Star formation and gas inflows in the OH Megamaser galaxy IRAS03056+2034

We have obtained observations of the OH Megamaser galaxy IRAS03056+0234 using Gemini Multi-Object Spectrograph (GMOS) Integral Field Unit (IFU), Very Large Array (VLA) and Hubble Space Telescope (HST). The HST data reveals spiral arms containing knots of emission associated to star forming regions. The GMOS-IFU data cover the spectral range of 4500 to 7500 \AA\ at a velocity resolution of 90 km s$^{-1}$ and spatial resolution of 506 pc. The emission-line flux distributions reveal a ring of star forming regions with radius of 786 pc centred at the nucleus of the galaxy, with an ionized gas mass of 1.2$\times$ 10$^{8}$M$_{\odot}$, an ionizing photon luminosity of log Q[H$^{+}$]=53.8 and a star formation rate of 4.9 M$_{\odot}$ yr$^{-1}$. The emission-line ratios and radio emission suggest that the gas at the nuclear region is excited by both starburst activity and an active galactic nucleus. The gas velocity fields are partially reproduced by rotation in the galactic plane, but show, in addition, excess redshifts to the east of the nucleus, consistent with gas inflows towards the nucleus, with velocity of $\sim$45 km s$^{-1}$ and a mass inflow rate of $\sim$7.7$\times$10$^{-3}$ M$_{\odot}$ yr$^{-1}$.Comment: To be published in MNRA

The OH Megamaser galaxy IRAS11506-3851: an AGN and starformation revealed by multiwavelength observations

We present Gemini Multi-Object Spectrograph (GMOS) Integral Field Unit (IFU), Hubble Space Telescope (HST) and Very Large Array (VLA) observations of the OH Megamaser (OHM) galaxy IRAS 11506-3851. The HST images reveal an isolated spiral galaxy and the combination with the GMOS-IFU flux distributions and VLA data allow us to identify a partial ring of star-forming regions surrounding the nucleus with a radius of ~ 500 pc. While this ring shows starburst excitation and low velocity dispersion, the region internal to the ring shows higher excitation and velocity dispersion values, with values increasing towards its borders at ~ 240 pc from the nucleus, resembling a projected bubble. The enhanced excitation and velocity dispersion of this bubble surrounds a 8.5 GHz radio emission structure, supporting its origin in a faint AGN that is mostly shocking the surrounding gas via a plasma ejection seen in radio at the present stage. This is the fourth of the 5 OHM galaxies we have studied so far (from our sample of 15 OHM) for which GMOS-IFU data indicate the presence of a previously unknown faint AGN at the nucleus, consistent with the hypothesis that OHM galaxies harbor recently triggered AGN

Gemini IFU, VLA, and HST observation of the OH Megamaser Galaxy IRAS17526+3253

We present a multiwavelength study of the OH megamaser galaxy (OHMG) IRAS17526+3253, based on new Gemini Multi-Object Spectrograph Integral Field Unit (GMOS/IFU) observations, Hubble Space Telescope F814W and H$\alpha$+[N{\sc ii}] images, and archival 2MASS and 1.49GHz VLA data. The HST images clearly reveal a mid-to-advanced stage major merger whose northwestern and southeastern nuclei have a projected separation of $\sim$8.5kpc. Our HST/H$\alpha$+[N{\sc ii}] image shows regions of ongoing star-formation across the envelope on $\sim$10kpc scales, which are aligned with radio features, supporting the interpretation that the radio emission originates from star-forming regions. The measured H$\alpha$ luminosities imply that the unobscured star-formation rate is $\sim$10-30\,M$_{\odot}$yr$^{-1}$. The GMOS/IFU data reveal two structures in northwestern separated by 850\,pc and by a discontinuity in the velocity field of $\sim$~200~km~s$^{-1}$. We associate the blue-shifted and red-shifted components with, respectively, the distorted disk of northwestern and tidal debris, possibly a tail originating in southeastern. Star-formation is the main ionization source in both components, which have SFRs of $\sim$2.6-7.9\,M$_{\odot}$yr$^{-1}$ and $\sim$1.5-4.5\,M$_{\odot}$yr$^{-1}$, respectively. Fainter line emission bordering these main components is consistent with shock ionization at a velocity $\sim$200~km~s$^{-1}$ and may be the result of an interaction between the tidal tail and the northwestern galaxy's disk. IRAS17526+3253 is one of only a few systems known to host both luminous OH and H$_{2}$O masers. The velocities of the OH and H$_{2}$O maser lines suggest that they are associated with the northwestern and southeastern galaxies, respectively.Comment: 19 pages, 13 figures, 3 tables, Accepted for publication in MNRA