arXiv subjects
Publications and source records attributed to S. Veilleux.
We report on optical and near-infrared (NIR) follow-up spectroscopy of faint far-infrared (FIR) sources found in our deep FIR survey by Kawara et al.
The preliminary results from a deep emission-line search for warm ionized material in the halos of nearby active and star-forming galaxies are presented. The origin of this gas is discussed in the context of galaxy formation and evolution.
We report a new Fabry-Perot search for Halpha emission from the intergalactic cloud HI 1225+01 in an attempt to measure the low redshift ionizing background radiation. We set a new 2 sigma upper limit on Halpha emission of 8 mR (5 x 10^{-20} ergs cm^{-2} s^{-1} arcsec^{-2}). Conversion of this limit to limits on the strength of the ionizing background requires knowledge of the ratio of the projected to total surface area of this cloud, which is uncertain. We discuss the plausible range of this ratio, and within this range find that the strength of the ionizing backround is in the lower range of, but consistent with, previous observational and theoretical estimates.
For the past several years, our group has pursued a vigorous ground-based program aimed at understanding the nature of ultraluminous infrared galaxies. We recently published the results from a optical/near-infrared spectroscopic survey of a large statistically complete sample of ultraluminous infrared galaxies (the "IRAS 1-Jy sample"). We now present the results from our recently completed optical/near-infrared imaging survey of the 1-Jy sample. These data provide detailed morphological information on both large scale (e.g., intensity and color profiles, intensity and size of tidal tails and bridges, etc) and small scale (e.g., nuclear separation, presence of bars, etc) that helps us constrain the initial conditions necessary to produce galaxies with such high level of star formation and/or AGN activity. The nature of the interdependence between some key spectroscopic and morphological parameters in our objects (e.g., dominant energy source: super-starburst versus quasar, nuclear separation, merger phase, star formation rate, and infrared luminosity and color) is used to clarify the connection between starbursts, ultraluminous infrared galaxies, and quasars.
Recent results from a multiwavelength survey of spatially resolved outflows in nearby active galaxies are presented. Optical Fabry-Perot and long-slit spectroscopic data are combined with VLA and ROSAT images, when available, to probe the warm, relativistic and hot gas components involved in the outflow. The emphasis is put on objects which harbor wide-angle galactic-scale outflows but also show evidence at radio or optical wavelengths for collimated jet-like phenomena (e.g., Circinus, NGC 4388, and to a lesser extent NGC 2992). Our results are compared with the predictions from published jet-driven thermal wind models.
HST WFPC2 images are presented that span the inner 19 kpc diameter of the edge-on spiral galaxy NGC 3079; they are combined with ground-based Halpha+[N II] Fabry-Perot spectra and VLA images of radio polarization vectors and rotation measures. Ionized gas filaments within 9 kpc diameter project ~3 kpc above the disk, with the brightest forming the 1 kpc diameter superbubble. They are often resolved into strands ~0."3 (25 pc) wide which emerge from the nuclear CO ring as five distinct gas streams with velocity gradients and dispersions of hundreds of km/s. One stream flows for 250 pc and aligns with the VLBI-scale radio jet, the other four are not connected to the jet, instead curving to the vertical 0.6 kpc above the galaxy disk, then dispersing in a spray of droplets each with ionized mass ~1000 sqrt(f) Msun (volume filling factor f > 0.003 from our data). Shredded clumps of disk gas form a similar structure in hydro models of a galaxy-scale wind. The pattern of magnetic fields and the gas kinematics also suggest a wind of mechanical luminosity 10^43 erg/s that has stagnated in the galaxy disk at radius ~800 pc, flared to larger radii with increasing height as the balancing ISM pressure reduces above the disk, and entrained dense clouds into a vortex. Total KE and momentum of the filaments are (0.4-5)x10^55 sqrt(f) ergs and (1.6-6)x10^47 sqrt(f) dyne s. A star-forming complex elsewhere in the galaxy shows a striking spray of linear filaments that extend for hundreds of parsecs.
We present contemporary infrared and optical spectroscopic observations of the type IIn SN 1998S for the period between 3 and 127 days after discovery. In the first week the spectra are characterised by prominent broad emission lines with narrow peaks superimposed on a very blue continuum(T~24000K). In the following two weeks broad, blueshifted absorption components appeared in the spectra and the temperature dropped. By day 44, broad emission components in H and He reappeared in the spectra. These persisted to 100-130d, becoming increasingly asymmetric. We agree with Leonard et al. (2000) that the broad emission lines indicate interaction between the ejecta and circumstellar material (CSM) and deduce that progenitor of SN 1998S appears to have gone through at least two phases of mass loss, giving rise to two CSM zones. Examination of the spectra indicates that the inner zone extended to <90AU, while the outer CSM extended from 185AU to over 1800AU. Analysis of high resolution spectra shows that the outer CSM had a velocity of 40-50 km/s. Assuming a constant velocity, we can infer that the outer CSM wind commenced more than 170 years ago, and ceased about 20 years ago, while the inner CSM wind may have commenced less than 9 years ago. During the era of the outer CSM wind the outflow was high, >2x10^{-5}M_{\odot}/yr corresponding to a mass loss of at least 0.003M_{\odot} and suggesting a massive progenitor. We also model the CO emission observed in SN 1998S. We deduce a CO mass of ~10^{-3} M_{\odot} moving at ~2200km/s, and infer a mixed metal/He core of ~4M_{\odot}, again indicating a massive progenitor.
We report on a detailed kinematic study of the galactic-scale outflow in the Seyfert galaxy NGC 2992. The TAURUS-2 Imaging Fabry-Perot Interferometer was used on the Anglo-Australian 3.9-m telescope to derive the two-dimensional velocity field of the Halpha-emitting gas over the central arcminute of NGC 2992. The complete two-dimensional coverage of the data combined with simple kinematic models of rotating axisymmetric disks allows us to differentiate the outflowing material from the line-emitting material associated with the galactic disk. The kinematics of the disk component out to R = 3.0 kpc are well modeled by pure circular rotation. The outflow component is distributed into two wide cones with opening angle of 125 -- 135 degrees and extending 2.8 kpc (18") on both sides of the nucleus at nearly right angles to the disk kinematic major axis. The outflow on the SE side of the nucleus is made of two distinct kinematic components interpreted as the front and back walls of a cone. The azimuthal velocity gradient in the back-wall component reflects residual rotational motion which indicates either that the outflowing material was lifted from the disk or that the underlying galactic disk is contributing slightly to this component. A single outflow component is detected in the NW cone. The most likely energy source for this outflow is a hot bipolar thermal wind powered on sub-kpc scale by the AGN and diverted along the galaxy minor axis by the pressure gradient of the ISM in the host galaxy. The data are not consistent with a starburst-driven wind or a collimated outflow powered by radio jets. (abridged)
We report -as a part of a long-term study of mergers and IR QSOs- detailed spectroscopic evidences for outflow (OF) and/or Wolf Rayet features in: (i) low velocity OF in the ongoing mergers NGC 4038/39 and IRAS 23128-5919; (ii) extreme velocity OF (EVOF) in the QSOs IRAS 01003-2238 and IRAS 13218+0552; (iii) OF and EVOF in a complete sample of ultra-luminous IR galaxies/QSOs ("The IRAS 1 Jy MKO-KPNO Survey", of 118 objects). We found EVOF in IRAS 11119+3257, 14394+5332, 15130+1958 and 15462-0450. The OF components detected in these objects were mainly associated to starburst processes: i.e., to galactic-winds generated in multiple type II SN explosions and massive stars. The EVOF were detected in objects with strong starburst plus obscured IR QSOs; which suggest that interaction of both processes could generate EVOF. In addition, we analyze the presence of Wolf Rayet features in the large sample of Bright PG-QSOs (Boroson and Green 1992), and nearby mergers and galactic-wind galaxies. We found clear WR features in the Fe II QSOs (type I): PG 1244+026, 1444+407, 1448+273, 1535+547; and in the IR merger Arp 220. HST archive images of IR+BAL QSOs show in practically all of these objects "arc or shell" features probably associated to galactic-winds (i.e., to multiple type II SN explosions) and/or merger processes. Finally, we discuss the presence of extreme starburst and galactic wind as a possible evolutive link between IR merger and IR QSOs; where the relation between mergers and extreme starburst (with powerful galactic-winds) plays in important role, in the evolution of galaxies.
We report the results of deep H-alpha imaging of the ionized gas surrounding the low-redshift (z=0.0638) quasar MR 2251-178 using the TAURUS Tunable Filter (TTF) on the Anglo-Australian Telescope. Our observations reach a 2-sigma detection level of ~5 x 10^-18 erg s^-1 cm^-2 arcsec^-2, more than an order of magnitude deeper than conventional narrowband images previously published on this object. Our data reveal a spiral complex that extends more or less symmetrically over ~200 kpc, making it the largest known quasar nebula. The total mass of ionized gas is 6 x 10^10 solar masses (upper limit), a large fraction of which is in a very faint, diffuse component. The large and symmetric extent of the gaseous envelope favors a model in which the filamentary and diffuse emission arises from a large cloud complex, photoionized by the bright quasar. A crude kinematic analysis reveals relatively smooth rotation, suggesting that the envelope did not originate with a cooling flow, a past merger event, or an interaction with the nearby galaxy G1.
We present direct kinematic evidence for bar streaming motions in two active galaxies with boxy stellar bulges. The Hawaii Imaging Fabry-Perot Interferometer was used on the Canada-France-Hawaii 3.6-m telescope and the University of Hawaii 2.2-m telescope to derive the two-dimensional velocity field of the line-emitting gas in the disks of the Sc galaxy NGC 3079 and the Sb galaxy NGC 4388. In contrast to previous work based on long-slit data, the detection of the bar potential from the Fabry-Perot data does not rely on the existence of inner Lindblad resonances or strong bar-induced shocks. Simple kinematic models which approximate the intrinsic gas orbits as nonintersecting, inclined elliptical annuli that conserve angular momentum characterize the observed velocity fields. Box-shaped bulges in both NGC 3079 and NGC 4388 are confirmed using new near-infrared images to reduce dust obscuration. Morphological analysis of starlight in these galaxies is combined with the gas kinematics derived from the Fabry-Perot spectra to test evolutionary models of stellar bars that involve transitory boxy bulges, and to quantify the importance of such bars in fueling active nuclei. Our data support the evolutionary bar models, but fail to prove convincingly that the stellar bars in NGC 3079 and NGC 4388 directly trigger or sustain the nuclear activity. (abridged)
To date, the most detailed studies of galactic winds have come from 3-D spectrophotometric observations with radio and Fabry-Perot interferometers. Here, we report the latest results from a long-term optical survey of nearby active and starburst galaxies with the Hawaii Imaging Fabry-Perot Interferometer (HIFI) at Mauna Kea and the TAURUS-2 system in Australia. These data reveal that the outflows are highly complex, highly energetic (> 10^{53} ergs in most cases), and the brightest emission often appears to be associated with strong shocks. The outflowing material in the starburst galaxies generally lies on the surface of bubbles or along the walls of funnel-shaped winds rapidly accelerating out of the galactic plane. These winds are sometimes lop-sided and tilted with respect to the polar axis of the host galaxy. Evidence for entrainment of (rotating) disk material is seen in some objects. Our results are combined with HST, radio and X-ray data and discussed in the context of future surveys of distant galaxies on 8-meter class telescopes.
This paper discusses the optical spectroscopic properties of the IRAS 1-Jy sample of ultraluminous infrared galaxies (ULIGs). One hundred and eight of the 118 1-Jy ULIGs have been observed at dlambda = 8.3 AA resolution over the wavelength range ~4500 A -- 8900 A. These data are combined with large, previously published sets of optical spectroscopic data of lower luminosity infrared galaxies to look for systematic trends with infrared luminosity over the luminosity range L_ir ~ 10^{10.5}-10^{13} L_sun. As found in previous studies, the fraction of Seyfert galaxies among luminous infrared galaxies increases abruptly above L_ir ~ 10^{12.3} L_sun --- about 50% of the galaxies with L_ir > 10^{12.3} L_sun present Seyfert characteristics. Many of the optical and infrared spectroscopic properties of the Seyfert galaxies are consistent with the presence of a genuine active galactic nucleus (AGN). About 30% of these galaxies are Seyfert 1s with broad-line regions similar to those of optical quasars. The percentage of Seyfert 1 ULIGs increases with infrared luminosity, contrary to the predictions of the standard unification model for Seyfert galaxies. Comparisons of the broad-line luminosities of optical and obscured Seyfert 1 ULIGs with those of optically selected quasars of comparable bolometric luminosity suggest that the dominant energy source in most of these ULIGs is the same as in optical quasars, namely mass accretion onto a supermassive black hole, rather than a starburst. These results are consistent with recently published ISO, ASCA, and VLBI data. (abridged)
This paper reports the latest results from a near-infrared search for hidden broad-line regions (BLRs: FWHM >~ 2,000 km/s) in ultraluminous infrared galaxies (ULIGs). The new sample contains thirty-nine ULIGs from the 1-Jy sample selected for their lack of BLRs at optical wavelengths. The results from this new study are combined with those from our previous optical and near-infrared surveys to derive the fraction of all ULIGs with optical or near-infrared signs of genuine AGN activity (either a BLR or [Si VI] emission). Comparisons of the dereddened emission-line luminosities of the optical or obscured BLRs detected in the ULIGs of the 1-Jy sample with those of optical quasars indicate that the obscured AGN/quasar in ULIGs is the main source of energy in at least 15 -- 25% of all ULIGs in the 1-Jy sample. This fraction is 30 -- 50% among ULIGs with L_ir > 10^{12.3} L_sun. These results are compatible with those from recent mid-infrared spectroscopic surveys carried out with ISO. (abridged)
This paper reviews the results from recent optical and near-infrared spectroscopic studies of ultraluminous infrared galaxies.
New tools from Infrared Space Observatory (ISO) mid-infrared spectroscopy have recently become available to determine the power sources of dust-obscured ultraluminous infrared galaxies (ULIRGs). We compare ISO classifications - starburst or active galactic nucleus (AGN) - with classifications from optical spectroscopy, and with optical/near-infrared searches for hidden broad-line regions. The agreement between mid-infrared and optical classification is excellent if optical LINER spectra are assigned to the starburst group. The starburst nature of ULIRG LINERs strongly supports the suggestion that LINER spectra in infrared-selected galaxies, rather than being an expression of the AGN phenomenon, are due to shocks that are probably related to galactic superwinds. Differences between ISO and optical classification provide clues on the evolution of ULIRGs and on the configuration of obscuring dust. We find few ISO AGN with optical HII or LINER identification, suggesting that highly obscured AGN exist but are not typical for the ULIRG phenomenon in general. Rather, our results indicate that strong AGN activity, once triggered, quickly breaks the obscuring screen at least in certain directions, thus becoming detectable over a wide wavelength range.
The Hawaii Imaging Fabry-Perot Interferometer (HIFI) on the University of Hawaii 2.2m telescope was used to map the Halpha and [O III] 5007 A emission-line profiles across the entire disk of the edge-on Sb galaxy NGC 4388. We confirm a rich complex of highly ionized gas that extends ~4 kpc above the disk of this galaxy. Low-ionization gas associated with star formation is also present in the disk. Evidence for bar streaming is detected in the disk component and is discussed in a companion paper (Veilleux, Bland-Hawthorn, & Cecil 1999; hereafter VBC). Non-rotational blueshifted velocities of 50 - 250 km/s are measured in the extraplanar gas north-east of the nucleus. The brighter features in this complex tend to have more blueshifted velocities. A redshifted cloud is also detected 2 kpc south-west of the nucleus. The velocity field of the extraplanar gas of NGC 4388 appears to be unaffected by the inferred supersonic (Mach number M ~ 3) motion of this galaxy through the ICM of the Virgo cluster. We argue that this is because the galaxy and the high-|z| gas lie behind a Mach cone with opening angle ~ 80 degrees. The shocked ICM that flows near the galaxy has a velocity of ~ 500 km/s and exerts insufficient ram pressure on the extraplanar gas to perturb its kinematics. We consider several explanations of the velocity field of the extraplanar gas. Velocities, especially blueshifted velocities on the N side of the galaxy, are best explained as a bipolar outflow which is tilted by > 12 degrees from the normal to the disk. The observed offset between the extraplanar gas and the radio structure may be due to buoyancy or refractive bending by density gradients in the halo gas. Velocity substructure in the outflowing gas also suggests an interaction with ambient halo gas.
The Smith high velocity cloud (V(LSR) = 98 kms) has been observed at two locations in the emission lines [OIII]5007, [NII]6548 and H-alpha. Both the [NII] and H-alpha profiles show bright cores due to the Reynolds layer, and red wings with emission extending to V(LSR) = 130 kms. This is the first simultaneous detection of two emission lines towards a high velocity cloud, allowing us to form the ratio of these line profiles as a function of LSR velocity. At both cloud positions, we see a clear distinction between emission at the cloud velocity, and the Reynolds layer emission (V(LSR) = 0). The [NII]/H-alpha ratio (=0.25) for the Reynolds layer is typical of the warm ionised medium. At the cloud velocity, this ratio is enhanced by a factor of 3-4 compared to emission at rest with respect to the LSR. A moderately deep upper limit at [OIII] (0.12R at 3-sigma) was derived from our data. If the emission arises from dilute photoionisation from hot young stars, the highly enhanced [NII]/H-alpha ratio, the [OIII] non-detection and weak H-alpha emission (0.24-0.30R) suggest that the Smith Cloud is 26+/-4 kpc from the Sun, at a Galactocentric radius of 20+/-4 kpc. This value assumes that the emission arises from an optically thick slab, with a covering fraction of unity as seen by the ionizing photons, whose orientation is either (a) parallel to the Galactic disk, or (b) such as to maximize the received flux from the disk. The estimated mass and size of the cloud are 4x10^6 Msun and 6 kpc. We discuss a possible association with the much larger Sgr dwarf, at a galactocentric radius of 16+/-2 kpc, which lies within 35 degrees (~12 kpc) of the Smith Cloud.