LowLuminosity AGNs

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Low-Luminosity AGNs

• Jim Ulvestad

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Outline

• Reprise of VLBA Capabilities
• AGNs with 107-108 MSun Black Holes
• Surveys and searches for BBHs in LLAGNs
• A few random thoughts about starburst and other
  galaxies

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VLBA Frequencies Sensitivity

• Current sustainable data rate is 256 Mbit/s
• Aiming for 4 Gbit/s peak by 2010, sustainable
  later
• Significantly higher data rate in 2015 era?

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VLBA Angular Resolution

• Note that 60 µJy in 0.8 mas (4cm) corresponds to
  TB 1.1x106 K
• This implies that one is most likely to detect
  only nonthermal radiation from near black holes,
  or possibly thermal emission from X-ray-emitting
  accretion flows

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VLBA Angular Resolution in BH Units

• VLBA resolution typically is about 1000-10,000
  Schwarzschild radii
• A few exceptions in the range of 100
  Schwarzschild radii

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Fundamental Plane for BH Mass
Radio/X-ray/BH mass relation (Merloni et al. 2003)
Seyferts at 1021 W/Hz, 107-108 MSun
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Resolution for Nearby AGNs

• At a distance of 20 Mpc, resolution of 0.02 to
  0.1 pc is achievable
• Motions of 0.01 pc or smaller could be detectable
• Corresponds to binary BH orbital speeds of 0.03c
  in 1 yr
• Many hours per galaxy?

Mrk 421, 501
M87, N4151
Nearby GRBs?
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Seyfert VLA Radio Spectra

• Flat-spectrum objects might be best candidates to
  harbor binary BHs

Ulvestad Ho 2001
U
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Low-Lum. Seyfert VLBA Cores

• Unresolved, rising spectra (Ulvestad Ho 2001
  Anderson et al. 2004)
• Flat-spectrum objects unresolved by VLBA
• Size upper limits of a few thousand Rg for BH
  masses of 107-108 MSun

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VLBI Core of NGC 4151

• NGC 4151 has BH of 107 MSun
• 15 GHz VLBI image at the right used
  VLBAVLAGBTEb (Ulvestad et al. 2005)
• How many objects will look like this with very
  high sensitivity?
• How many Seyferts can we look at?

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Surveys for Binary BHs in LLAGNs?

• CJF has 1/300 radio binary BHs
• VIPS may have 0/1100 radio binary BHs?
• What is the frequency of BBHs in lower luminosity
  AGNs with lower mass black holes?
• Seyfert and Low luminosity AGN surveys?
• Much higher space density of objects, but the
  radio sources are much weaker
• Need 4 Gbit/s and 1 hour on source per galaxy for
  LLAGNs at 1 mJy and above (2 hr/galaxy of total
  observing time)

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Weak Seyferts (Ho 1995 UHo 2001)

• Add Markarian and other Seyferts to increase
  sample VLBA could image to 100-200
• Density of 200 objects per (100 Mpc)3 with P6cm
  gt 3 x 1021 W/Hz
• This is 1 mJy at 50 Mpc distance
• 400 hr of VLBA time at 8 GHz, 4 Gbps

Log (6 cm Flux Density)
1 mJy
Log O III Flux
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Double AGN Surveys with VLA?

• Significant fraction of Markarian galaxies have
  double optical nuclei
• These have never been surveyed systematically
  with the VLA
• Could a VLA survey tell us anything useful about
  the incidence of smaller-separation BBHs?

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NGC 3256Merger with Double AGN?

• Colorsoptical DSS
• ContoursHI (Hibbard et al.)

• RedULXs (Lira et al. 2002)
• Radio (Neff, Ulvestad, Campion 2003)

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Arp 299 Birth of Small BHs?
HST WFPC2

• Detected
• Supernova factory in merging galaxy pair
• Very young supernova in E nucleus
• Recently detected new radio SN (not shown) in
  early 2005 in W nucleus
• Birth of stellar-mass BHs in starburst/merger
  galaxies such as Arp 220, Antennae

3 PC
1 HST/PC2 pixel
Neff et al. 2004 Ulvestad in prep.
2.3 GHz, 4/02
8.4 GHz, 2/03
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Backup Slides
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NGC 3256 The Nuclei

• 8.4 GHz and 15 GHz VLA images of two nuclei (with
  X-ray positions indicated)

• 1.5-10 keV contours (Chandra archive)

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European VLBI Network

• http//www.evlbi.org
• Operated by national agencies in Europe
• Antennas of different sizes and capabilities
• Strengths
• Some large apertures, and higher bandwidth
• Sensitive short/intermediate spacings
• eVLBI capabilities
• Handy sensitivity calculator for mixed arrays!
• Weaknesses
• Fixed observing schedules
• Sessions limited to lt 10 weeks/yr
• Non-uniform antenna capabilities
• High-frequency capabilities limited
• Yebes, Sardinia telescopes will help