 6-30-15?**

## XMM- Newton Observations of Fe-line in Type 1 AGN

*Reeves 2002 (astro-ph/0211381)*

**XMM-Newton EPIC-PN**

**MCG 6-30-15**

**XMM- Newton Observations of Fe-line in Type 1 AGN**

## Deep X-ray Imaging

- Deep Chandra and XMM observations:

*Gilli 2003 (astro-ph/0303115)*

## Source Counts:  Log N – log S

**Source Counts:  Log N – log S**

*Gilli 2003(astro-ph/0303115)*

## Extragalactic X-ray Background 0.2-400 keV

*Gilli 2003(astro-ph/0303115)*

**Extragalactic X-ray Background 0.2-400 keV**

*Fabian 2003 (astro-ph/0304122)*

**DATA**

**Making XRB**

**Compton **
**Thick **

**Thin**

**Type 1**

**Total**

## Absorbing Column Density in CDFS

**Absorbing Column**

**Luminosity (2-10) keV**

**Redshift**

**Absorbing Column Density in CDFS**

*Gilli 2003*

## Obscured AGN

* **Fabian (2003, astro-ph/0304122)*

**NGC 6240 BeppoSAX**

**IRAS 09104+4109**

**3C294**

**A18**

- * **Large number** of obscured sources!
- * What is **the evolution of obscured **sources?
- * Why they have **large absorbing** columns?
- * What is their black hole  **mass distribtion**? Are they less massive?

## AGN Activity

- Is the AGN always on? Or its activity is  intermittent?
- AGN in clusters

- => evidence for the past activity in forms of *buoyant bubbles?*

*Fabian 2001*

- Perseus A

-   Low Luminosity AGN      M87, SgrA*, IC1459

## Galactic Center  

**Galactic Center  **
**	****	****	****	****	****=> was our Galaxy active in the past?**

* **Baganoff 2003*

**Low Mass BH **
**	****~10****6**** M****o**

## Summary

- AGN models
- X-ray Jets
- Absorption vs. Emission
- Source counts and obscured AGN
- AGN activity

## Slide 35