Observational signatures of gas flows toward the center of galaxies Thaisa Storchi Bergmann Instituto de Física, UFRGS, Brazil Collaborators: Barbosa, Riffel, Dors Jr., Simões Lopes, Winge, Axon, Robinson, Fathi, Ostlin, Marconi Gas accretion and Star Formation in Galaxies, Garching Research Center, Sept Credit:Jon Lomberg

Motivation AGN paradigm: Nuclear activity as phase in galaxy evolution triggered by mass accretion to the nuclear supermassive blackhole (SMBH) (Ferrarese & Merrit 2000; Tremaine 2002; Marconi & Hunt 2003, Peterson & collabs ) Main unsolved questions in AGN research: Origin of fuel; Nature of triggering mechanism How gas is transferred from galactic scales to the nucleus → inflows! But observations show outflows, not inflows!

Nuclear morphology: Simões Lopes, Storchi-Bergmann, Martini 2007: structure maps of HST images of paired sample active vs. non-active galaxy from Palomar survey; 68 pairs Active Non-active Active Non-active Active Non-active

Simões Lopes et al. 2007: Results for 34 early-type pairs: Dust structures/spirals in ALL active galaxies but in only 27% of non-active → feeding material on its way in Previous works: Van Dokkum & Franx 1995, Pogge & Martini, 2002; Martini et al. 2003, Xilouris & Papadakis 2002, Ferrarese et al. 2006, Lauer et al. 2005; Prieto et al → association with activity not so clear “Side result”: non-active galaxies have stellar disks (talk by Bureau, this conference) Active Non-active Active Non-active

Simões Lopes et al. 2007: Results for 34 late-type pairs: Dust structures in both active and non-active galaxies Many non-active galaxies have star-forming nuclei → If dusty structures is the gas in its way towards the nucleus: nuclear spirals also responsible to send gas in to feed starbursts Active Non-active Active Non-active

Inner kpc morphology support nuclear spirals (~100 pc scales) as means to feed AGN and nuclear starbursts. But: where are the kinematic signatures? Storchi-Bergmann, Fathi, Axon, Robinson, Marconi, : proposed GMOS IFU observations to look for streaming motions along nuclear spirals in AGN hosts. Sample extracted from Simões Lopes et al (structure maps). Observational constraints: (1)Low-luminosity AGN, as high-luminosity ones are dominated by outflows; (2)intermediate inclination to measure kinematics; (3)presence of ionized gas to allow optical IFU. Signatures of feeding: gas kinematics

Luminous (M B =-21.2) SBb galaxy at 17 Mpc with nuclear ring (700 pc); LLAGN with double-peaked Balmer lines (Storchi-Bergmann et al ) HST ACS FR656N images of inner 500 pc: gas/dust filaments (Prieto et al. 2005; Fathi et al. 2006) Results: 1) NGC 1097 Fathi et al. 2006:

Results: (1)Non-circular motions: residuals (~50 km/s) delineate spiral arms (dots) seen in structure map; (2)redshifts in the near side, blueshifts in the far side → streaming motions along spiral arms towards the nucleus Fathi et al. 2006: Gemini IFU GMOS Hα spectra covering 7  15  (3 fields; 3000 spectra) → Near side Far side

Results: 2) NGC6951 Galaxy SABbc galaxy at 24 Mpc with LLAGN (LINER/Sy 2), with star- forming ring at ~ 500 pc from nucleus Has radio, CO and HCN emission IFU fields→ Structure map shows nuclear spirals →

Storchi-Bergmann et al Results Streaming motions along nuclear spirals Plus: outflow produced by radio jet (Saikia et al. 2002) Near side Far side

Results: 3) M81 (preliminary) FOV too small to fit a kinematic model But distorted isovelocity curves evidentiate non-circular motions Location of the distortions ↔ dusty structures

Relevance and implications First time that streaming motions in nuclear spirals are mapped – previously only in large scale spiral arms and bars (Visser 1980; Tilanus & Allen 1991; Mundell 1999 for NGC4151; Adler & Westfall for M81; Emsellen, Fathi, Peletier et al ; van Gorkom, Blitz, Walter, this conference) Nuclear spirals ubiquitous in active and late-type galaxies → material in its way in to feed the SMBH and star-forming nuclei; Timescales: at 50 km/s, gas at ~1 kpc from center will reach the nucleus in ~10 7 yrs Calculation of mass inflow rate (of ionized gas!):  ~ nuclear accretion rate to drive the luminosity of the low-lum. AGNs  BUT: ionized gas may be only the “tip of the iceberg”; neutral and molecular gas may dominate inflow (nuclear molecular mass ~ 10 7 M sun in NGC6951; Garcia-Burillo et al. 2000, Krips et al. 2007; nuclear starburst of 10 6 M sun in NGC1097, Storchi-Bergman et al. 2005, Davies et al. 2006; also strong CO recently measured from the nucleus, priv. comm.)

Conclusions Strong correlation between dusty nuclear structures and activity → nuclear spirals can be channels to feed the nucleus; SMBH or starburst First kinematic signatures of inflow towards low-lum. AGNs (in nuclear spirals) More targets to be observed, including Seyferts and starbursts Jon Lomberg: artistic view of mass inflow along nuclear spiral arms