VLBI observations of the water megamaser in the nucleus of the Compton-thick AGN IRAS VLBI observations of the water megamaser in the nucleus of the Compton-thick AGN IRAS Paola Castangia (INAF-OA Cagliari) Collaborators: Alessandro Caccianiga (INAF-OA Brera) Paola Severgnini (INAF-OA Brera) Andrea Tarchi (INAF-OA Cagliari) Roberto Della Ceca (INAF-OA Brera)

Disk-masers PV diagram  θ S,V R Velocity drift  R S D = R S / θ S D U3789 = 49.6±5.1 Mpc M BH = (1.16±0.12) × 10 7 M SUN (Reid et al. 2013) (Reid et al. 2009) D N4258 = 7.2±0.5 Mpc M BH = (3.9±0.3) × 10 7 M SUN (Herrnstein 1999)

Jet-masers Jet-cloud interaction Mrk 348 (Peck et al. 2003) Continuum and line flux densities are correlated Reverberation maps give: V shock, ρ j, ρ 0

Outflow-masers: Circinus H 2 O masers trace a warped edge-on accretion disk and a wide-angle outflow –Outflow l.o.s velocity: ± 160 km/s –The warps collimate the outflow (Greenhill et al. 2003)

IRAS kpc WISE Multi-Colour image Compton-thick (N H > cm -2 ) AGN sample Selection method: FIR and X-ray flux and colours (Severgnini et al. 2012) Ongoing H 2 O maser survey An S0 galaxy at ~130 Mpc The nucleus: Sy2 with broad Hα in pol. (weak) (Young et al. 1996) Unresolved radio source (VLA A, 8.4 GHz) (Schmitt et al. 2001) Radio quiet (L 5GHz /L 2-10keV = -5) (Terashima & Wilson 2003)

GBT observations, April 7, 2012 Single-dish observations CO V sys Line 1 Broad (FWHM ~ 90 km/s) Blueshifted (V=8960 km/s) L H2O ~ 200 L sun Channel spacing 0.3 km/s Line 2 Narrow (FWHM < 1 km/s) Systemic (V=9106 km/s) L H2O ~ 15 L sun

Single-dish observations May 12, 2012 April 7, 2012 Channel spacing 3.3 km/s The broad line is variable: Peak and int. flux density decreased to ½ of their initial values in ~1 month The properties of the narrow component remained relatively constant

VLBI observations Details of the observations Telescope: VLBA Dates: June 2 and 3, 2012 (2 x 5 hr) Bands: 2 x 16 MHz IFs Correlation: 128 ch per IF and pol.  ch spacing 1.7 km/s “spectral zooming mode”  ch spacing 0.2 km/s 22 GHz maps Line low res. (rms = 2 mJy/beam) Line high res (rms = 5 mJy/beam) Continuum (from the line-free channels, rms = 0.1 mJy/beam)

VLBI observations VLA, A-array, 8.4 GHz (Schmitt et al. 2001) A B ? 6 pc VLBA, 22 GHz Peak = 0.7 ± 0.1 mJy T B > 3.6 x 10 6 K P 22 ~ 1.4 x W Hz - 1 Tentative Peak ~ 0.5 mJy Slightly resolved 300 pc 0.5”

VLBI observations Source A Source B Source C?

VLBI observations A 3 pc B ? Tentative! Peak ~ 10 mJy Ch. 1.8 km/s Tentative! Peak ~ 12 mJy Ch. 1.8 km/s Ch. 0.2 km/s Peak ~ 42 mJy Line parameters = single-dish spectrum

Investigating the obscured nucleus of IRAS Radio continuum emission T B of sources A and B suggest a non-thermal origin P 22 > W Hz -1  unlikely to be SNRs P 22 larger than average P 5 in a sample of Sy (Panessa & Giroletti 2013) If the tentative source is real  pc linear structure Origin of the maser? Absence of the triple-peak profile  jet/outflow maser Systemic and blueshifted emission separeted by pc  disk-maser unlikely (R ≤ 1 pc) Not associated with any compact continuum source at 22 GHz

Conclusions and future plans Radio continuum emission : VLBA 22 GHz image show 2 (possibly 3) compact continuum sources in a linear structure of tenths of parsecs  ejection processes in the nucleus of IRAS ? The water megamaser in IRAS Systemic and (tentative) blueshifted emission are separated by pc  jet/outflow origin still the most likely Multifrequency (L and C bands) EVN observations have been approved and await scheduling. These will be fundamental to establish the nature of the radio continuum emission from the nucleus Single dish monitoring of the water maser lines with Effelsberg will help shedding light on the origin of the maser