Rubén Joaquín Díaz

Luminous Infrared Galaxies. III. Multiple Merger, Extended Massive Star Formation, Galactic Wind, and Nuclear Inflow in NGC 3256

We report detailed evidence for multiple merger, extended massive star formation, galactic wind, and circular/noncircular motions in the luminous infrared galaxy NGC 3256, based on observations of high-resolution imaging (Hubble Space Telescope, ESO NTT), and extensive spectroscopic data (more than 1000 spectra, collected at Estacion Astrofisica de Bosque Alegre, Complejo Astronomico el Leoncito, Cerro Tololo InterAmerican Observatory, and IUE observatories). We find in a detailed morphological study (resolution ~15 pc) that the extended massive star formation process detected previously in NGC 3256 shows extended triple asymmetrical spiral arms (r ~ 5 kpc), emanating from three different nuclei. The main optical nucleus shows a small spiral disk (r ~ 500 pc), which is a continuation of the external one and reaches the very nucleus. The core shows blue elongated structure (50 pc × 25 pc) and harbors a blue stellar cluster candidate (r ~ 8 pc). We discuss this complex morphology in the framework of an extended massive star formation driven by a multiple merger process (models of Hernquist et al. and Taniguchi et al.). We study the kinematics of this system and present a detailed Hα velocity field for the central region (40 × 40; rmax ~ 30 ~ 5 kpc), with a spatial resolution of 1 and errors of ±15 km s-1. The color and isovelocity maps show mainly (1) a kinematic center of circular motion with spider shape, located between the main optical nucleus and the close (5) mid-IR nucleus and (2) noncircular motions in the external parts. We obtained three sinusoidal rotation curves (from the Hα velocity field) around position angle (P.A.) ~55°, ~90°, and ~130°. In the main optical nucleus we found a clear outflow component associated with galactic winds plus an inflow radial motion. The outflow component was also detected in the central and external regions (r ≤ 5–6 kpc). The main axis of the inflow region (P.A. ~ 80°) is practically perpendicular to the ouflow axis (at P.A. ~ 160°). We analyze in detail the physical conditions in the giant H II regions located in the asymmetric spiral arms, the two main optical nuclei, and the outflow component (using long-slit spectroscopy, plus standard models of photoionization, shocks, and starbursts). We present four detailed emission-line ratios (N II/Hα, S II/Hα, S II/S II), and FWHM (Hα) maps for the central region (30 × 30; rmax ~ 22 ~ 4 kpc), with a spatial resolution of 1. In the central region (r ~ 5–6 kpc) we detected that the nuclear starburst and the extended giant H II regions (in the spiral arms) have very similar properties, i.e., high metallicity and low-ionization spectra, with Teff = 35,000 K, solar abundance, a range of Te ~ 6000–7000 K, and Ne ~ 100–1000 cm-3. The nuclear and extended outflow shows properties typical of galactic wind/shocks, associated with the nuclear starburst. We suggest that the interaction between dynamical effects, the galactic wind (outflow), low-energy cosmic rays, and the molecular+ionized gas (probably in the inflow phase) could be the possible mechanism that generate the similar extended properties in the massive star formation, at a scale of 5–6 kpc! We have also studied the presence of the close merger/interacting systems NGC 3256C (at ~150 kpc, ΔV = -100 km s-1) and the possible association between the NGC 3256 and 3263 groups of galaxies. In conclusion, these results suggest that NGC 3256 is the product of a multiple merger, which generated an extended massive star formation process with an associated galactic wind plus a nuclear inflow. Therefore, NGC 3256 is another example in which the relation between mergers and extreme starburst (and the powerful galactic wind, multiple Type II supernova explosions) play an important role in the evolution of galaxies (the hypothesis of Rieke et al., Joseph et al., Terlevich et al., Heckman et al., and Lipari et al.).

A SAMPLE OF SEYFERT-2 GALAXIES WITH ULTRALUMINOUS GALAXY-WIDE NARROW-LINE REGIONS: QUASAR LIGHT ECHOES?*

We report the discovery of Seyfert-2 galaxies in SDSS-DR8 with galaxy-wide, ultraluminous narrow-line regions (NLRs) at redshifts z = 0.2-0.6. With a space density of 4.4 Gpc?3 at z ~ 0.3, these green beans (GBs) are amongst the rarest objects in the universe. We are witnessing an exceptional and/or short-lived phenomenon in the life cycle of active galactic nuclei (AGNs). The main focus of this paper is on a detailed analysis of the GB prototype galaxy J2240?0927 (z = 0.326). Its NLR extends over 26 ? 44 kpc and is surrounded by an extended NLR. With a total [O III] ?5008 luminosity of (5.7 ? 0.9) ? 1043 erg s?1, this is one of the most luminous NLRs known around any type-2 galaxy. Using VLT/XSHOOTER, we show that the NLR is powered by an AGN, and we derive resolved extinction, density, and ionization maps. Gas kinematics is disturbed on a global scale, and high-velocity outflows are absent or faint. This NLR is unlike any other NLR or extended emission line region known. Spectroscopy with Gemini/GMOS reveals extended, high-luminosity [O III] emission also in other GBs. WISE 24 ?m luminosities are 5-50 times lower than predicted by the [O III] fluxes, suggesting that the NLRs reflect earlier, very active quasar states that have strongly subsided in less than a galaxys light-crossing time. These light echoes, or ionization echoes, are about 100 times more luminous than any other such echo known to date. X-ray data are needed for photoionization modeling and to verify the light echoes.

Infrared mergers and infrared quasi-stellar objects with galactic winds – II. NGC 5514: two extranuclear starbursts with LINER properties and a supergiant bubble in the rupture phase

A study of the morphology, kinematics and ionization structure of the IR merger NGC5514, is here presented. This study is based mainly on INTEGRAL twodimensional (2D) spectroscopy (obtained at the 4.2 m William Herschel Telescope, WHT), plus optical and near IR images. Clear evidence of two extra-nuclear starbursts with young outflows (OFs) and LINER activity are reported. One of these OFs has generated a supergiant bubble and the other is associated with an extended complex of H ii region. In the galactic bubble it was found that: (i) the [S ii], H�, [N ii], [O i] and [O iii] emission line maps show a bubble with a distorted ellipsoidal shape, with major and minor axes of �6.5 kpc (13.

Open clusters or their remnants: B and V photometry of NGC 1901 and NGC 1252

Photometry in theB andV bands is presented for the southern stellar groups NGC 1901 and NGC 1252. NGC 1901 is often described as an open cluster while NGC 1252 consists of a concentration of about 20 stars centered20 0 north of the original New General Catalogue coordinates, and at the southwest edge of the large region previously assigned to this object in the literature. NGC 1901 has a clear main sequence and shares similarities with the Hyades. We derive a reddening value E(B V )=0 :04, a distance from the Sund =0 :45 kpc (Z = 0:23 kpc) and an age 0.6 0.1 Gyr. NGC 1901 is conclusively a physical system, dynamically comparable to or more evolved than the Hyades. The colour-magnitude diagram of NGC 1252 suggests a turno and main sequence, and a total of 12 probable members. We simulated the Galactic eld colour-magnitude diagram in the same direction and found it to be a poor match to NGC 1252, suggesting that NGC 1252 is not a eld fluctuation. Isochrone tting to the probable members is consistent with E(B V )=0 :02, d =0 :64 kpc (Z = 0:46 kpc) and an age 3 1 Gyr. NGC 1252 cannot be ruled out as a physical group with the available data. If so, evidence is found that it is not a classical open cluster, but rather an open cluster remnant.

The nearest extreme starburst: bubbles, young star clusters and outflow in the merger NGC 3256

We have studied the extreme starburst in the infrared merger NGC 3256. We detect four galactic bubbles (using ESO New Technology Telescope and Hubble Space Telescope WFPC2 Hα images). These shells would be associated with previous supernova explosions. n n n nThe first analysis of the spatial distribution of young star cluster candidates shows that more than 90 per cent of them are located in a complex starburst structure, including some of the bubble walls, three nuclei and three blue asymmetrical spiral arms. n n n nWe have made a kinematic study of the ionized gas in the core of the main optical nucleus, performed with HST STIS spectra. The shape of the rotation curve and the emission-line profile can be explained by the presence in the core of young star clusters with outflow. Any low-luminosity active galactic nucleus associated with this core would have a mass less than 107 M⊙. It is also probable that the compact X-ray and radio emission of ULX(7)N – the source coincident with the main optical nucleus – is the result of a few recent supernova remnants.

Kinematics and modeling of the inner region of M 83

Two-dimensional kinematics of the central region of Mxa083 (NGCxa05236) were obtained through three-dimensional NIR spectroscopy with the Gemini South telescope. The spatial region covered by the integral field unit (~5 × 13 or ~90 × 240 pc) was centered approximately at the center of the bulge isophotes and oriented southeast-northwest. The Paβ emission at half-arcsecond resolution clearly reveals spider-like diagrams around three centers, indicating the presence of extended masses, which we describe in terms of Satoh distributions. One of the mass concentrations is identified as the optical nucleus (ON), another as the center of the bulge isophotes, similar to the CO kinematical center (KC), and the third as a condensation hidden at optical wavelengths (hidden nucleus, HN), coincident with the largest lobe in 10xa0μm emission. We run numerical simulations that take into account ON, KC, and HN and four more clusters, representing the star-forming arc at the southwest of the optical nucleus. We show that ON, KC, and HN suffer strong evaporation and merge in 10-50 Myr. The star-forming arc is scattered in less than one orbital period, also falling into the center. Simulations also show that tidal striping boosts the external shell of the condensations to their escape velocity. This fact might lead to an overestimation of the mass of the condensations in kinematical observations with spatial resolution smaller than the condensations apparent sizes. Additionally, the existence of two ILR resonances embracing the chain of Hxa0II regions, claimed by different authors, might not exist due to the similarity of the masses of the different components and the fast dynamical evolution of Mxa083 central 300xa0pc.

Study of McLeish’s Interacting Object

We discuss the morphology, kinematics, and physical conditions of the emitting gas of the interacting system IRAS 20048-6621. We present as well numerical simulations of this interacting system, discovered by David McLeish in 1946. The main galaxy (McL A) is an edge-on spiral galaxy with highly distorted NW side. On this side is also located McL B, the perturber galaxy. We determined a distance of 151 Mpc (h = 0.75) and a diameter of 70 kpc for McL A. It presents a bright nucleus with broad red emission lines (FWHM ≈ 500 km s-1). McL A has far-IR color indexes closely comparable to NGC 3628, one the few nearby edge-on galaxies which is a bright infrared emitter. Nevertheless, McL A is more luminous (in these bands) than any of the edge-on galaxies in the sample of bright infrared galaxies of Young et al. (1988). The two sides of McL A rotation curve are remarkably different. The N-body model that best reproduces McL A kinematical and morphological data (Kuijken &Dubinski 1995) gives a total mass 7 × 1011 M⊙ for McL A. Numerical simulations with the TREESPH code closely reproduce the morphology and radial velocity observations. The best scenario for this system is that of a prograde encounter between McL A and B, with McL Bs orbit 35° tilted with respect to the spiral disk of McL A and a perigalactic distance of 17.6 kpc. The derived mass ratio is McL B/McL A ≈ 1/26. In the last 5 × 108 yr the perturber has crossed the main galaxy disk twice, in between it crossed the perigalacticon. According to our simulations, the emitting gas present in McL B has not been stripped out from the McL A disk, so that leads us to conclude that McL B is an irregular or small spiral galaxy.

Differences between CO- and calcium triplet-derived velocity dispersions in spiral galaxies: evidence for central star formation?

We examine the stellar velocity dispersions (sigma) of a sample of 48 galaxies, 35 of which are spirals, from the Palomar nearby galaxy survey. It is known that for ultra-luminous infrared galaxies (ULIRGs) and merger remnants thesigma derived from the near-infrared CO band-heads is smaller than that measured from optical lines, while no discrepancy between these measurements is found for early-type galaxies. No such studies are available for spiral galaxies - the subject of this paper. We used cross-dispersed spectroscopic data obtained with the Gemini Near-Infrared Spectrograph (GNIRS), with spectral coverage from 0.85 to 2.5um, to obtain sigma measurements from the 2.29

IS J 133658.3-295105 A RADIO SOURCE AT z ⩾ 1.0 OR AT THE DISTANCE OF M 83?

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Separating C Stars from Dust in the Central Region of the Seyfert 2 Galaxy NGC 1241

m CO band-heads (sigma_{CO}), and the 0.85 um calcium triplet (sigma_{CaT}). For the spiral galaxies in the sample, we found that sigma_{CO} is smaller than sigma_{CaT}, with a mean fractional difference of 14.3%. The best fit to the data is given by sigma_{opt} = (46.0+/-18.1) + (0.85+/-0.12)sigma_{CO}. This sigma discrepancy may be related to the presence of warm dust, as suggested by a slight correlation between the discrepancy and the infrared luminosity. This is consistent with studies that have found no sigma-discrepancy in dust-poor early-type galaxies, and a much larger discrepancy in dusty merger remnants and ULIRGs. That sigma_{CO}