The Bulgeless Seyfert/LINER Galaxy NGC 3367: Disk, Bar, Lopsidedness and Environment1 H. M. Hern´andez-Toledo2,a, M. Cano-D´ıaza,b, O. Valenzuelaa, I. Pueraric, J. A. Garc´ıa-Barretoa, E. Moreno-D´ıaza, H. Bravo-Alfarod aInstituto de Astronom´ıa, Universidad Nacional Aut´onoma de M´exico, Apartado Postal 70-264, Mexico D.F., 04510, Mexico bINAF-Osservatorio Astronomico di Roma, via di Frascati 33, 00040, Monte Porzio Catone, Italy cInstituto Nacional de Astrof´ısica, Optica´ y Electr´onica, Calle Luis Enrique Erro 1, 72840, Sta. Mar´ıa Tonantzintla, Puebla, Mexico dDepartamento de Astronom´ıa, Universidad de Guanajuato, Apdo. Postal 144, Guanajuato 36000, Mexico ABSTRACT NGC 3367 is a nearby isolated active galaxy that shows a radio jet, a strong bar and evidence of lopsidedness. We present a quantitative analysis of the stellar and gaseous structure of the galaxy disk and a search for evidence of recent interaction based on new UBV RI Hα and JHK images and on archival Hα Fabry-Perot and HI VLA data. From a coupled 1D/2D GALFIT bulge/bar/disk decomposition an (B/D ∼ 0.07-0.1) exponential pseudobulge is inferred in all the max observed bands. A NIR estimate of the bar strength <QT (R) > = 0.44 places NGC 3367 bar among the strongest ones. The asymmetry properties were studied using (1) optical and NIR CAS indexes (2) the stellar (NIR) and gaseous (Hα, HI) A1 Fourier mode amplitudes and (3) the HI integrated profile and HI mean intensity distribution. While the average stellar component shows asymmetry values close to the average found in the Local Universe for isolated galaxies, the young stellar component and gas values are largely decoupled showing significantly larger A1 mode amplitudes suggesting that the gas has been recently perturbed. NGC 3367 is devoided of HI gas in the central regions where a significant amount of molecular CO gas exists instead. −2 Our search for (1) faint stellar structures in the outer regions (up to µR ∼ 26 mag arcsec ), (2) (Hα) star-forming satellite galaxies and (3) regions with different colors (stellar populations) along the disk all failed. Such an absence is interpreted using recent numerical simulations to constrain a tidal event with an LMC like galaxy to some dynamical times in the past or to a current very low mass, gas rich accretion. We conclude that a cold accretion mode (gas and small/dark galaxies) may be responsible of the nuclear activity and peculiar (young stars and arXiv:1104.3622v4 [astro-ph.CO] 26 Apr 2011 gas) morphology regardless of the highly isolated environment. Black hole growth in bulgeless galaxies may be triggered by cosmic smooth mass accretion. Subject headings: Galaxies: individual – Galaxies: structure – Galaxies: bars – Galaxies: photometry – Galaxies: interactions – Galaxies: morphology – Galaxies: general 1. Introduction 1Based on data obtained at the 0.84m, 1.5m and 2.1m telescopes of the Observatorio Astron´omico Nacional, San NGC 3367 is a nearby barred galaxy that is Pedro M´artir operated by the Instituto de Astronom´ıa, classified as SB(rs)c in the Third Reference Cata- Universidad Nacional Aut´onoma de M´exico. log of Bright Galaxies (de Vaucouleurs et al. 1991, hereafter RC3) and as Sy 2-like, HII in V´eron- Cetty & V´eron (1986). MIR Spitzer observations 1 of NGC 3367 reveal the presence of [Ne v] lines at measurements as constraints to the recent dynam- 14.3µm and 24.3µm with X-ray luminosity domi- ical history in NGC 3367. Specifically, a descrip- nated by a power law with 2-10 keV luminosities tion of observations and the techniques used in the of 2.0 ×1040erg s−1 (McAlpine et al. 2011). NGC data reduction are briefly described in Section 2. 3367 is located in the field of the Leo Group but In Section 3 we present a brief summary of the it belongs to the background based on its opti- main morphological features found in the optical −1 cal velocity of vo = 2998 km s and the mean and NIR images. A surface photometry analysis velocity ofthe Leo I Group = 900 km s−1 (Fergu- is carried out in Section 4, including (i) an analy- son and Sandage 1990; Stocke et al. 1991; Tonry sis of the surface brightness and color profiles, (ii) et al. 2001). The closest candidate for a galaxy a coupled 1D-2D bulge/disk and bulge/bar/disk companion is NGC 3391 at a projected distance of decomposition into S´ersic, Exponential and Fer- ∼ 563 kpc or 18 optical diameters away (Garc´ıa- rer components. Section 5 presents different bar Barreto et al. 2003) and a recent search for iso- properties like ISM shocks based on the dust lane lated galaxies in the local Universe based on the geometry revealed by a B − I color map, a quan- SDSS has also confirmed that NGC 3367 is an iso- tification of the bar strength and length, and a lated galaxy (Hern´andez-Toledo et al. 2010). The brief discussion of the bar nature in terms of the optical appearance of NGC 3367 is dominated by a Athanassoula & Misiriotis (2002) models. In Sec- bright bar and an apparent large-scale asymmetry tion 6 Lopsidedness is reviewed from various es- or lopsidedness to the southwest side. timators, namely, the Concentration-Asymmetry- Radio observations in NGC 3367 reveal a bipo- Clumpiness (hereafter CAS) parameters in the op- lar synchrotron outflow from the nucleus and two tical and NIR bands, the m = 0 − 2 Fourier NIR large lobes with a total projected extent on the and Hα amplitudes and the VLA HI asymmetry sky (from NE-to-SW) of 12 kpc, resembling a ra- from the moment 0 distribution and the corre- dio galaxy. The axis of the ejected outflow is sponding HI line profile. In Section 7 we look highly inclined with respect to the axis of rotation for (i) evidence of low surface brightness features of the disk (Garc´ıa-Barreto et al. 1998; Garc´ıa- likely related to a tidal origin and (ii) the presence Barreto, Franco & Rudnick 2002). Single-dish HI of recent galaxy accretion events or satellite com- 9 content of MHI ∼ 7 × 10 M⊙ has been reported panions in the observed colors. Section 8 presents for this galaxy (Huchtmeier & Richter 1989) and a general discussion on the origin of the disk Lop- a high fraction of molecular gas has been found sidedness. We use Fabry-Perot Hα and HI VLA mostly concentrated in the central 27′′ (r=5.7 kpc) data to discuss possible evidence of anisotropic gas M(H2) = 2.7 × 109M⊙ (Garc´ıa-Barreto et al. accretion and its possible connection to the AGN 2005). NGC 3367 also shows weak thermal radio activity in NGC 3367. Finally, our summary and continuum emission (at 4.5” angular resolution) concluding remarks are presented in Section 9. A −1 −1 extended throughout the disk (Garc´ıa-Barreto et distance of 43.6 Mpc (Ho = 75 km s Mpc ) is al. 1998) and Hα Fabry-Perot observations in- adopted for NGC 3367 (Tully 1988), resulting in −1 dicate that its rotation axis lies projected on the a linear scale of 210 pc arcsec . disk at a P.A. of 141◦, the N side of that projected line being closer to the observer (Garc´ıa-Barreto 2. Observations and Data Reduction & Rosado 2001). The optical UBV RI observations were carried Despite that several properties of NGC 3367 out at the 0.84m telescope of the Observatorio As- somehow resemble a gravitational interacting sys- tron´omico Nacional at San Pedro M´artir (OAN- tem with another galaxy, there is yet no support- SPM), Baja California, M´exico, with a Site1 CCD ing evidence. This is the first paper of a series detector yielding a total field of view of 7.2 x 7.2 where we present our multi-wavelength data and arcmin and typical seeing FWHM values of 1.8 discuss some alternatives to the origin of the ob- arcsec. A detailed description of the optical ob- served morphology and asymmetries. Our paper is servations and the standard data reduction within split into two general parts; one describing the ob- servations and the estimate of the galaxy parame- ters and the second discussing the interpretation of 2 the IRAF platform 3 can be found in Garc´ıa- then subtracted from the original image to en- Barreto et al. (2007). The routines under Space hance both internal and external structures in the Telescope Science Data Analysis System (STS- form of star forming regions, structures embedded DAS) were used in the reduction and analysis of into dusty regions or faint outer details of partic- both the optical and near-IR data. In this pa- ular interest for our discussion. per a further processing of the images in 2 × 2 The bluer bands highlight a sharp semi-circular binning mode was applied to have a pixel scale outline at the N-W-S direction. This structure of 0.85 arcsec/pix, similar to that in the Near-IR presents a complex pattern of arms at a radius observations. of about 50 arcsec (10 kpc) from the center. The The Near-IR observations were carried out us- arms in the inner region almost coalesce to form an ing the CAMILA instrument (Cruz-Gonz´alez et internal ring. Some bright HII regions are strung al. 1994) at the OAN-SPM 2.1m telescope. The along the inner parts of two major arms that begin CAMILA instrument uses a NICMOS 3 detector at the ends of the bar, these arms experiencing of 256 x 256 pixel format.