Emission-line Maps Research Articles

Atomic T Tauri disk winds heated by ambipolar diffusion

Thermal and ionization structures of self-similar, magnetically-driven disk winds obtained in a companion paper (Garcia et al. [CITE]) are used to compute a series of jet synthetic observations. These include spatially resolved forbidden line emission maps, long-slit spectra, as well as line ratios. Line profiles and jet widths appear to be good tracers of the wind dynamics and collimation, whereas line ratios essentially trace gas excitation conditions. All the above diagnostics are confronted to observations of T Tauri star microjets. Convolution by the observing beam is shown to be essential for a meaningful test of the models. We find that jet widths and qualitative variations in line profiles with both distance and line tracers are well reproduced. A low-velocity [Oi] component is also obtained, originating from the disk wind base. However, this component is too weak, predicted maximum velocities are too high and electronic and total densities are too low. Denser and slower magnetized winds, launched from disks with warm chromospheres, might resolve these discrepancies.

Integral Field Spectroscopy of Six Seyfert Galaxies

We summarize the main conclusions derived from integral field spectroscopy, with optical fibres, of six Seyfert galaxies. More than 95 spectra around the active nucleus have been obtained showing asymmetric emission-line profiles at different positions. Continuum and emission-line intensity maps and ionized gas velocity fields have been derived for these six galaxies. We also present the stellar velocity field for NGC 1068, NGC 3516 and NGC 985.

A Jet–Side Wind Interaction Model for the Curved Jets in the Orion Nebula

Bally & Reipurth have recently discovered a number of Herbig-Haro (HH) jets in the periphery of the Orion Nebula (M42). In many cases both these jets and their counterjets curve away from the central regions of M42. These curved outflows appear to be evidence of an interaction of the jets with an outward flow in the H II region. In this paper, we present three-dimensional gasdynamic models of HH jet–side wind interactions, showing that structures similar to those observed in the newly discovered jets are straightforwardly obtained. In particular, we concentrate on modeling the HH 505 jet and obtain one of the best agreements ever reported with gasdynamic models for emission-line maps of HH objects.

High‐Ionization Clouds in the Circumnuclear Region of M31

We present two-dimensional spectroscopy of the 125 × 125 pc2 circumnuclear region of M31, obtained using two optical fiber systems, INTEGRAL and 2D-FIS, installed at the 4.2 m William Herschel Telescope at the Roque de los Muchachos Observatory on the island of La Palma, Spain. We present continuum and emission-line maps, emission-line quotients, and stellar and ionized gas velocity fields obtained under subarcsecond seeing conditions. We have discovered Hβ, [O III] λλ4959, 5007, Hα, and [N II] λλ6548, 6584 emission in the inner 40 × 40 pc2 circumnuclear region. The intensity maps obtained from the emission lines show several isolated systems of ionized gas (clouds) a few parsecs in size. The kinematics of the clouds is decoupled from the stellar rotation, and strong radial motions are likely to be present. We have also discussed the ionization mechanisms present in the clouds. Although the emission-line quotients are compatible with ionization produced by post-asymptotic giant branch stars, the estimated ionization fluxes exceed what is expected according to the distribution of planetary nebulae in the bulge of M31. Comparison of the line quotients and spectra found in M31 with those found in the extended narrow-line region of the Seyfert galaxy NGC 4151 indicates that we could be in presence of ultralow-intensity nuclear activity. These results would be compatible with the existence of a dead quasar in the nucleus of M31 and underline the hybrid character of the LINER phenomenon.

The Extended Narrow‐Line Region of 3C 299

We present results of Hubble Space Telescope (HST) observations of the radio galaxy 3C 299. The broadband F702W (R) and F555W (V) images (WFPC2/PC) show an elliptical galaxy with a comet-like structure extending to the northeast in the radio jet direction. The [O III] λ5007 emission-line map shows a biconical structure centered on the nucleus, which overlaps the structure found in the broadband filters. The radio core coincides with the center of the biconical structure and the radio axes are aligned with the direction of the cones. These data show clear evidence of a strong interaction between the radio jet and the northeastern morphology of the galaxy. We show evidence that this northeast region is an extended narrow-line region (ENLR); the line-ratio diagnostics show that models involving gas shocked by the radio jet plus ionization from a precursor H II region—itself produced by the ionizing photons of the postshocked gas on the preshocked gas—provide a good match to the observations. We investigate the spatial behavior of the ionizing parameter U, by determining the [O III]/[O II] line ratio, which is sensitive to the change of the ionization parameter, and we trace its behavior over the ENLR along the radio jet direction. We find that [O III]/[O II] does not follow a simple dilution model, but rather it is approximately constant over a large range of distance from the nucleus, thus requiring a local source of ionization, which seems to be compatible with the shock models driven by the radio jet.

Dust Lanes Causing Structure in the Extended Narrow‐Line Region of Early‐Type Seyfert Galaxies

We construct near-infrared to visible broadband NICMOS/WFPC color maps for four early-type Seyfert galaxies with S-shaped or one-sided ionization cones. We find that dust lanes are near or connected to many of the features seen in the [O III] and H? + [N II] line emission maps. This suggests that much of the structure of line emission in these ionization cones is determined by the distribution of ambient dense galactic gas. Spiral arms, dust lanes caused by bars, or gaseous warps provide dense gas, which when illuminated by a conical beam of ultraviolet photons can result in the complicated line emission morphologies observed.

The Structure and Morphology of the Ionized Gas in Starburst Galaxies: NGC 5253/5236

We investigate the interplay between starbursts and host galaxies by studying the structure and physical characteristics of the ionized gas surrounding the central starbursts in the two nearby galaxies NGC 5253 and NGC 5236. The two systems form a pair that presumably interacted about 1 Gyr ago. They represent very different galactic environments, NGC 5253 being a metal-poor dwarf and NGC 5236 being a metal-rich, massive, grand-design spiral. We present images of the starburst regions in these two galaxies in the light of the line emission [O III], H?, and [S II] and in continuum U, V, and R. For NGC 5253, the images are deep enough that we can detect faint H? arches and filaments out to ~1.9 kpc and [S II] filaments out to ~1 kpc from the main ionizing cluster. The ground-based line images are complemented with an archival HST Wide Field Planetary Camera 2 H? image. Line ratio maps [O III]/H? and [S II]/H? show that in the outer regions the diffuse ionized gas is partially excited by a nonphotoionization process (shocks). The shocked gas is mostly concentrated southwest of the galaxy's center, in coincidence with the position of H? bubbles and with extended soft X-ray emission. The H? emission from the shock-excited gas is ?1%?2% of the total and ?10%?20% of the diffuse ionized gas emission, although the mechanical input from the starburst would be sufficient to support a shocked H? luminosity ~3 times the observed one. About 80%?90% of the diffuse gas is consistent with being photoionized, requiring that about 10% of the ionizing photons escape from the starburst site. The starburst in NGC 5253 appears to be fed by gas infalling along the galaxy's optical minor axis, while hot gas expanding from the starburst has a preferential direction along the major axis. The results for NGC 5236 are less clear than for NGC 5253, as the images are not as deep. In the central region of NGC 5236, the H? image traces the U emission from the ionizing stars more closely than in NGC 5253; the emission-line ratio maps show very little or no evidence for presence of shock excitation. Very little or no ionized gas appears expanding from the center of the galaxy outward along the disk plane, and ionization is a local process. The starburst in NGC 5236 is thus more strongly confined than that in NGC 5253; the deeper gravitational-potential well of the more massive galaxy probably keeps the ionized gas near to the ionizing stars.

L1448 IRS 2: A HIRES‐identified Class 0 Protostar

We present far-infrared and submillimeter images and millimeter-continuum photometry for L1448 IRS 2, a low-luminosity (5.2 L☉), embedded young stellar object discovered by IRAS. New far-infrared maps were produced from the archival IRAS data via high-resolution (HIRES) processing, the name given to the implementation of the maximum correlation method for image construction from the IRAS data streams. The HIRES-processed images of L1448 IRS 2 presented here have effective resolutions of ~35'' × 28'', ~35'' × 37'', and ~45'' × 40'' at 25, 60, and 100 μm, respectively, which represent an order of magnitude improvement over previously available far-infrared maps. L1448 IRS 2 was mapped at 450 and 850 μm, and we acquired continuum photometry at 1.3 mm. With these new data, we plot the most complete spectral energy distribution for L1448 IRS 2 to date. We also present sensitive 12CO J=1→0 emission-line maps of a 47' × 7' area of the L1448 dark cloud, centered on L1448 IRS 2, obtained with the on-the-fly imaging capability of the NRAO 12 m telescope. As a direct consequence of this mapping, we have discovered a parsec-scale molecular outflow associated with L1448 IRS 2. The combined continuum and molecular line data confirm the classification of L1448 IRS 2 as a new member of the rare, short-lived (a few × 104 yr), Class 0 phase of protostellar evolution. The use of HIRES imaging of IRAS data as a promising tool for identifying protostellar candidates is demonstrated by the example of L1448 IRS 2.

The “Water-Fountain Nebula” IRAS 16342−3814: [ITAL]Hubble Space Telescope[/ITAL]/Very Large Array Study of a Bipolar Protoplanetary Nebula

We present Hubble Space Telescope (HST) Wide-Field Planetary Camera 2 images and VLA OH maser emission-line maps of the cold infrared object IRAS 16342-3814, believed to be a protoplanetary nebula. The HST images show an asymmetrical bipolar nebula, with the lobes separated by a dark equatorial waist. The two bright lobes and the dark waist are simply interpreted as bubble-like reflection nebulae illuminated by starlight escaping through polar holes in a dense, flattened, optically thick cocoon of dust, which completely obscures the central star. A faint halo can be seen surrounding each of the lobes. The bubbles are likely to have been created by a fast outflow (evidenced by H2O emission) plowing into a surrounding dense, more slowly expanding, circumstellar envelope of the progenitor asymptotic giant-branch (AGB) star (evidenced by the halo). The IRAS fluxes indicate a circumstellar mass of about 0.7 solar mass (D/2 kpc) and an AGB mass-loss rate of about 10(exp -4) solar mass/yr (V(sub exp)/15 km/s)(D/2 kpc)(sup 2) (assuming a gas-to-dust ratio of 200). OH features with the largest redshifted and blueshifted velocities are concentrated around the bright eastern and western polar lobes, respectively, whereas intermediate-velocity features generally occur at low latitudes, in the dark waist region. We critically examine evidence for the post-AGB classification of IRAS 16342-3814.

A tangentially viewing vacuum ultraviolet TV system for the DIII–D divertor

A video camera system capable of imaging vacuum ultraviolet emission in the 120–160 nm wavelength range, from the entire divertor region in the DIII–D tokamak, was designed. The new system has a tangential view of the divertor similar to an existing tangential camera system [M. E. Fenstermacher et al., Rev. Sci. Instrum. 68, 974 (1997)] which has produced two-dimensional maps of visible line emission (400–800 nm) from deuterium and carbon in the divertor region. However, the overwhelming fraction of the power radiated by these elements is emitted by resonance transitions in the ultraviolet, namely the C IV line at 155.0 nm and Ly-α line at 121.6 nm. To image the ultraviolet light with an angular view including the inner wall and outer bias ring in DIII–D, a six-element optical system (f/8.9) was designed using a combination of reflective and refractive optics. This system will provide a spatial resolution of 1.2 cm in the object plane. An intermediate UV image formed in a secondary vacuum is converted to the visible by means of a phosphor plate and detected with a conventional charge injection device (CID) camera (30 ms framing rate). A single MgF2 lens serves as the vacuum interface between the primary and secondary vacuums; a second lens must be inserted in the secondary vacuum to correct the focus at 155 nm. Using the same tomographic inversion method employed for the visible TV, we will reconstruct the poloidal distribution of the UV divertor light. The grain size of the phosphor plate and the optical system aberrations limit the best focus spot size to 60 μm at the CID plane. The optical system is designed to withstand 350 °C vessel bakeout, 2 T magnetic fields, and disruption-induced accelerations of the vessel.

Molecular gas associated with Wolf-Rayet ring nebulae

We present the first 12CO 1→0 emission-line maps of the vicinities of two Wolf-Rayet stars (WR 16 and WR 75) and their associated ring nebulae. We illustrate that sizeable amounts of molecular gas appear associated with these ring nebulae and therefore that the mass of gas in ring nebulae is significantly higher than inferred from observations of the ionized gas component alone. We discuss the possible stellar and interstellar origins of these molecular materials and the implications for the evolution of massive stars up to the WR phase.

Chromospheric emission line mapping

Throughout its eighteen years of operation, the International Ultraviolet Explorer has afforded us the opportunity to make many new discoveries regarding the nature of the outer atmospheres of magnetically active, late-type stars. High-resolution spectra obtained continuously throughout the rotational cycle of rapidly-rotating stars have been used to map the spatial structure of the magnetic active regions in stellar chromospheres. The RS CVn-type binary system AR Lacertae has been observed intensively at 3 epochs, with additional observations with less complete phase coverage was obtained at 4 other epochs. Taken together, we are able to probe the evolution of atmospheric structure of AR Lac over a 13-year timeline. I briefly review techniques of chromospheric emission line mapping, and I summarize the IUE results for AR Lac, V711 Tau, EI Eri, V1794 Cyg, and TY Pyx. I conclude with a description of chromospheric imaging programs (present and future) that make use of the Hubble Space Telescope.

Imaging Spectrophotometry of the Orion Nebula Core. I. Emission-Line Mapping and Physical Conditions: Erratum

Imaging Spectrophotometry of the Orion Nebula Core. I. Emission-Line Mapping and Physical Conditions: Erratum

Imaging Spectrophotometry of the Ring Nebula

We present new results from a program of emission-line imaging spectrophotometry of planetary nebulae using the Ohio State University Imaging Fabry-Perot Spectrograph (IFPS). High-quality emission-line maps of the important diagnostic lines [NII]λλ5755,6583, [SII]λλ6717,6731, [OI]λ6300, [OIII]λ5007, Hα, and Hβ have been obtained. Maps of the ionization structure ([S II]/Hα, [N II]/Hα, [O III]/Hβ, and [O I]/[O III]), temperature in the N+ region, density in the S+ region, and Balmer decrement across the nebula are presented. These show considerable variation in ionization state, temperature and density. This detailed information will provide powerful constraints on photoionization models for the Ring Nebula.

Imaging spectrophotometry of the Orion Nebula core. I - Emission-line mapping and physical conditions

The results or a Fabry-Perot imaging spectrophotometric study of the core of the Orion Nebula H II region are presented. Hα, Hβ, [O III] λλ5007, [N II] λλ6548, 6583, [S II] λλ6716, 6731, and He I λ6678 emission-line flux maps have been derived from low-resolution (5 A FWHM) Fabry-Perot CCD interferograms of the inner 6' surrounding the exciting star θ 1 C Ori. From these fluxes were derived maps of the principal emission-line diagnostic ratios of [N II] λ6583/Hα, [O III] λ5007/Hβ, [S II] λλ6716+31/Hα, Hα/Hβ, [S II] λ6716/λ6731 and He I λ6678/Hα

Global O VI line emission from the Cygnus Loop supernova remnant and direct kinematic measurement of the associated shock

A far-ultraviolet spectrophotometric emission-line mapping of the Cygnus Loop supernova remnant is presented. These are results from the first flight of the rocket-borne, High Resolution Emission Line Spectrometer. The spatial distribution of the emission is that of a limb-brightened shell, and similar to soft X-ray maps. The emission-line profiles, which are broader than the instrument resolution, were consistent with uniformly expanding shell models. Best-fit values give a radial expansion velocity to the emissive region of 185(+/-19) km/s and a reddening-corrected average surface brightness of 8.8(+/-3.6) x 10 exp -6 ergs/sq cm s sr in the doublet. Comparison of the observed brightness with predictions of both radiative and nonradiative shock models provides constraints for the global blast wave ram pressure as well as a "covering factor" of the intermediate velocity shock.

Chemistry in circumstellar disks - CS toward HL Tauri

High spatial and spectral resolution dust continuum and CS line-emission maps of the material immediately surrounding HL Tauri are presented. The 3.06-thermal dust map gives an upper limit to the source size of roughly 200 AU. When combined with previous millimeter continuum measurements, a beta value of 1.2 +/-0.3 is derived along with a disk mass of 0.1 solar mass, in agreement with previous disk radiative transfer models of the IR and submillimeter flux from HL Tau. The low dust emissivity index as compared to particles in the diffuse ISM is best explained by grain growth or composition evolution. The present observations of the CS and CO emission lines forming the molecular cloud surrounding HL Tauri are consistent with the 'canonical' temperatures, densities, and abundances derived in other Taurus cloud cores. In contrast, the CS emission in aperture synthesis maps at 650-AU spatial resolution is most consistent with CS/CO ratios at least 25-50 times lower in the gas immediately surrounding HL Tauri if the CS emission is optically thin. The continuum and spectral line results obtained are strong indicators of conditions thought to be similar to those in the presolar nebula some 4.5 AE ago.

Mapping bow shocks in molecular hydrogen

Near-infrared imaging of Herbig-Haro objects in molecular clouds is now possible. Here, an attempt is made to simulate the H 2 emission-line maps with a model in which the H 2 emission is generated from a cool C-shock region in the oblique tail of a bow shock. It is shown that low-speed bows produce arcs and limb-brightened structures of conical appearance. High-speed bows yield more diffuse, tailed regions with blunter leading edges.

DIFFUSE IONIZED MEDIUM IN NGC 1068

ABSTRACT (~10 kpc; ~135"), diffuse ionized medium (DIM) recently detected in the nearby, luminous Seyfert galaxy NGC 1068. The DIM phase was recognized from spectrophotometric Hα and [N II] λλ6548,6584 line emission maps obtained with the Hawaii Imaging Fabry-Perot Interferometer (HIFI). We demonstrate that the Hot equivalent-width distribution, when combined with the [N II] λ6584/Hα line ratio distribution, permits a clean separation of the DIM from the adjacent H II region population. We summarize the main reasons that lead us to believe the DIM is photoexcited predominantly by scattered light from the active nucleus rather than the extended stellar population.

Emission-line mapping of the dwarf nova IP Pegasi in outburst and quiescence

Time-resolved spectroscopy covering half an orbit and one eclipse during an outburst of the dwarf nova IP Peg are presented and compared with quiescent data. The outburst spectra show strong Balmer and He II 4686 A emission lines that are atypical of outbursting dwarf novae. Double-peaked velocity profiles and rotational distortions during eclipse show that the lines arise primarily in a Keplerian accretional disk. The He II line profile is filled in between the two disk peaks by non-Keplerian emission from close to the white dwarf, possibly indicative of a compact outflowing wind or inflowing magnetic accretion column. During outburst, an accretion rate of roughly 10 to the 17th g/s is needed to acccount for the continuum emission of the disk. The associated boundary layer generates soft X-ray and Lyman continuum fluxes sufficient to photoionize the disk's He II and Balmer emission-line regions. The disk appears to shield the red star totally from the soft X-rays, and in the equatorial region, from the Lyman continuum. 46 refs.