Emission Knots Research Articles

Spitzerand Magellan Observations of NGC 2264: A Remarkable Star‐forming Core near IRS 2

We analyze {\it Spitzer} and Magellan observations of a star forming core near IRS-2 in the young cluster NGC 2264. The submillimeter source IRAS 12 S1, previously believed to be an intermediate mass Class 0 object is shown to be a dense collection of embedded, low mass stars. We argue that this group of stars represents the fragmenting collapse of a dense, turbulent core, based on a number of indicators of extreme youth. With reasonable estimates for the velocity dispersion in the group, we estimate a dynamical lifetime of only a few x 10$^{4}$ years. Spectral energy distributions of stars in the core are consistent with Class I or Class 0 assignments. We present observations of an extensive system of molecular hydrogen emission knots. The luminosity of the objects in the core region are consistent with roughly solar mass protostars.

X-rays from HH 210 in the Orion nebula

We report the detection during the Chandra Orion Ultradeep Project(COUP) of two soft, constant, and faint X-ray sources associated with the Herbig-Haro object HH 210. HH 210 is located at the tip of the NNE finger of the emission line system bursting out of the BN-KL complex, northwest of the Trapezium cluster in the OMC-1 molecular cloud. Using a recent Himage obtained with the ACS imager on board HST, and taking into account the known proper motions of HH 210 emis- sion knots, we show that the position of the brightest X-ray source, COUP 703, coincides with the emission knot 154-040a of HH 210, which is the emission knot of HH 210 having the highest tangential velocity (425 km s −1 ). The second X-ray source, COUP 704, is located on the complicated emission tail of HH 210 close to an emission line filament and has no obvious opti- cal/infrared counterpart. Spectral fitting indicates for both s ources a plasma temperature of∼0.8 MK and absorption-corrected X-ray luminosities of about 10 30 erg s −1 (0.5-2.0 keV). These X-ray sources are well explained by a model invoking a fast- moving, radiative bow shock in a neutral medium with a density of∼12000 cm −3 . The X-ray detection of COUP 704 therefore reveals, in the complicated HH 210 region, an energetic shock not yet identified at other wavelengths.

Imaging study of NGC 3372, the Carina nebula -- II. Evidence of activity in the complex Trumpler 14/Car I photodissociation region

We present the results of an imaging survey, from the optical to the mid-infrared, of the dark cloud associated with Car I, a dense cloud that is subject to an intense ultraviolet radiation field from the rich stellar cluster Trumpler 14. New ground-based broad- and narrowband near-infrared and narrow-band optical images are analysed in combination with archived Spitzer/InfraRed Array Camera (IRAC) images to study this photodissociation region (PDR) and the triggering of a new generation of stars within the cloud, particularly close to its edges. Evidence is given of a clumpy morphology of the dense cloud. The ionization/dissociation front is delineated at the edges of these clumps. The existence of a number of embedded lowto intermediate-mass pre-main-sequence objects is confirmed by their considerable infrared excesses arising from discs and/or detectable X-ray emission. Most of the young stellar objects (YSOs) are located on or just behind ionization fronts, though a few are also outside the cloud. The infrared properties of the YSOs are discussed. Two Class I objects stand out, one of them is an FU Orionis system candidate that had an outburst of more than 3 mag in K between 1993 and 2003, with further evidence that it occurred in the 2000‐02 period. Molecular hydrogen line filamentary emission behind the Balmer and Brackett lines along the ionization front is seen delineating the edges of the dense cloud. This emission is also seen in all IRAC images. The diffuse, filamentary emission is very similar in all four 3.6, 4.5, 5.8 and 8 μm bands, though there seem to be subtle differences. Across a bright section of the ionization/dissociation front, we found that, within the observational uncertainties, the maximum emission in all four IRAC channels coincides with that of H2 2.12 μm. The western, embedded, dissociation front close to the CO peak (Car I-W) is seen delineated by a bright, long bar of emission in the 3‐12 μm images, in the Midcourse Space Experiment bands A and C and also in radio continuum and hydrogen line emission. These occur in the vicinity of a region of previously reported strong [C I], [C II] and [O I] emission, tracers of PDRs. A few bright, compact knots of H2 emission, some possibly associated with [S II] emission, are found within the cloud. These may be shock-excited.

An archival study of extended X-ray emission from classical and recurrent novae

I discuss morphology and spectrum of the first resolved and detected classical nova shell in the X-rays – the remnant of GK Persei (1901). The existence of such a nebulosity brings about the possibility of other nova remnants emitting X-rays. I calculate that the X-ray luminosity should be about 10 26–10 33 ergs s −1 on the onset of cooling for nova remnants. I have done an archival search on 250 classical and recurrent nova candidates using Chandra, XMM-Newton, ROSAT and ASCA databases. There is no significant extended emission detected which places an upper limit of F x < × 10 −12 erg s −1 cm −2 (unabsorbed). Only exceptions are GK Per, RR Pic and DQ Her (all observed by Chandra ACIS-S and GK Per also by ROSAT HRI) where the latter two show marginal extended emission in the X-rays associated with emission knots (DQ Her) or an equatorial ring (RR Pic).

Supernova Remnants in the Magellanic Clouds. VI. The DEM L316 Supernova Remnants

The DEM L316 system contains two shells, both with the characteristic signatures of supernova remnants (SNRs). We analyze Chandra and XMM-Newton data for DEM L316, investigating its spatial and spectral X-ray features. Our Chandra observations resolve the structure of the northeastern SNR (shell A) as a bright inner ring and a set of arcs surrounded by fainter diffuse emission. The spectrum is well fit by a thermal plasma model with a temperature of ~1.4 keV; we do not find significant spectral differences for different regions of this SNR. The southwestern SNR (shell B) exhibits an irregular X-ray outline, with a brighter interior ring of emission including a bright knot of emission. Overall, the emission of the SNR is well described by a thermal plasma of temperature ~0.6 keV. The bright knot, however, is spectrally distinct from the rest of the SNR, requiring the addition of a high-energy spectral component consistent with a power-law spectrum of photon index 1.6-1.8. We confirm the findings of Nishiuchi and coworkers that the spectra of these shells are notably different, with shell A requiring a high iron abundance for a good spectral fit, implying a Type Ia origin. We further explicitly compare abundance ratios to model predictions for Type Ia and Type II supernovae. The low ratios for shell A (O/Fe of 1.5 and Ne/Fe of 0.2) and the high ratios for shell B (O/Fe of 30-130 and Ne/Fe of 8-16) are consistent with Type Ia and Type II origins, respectively. The difference between the SNR progenitor types casts some doubt on the suggestion that these SNRs are interacting with one another.

Chromospheric Evaporation in Solar Flares Revisited

We investigate the initial stage of chromospheric evaporation in flares using soft X-ray spectra obtained by the Bragg Crystal Spectrometer (BCS) experiment on Yohkoh. We find that the centroid wavelength of the Ca XIX line in spectra with the first detectable emission is within about 8.5 × 10-4 A of the rest wavelength, which corresponds to a Doppler shift of no more than 80 km s-1. We also determine the minimum detectable soft X-ray flare volume emission measure from BCS Ca XIX flare spectra. We find that the minimum detectable emission measured by BCS is produced by an X-ray flux that is about equal to the peak intensity of a class A6 flare. These results are difficult to reconcile with one-dimensional hydrodynamic simulations of an impulsively heated flare loop, which predict large Doppler shifts during the initial stage of the heating. Furthermore, inspection of high spatial resolution TRACE images of flare plasma indicate significant differences between the observed morphology and the predictions of hydrodynamic models. The evolution of the intensity and the Doppler shifts are more consistent with models that assume the sequential heating of small-scale threads rather than the heating of an individual loop. However, the bright knots of emission and asymmetrical intensity distributions seen in flare images cannot be explained by current numerical models of chromospheric evaporation.

A Survey of Massive Star Clusters in the X-ray Emission from Spiral Galaxies

The massive star clusters identified by S. Larsen are compared to the available Chandra observations of face-on spiral galaxies. In each galaxy, a few percent of the Larsen-identified clusters match X-ray-emitting point sources. An additional few match knots of emission in the diffuse emission. The cluster properties are examined to ascertain whether massive star clusters are X-ray sources.

Mapping the Kinematics of the Narrow-Line Region in the Seyfert Galaxy NGC 4151

Using the Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS), observations of the [O III] emission from the narrow-line region (NLR) of NGC 4151 were obtained and radial velocities determined. Five orbits of HST time were used to obtain spectra at five parallel slit configurations at a position angle of 58°, with spatial resolution 02 across and 01 along each slit. A spectral resolving power (Δλ/λ) of ~9000 with the G430M grating gave velocity measurements accurate to ~34 km s-1. A kinematic model was generated to match the radial velocities for comparison to previous kinematic models of biconical radial outflow developed for low-dispersion spectra at two slit positions. The new high-resolution spectra permit the measurement of accurate velocity dispersions for each radial velocity component. The FWHM reaches a maximum of 1000 km s-1 near the nucleus and generally decreases with increasing distance to about 100 km s-1 in the extended NLR, starting at about 6'' from the nucleus. In addition to the bright emission knots, which generally fit our model, there are faint high-velocity clouds that do not fit the biconical outflow pattern of our kinematic model. These faint clouds occur at the turnover points of the outflowing bright clouds. We suggest possible scenarios that could explain these rogue clouds: (1) backflow resulting from shocks and (2) outflow outside of the bicones, although the latter does not explain how the knots are ionized and accelerated. A comparison of our observations with a high-resolution radio map shows that there is no evidence that the kinematics of the NLR clouds are affected by the radio lobes that comprise the inner jet.

The Halo, Hot Spots, and Jet/Cloud Interaction of PKS 2153−69

We report Chandra X-ray Observatory and 1.4 GHz Australian Long Baseline Array (LBA) observations of the radio galaxy PKS 2153--69 and its environment. The Chandra image reveals a roughly spherical halo of hot gas extending out to 30 kpc around PKS 2153--69. Two depressions in the surface brightness of the X-ray halo correspond to the large scale radio lobes, and interpreting these as cavities inflated with radio plasma we infer a jet power of 4x10^42 erg/s. Both radio lobes contain hot spots that are detected by Chandra. In addition, the southern hot spot is detected in the 1.4 GHz LBA observation, providing the highest linear resolution image of a radio lobe hot spot to date. The northern hot spot was not detected in the LBA observation. The radio to X-ray spectra of the hot spots are consistent with a simple power law emission model. The nucleus has an X-ray spectrum typical of a type 1 active galactic nucleus, and the LBA observation shows a one-sided nuclear jet on 0.1 scales. Approximately 10 northeast of the nucleus, X-ray emission is associated with an extra-nuclear cloud. The X-ray emission from the cloud can be divided into two regions, an unresolved western component associated with a knot of radio emission (in a low resolution map), and a spatially extended eastern component aligned with the pc-scale jet and associated with highly ionized optical line-emitting clouds. The X-ray spectrum of the eastern component is very soft (Gamma > 4.0 for a power law model or kT ~0.22 keV for a thermal plasma). The LBA observation did not detect compact radio emission from the extra-nuclear cloud. (Abstract truncated).

Hubble Space Telescope NICMOS Imaging of W3 IRS 5: A Trapezium in the Making?

We present Hubble Space Telescope NICMOS imaging of W3 IRS 5, a binary high-mass protostar. In addition to the two protostars, NICMOS images taken in the F222M and F160W filters show three new 2.22 μm sources with very red colors; these sources fall within a region 5600 AU in diameter and are coincident with an ~100 M☉, dense molecular clump. Two additional point sources are found within 04 (800 AU) of one of the high-mass protostars; these may be stellar companions or unresolved emission knots from an outflow. We propose that these sources constitute a nascent Trapezium system in the center of the W3 IRS 5 cluster containing as many as five proto-OB stars. This would be the first identification of a Trapezium still deeply embedded in its natal gas.

New Silhouette Disks with Reflection Nebulae and Outflows in the Orion Nebula and M43

We report the detection of several new circumstellar disks seen in silhouette against background nebular light in the outskirts of the Orion Nebula and the neighboring H II region M43. These were detected as part of our Hα survey of Orion with the Advanced Camera for Surveys on board the Hubble Space Telescope. Several of the disks show bipolar reflection nebulae, microjets, or pronounced temporal variability of their central stars. The relatively large fraction of bipolar reflection nebulae and microjets in our sample may be a selection effect caused by the faint nebular background far from the Trapezium. Two disks in our sample are large and particularly noteworthy: A nearly edge-on disk, d216-0939, is located several arcminutes northwest of M43 and resembles the famous HH 30 disk/jet system in Taurus. It drives the 0.15 pc long bipolar outflow HH 667 and exhibits a remarkable asymmetric reflection nebula caused by the tilt of the flared disk. With a diameter of ∼26 (1200 AU), d216-0939 is as large as the giant edge-on silhouette disk d114-426 in the core of the Orion Nebula. The large disk d253-1536 is located in a binary system embedded within an externally ionized giant proplyd in M43. The disk exhibits distortions that we attribute to tidal interactions with the companion star. The bipolar jet HH 668 emerges from the proplyd ionization front in a direction orthogonal to the disk and can be traced to the young star embedded within it. A bow shock lies 54'' south of this binary system along the outflow axis. Proper motions over a 1.4 yr baseline confirm that these emission knots are indeed moving away from d253-1536 with speeds as high as ∼330 km s-1 in the HH 668 microjet and slower motion farther from the star.

A study of the Galactic star forming region IRAS 02593+6016/S 201 in infrared and radio wavelengths

We present infrared and radio continuum observations of the S 201 star forming region. A massive star cluster is seen, which contains different classes of young stellar objects. The near-infrared colour-colour and colour-magnitude diagrams are studied to determine the nature of these sources. We have discovered knots of molecular hydrogen emission at 2.122 μ m in the central region of S 201. These knots are clearly seen along the diffuse emission to the north–west and are probably obscured Herbig-Haro objects. High sensitivity and high resolution radio continuum images from GMRT observations at 610 and 1280 MHz show an arc-shaped structure due to the interaction between the HII region and the adjacent molecular cloud. The ionization front at the interface between the HII region and the molecular cloud is clearly seen comparing the radio, molecular hydrogen and Br γ images. The emission from the carriers of Unidentified Infrared Bands in the mid-infrared 6–9 μ m (possibly due to PAHs) as extracted from the Midcourse Space Experiment survey (at 8, 12, 14 and 21 μ m) is compared with the radio emission. The HIRES processed IRAS maps at 12, 25, 60 and 100 μ m have also been used for comparison. The spatial distribution of the temperature and the optical depth of the warm dust component around the S 201 region has been generated from the mid-infrared images.

A Chandra Observation of the Diffuse Emission Centered on the Low-Mass X-Ray Binary 4U 1755-33

We present an analysis of a Chandra observation of the field surrounding the low-mass X-ray binary 4U 1755-33, which has been in quiescence since 1996. In 2003, Angelini and White reported the appearance of a narrow 7 arcmin long jetlike feature centered on the position of 4U 1755-33 using the XMM-Newton telescope. Though the source and jet are not visibly apparent in our Chandra/ACIS-S image, there is a significant excess (4-6 sigma) of counts in a region that encloses the jet when compared to adjacent regions. We examined a knot of emission in the jet that was detected by XMM-Newton but not by Chandra and calculated that if the knot flux observed by XMM-Newton was concentrated in a point source, Chandra would have easily detected it; we therefore conclude that this knot of emission is diffuse. In summary, we suggest that the jetlike feature found previously in the XMM-Newton data is quite diffuse and likely a true jet, and is not due to a chance alignment of discrete point sources or point-like regions of emission associated with internal shocks.

SH 2-128, AN H II AND STAR FORMING REGION IN AN UNLIKELY PLACE

Near-infrared imaging photometry supplemented by optical spectroscopy and narrow-band imaging of the H II region Sh 2-128 and its environment are presented. This region contains a developed H II region and the neighboring compact H II region S 128N associated with a pair of water maser sources. Midway between these, the core of a CO cloud is located. The principal ionizing source of Sh 2-128 is an 07 star close to its center. A new spectroscopic distance of 9.4 kpc is derived, very similar to the kinematic distance to the nebula. This implies a galactocentric distance of 13.5 kpc and z = 550 pc. The region is optically thin with abundances close to those predicted by galactocentric gradients. The <TEX>$JHK_s$</TEX> images show that S 128N contains several infrared point sources and nebular emission knots with large near-infrared excesses. One of the three red Ks knots coincides with the compact H II region. A few of the infrared-excess objects are close to known mid- and far-infrared emission peaks. Star counts in J and <TEX>$K_s$</TEX> show the presence of a small cluster of B-type stars, mainly associated with S 128N. The <TEX>$JHK_s$</TEX> photometric properties together with the characteristics of the other objects in the vicinity suggest that Sh 2-128 and S 128N constitute a single complex formed from the same molecular cloud, with ages <TEX>${\~}10^6$</TEX> and < <TEX>$3 {\times} 10^5$</TEX> years respectively. No molecular hydrogen emission was detected at 2.12 <TEX>${\mu}m$</TEX>. The origin of this remote star forming region is an open problem.

AChandraX‐Ray Observation of A1991: The Late Stages of Infall?

We present results from a 38 ks Chandra X-ray observation of the z = 0.059 galaxy cluster A1991. The cluster has a bright X-ray core and a central temperature gradient that declines inward from 2.7 keV at 130 kpc to ≈1.6 keV at the cluster center. The radiative cooling time of the gas in the inner 10 kpc is about 0.5 Gyr, and it rises to 1 Gyr at a radius of 20 kpc. The cooling rate of the gas within the latter radius is 25 M☉ yr-1. The Chandra ACIS-S3 image shows that the intracluster medium has an asymmetric surface brightness distribution with respect to the central galaxy. Bright knots of soft X-ray emission embedded in a cometary structure are located approximately 10'' north of the optical center of the cD galaxy. Unlike the structures seen in other cooling flow clusters, the knots have no obvious association with the radio source. The structure's temperature of 0.83 keV makes it nearly 1 keV cooler than its surroundings, and its mass is 3.4 × 109 M☉. Based on its bow-shaped appearance and modest overpressure with respect to its surroundings, we interpret the structure as a cool mass concentration that is breaking apart as it travels northward through the center of the cluster.

ChandraObservation of the Central Region of the Cooling Flow Cluster A262: A Radio Source That Is a Shadow of Its Former Self?

We present a Chandra observation of the cooling flow cluster A262. Spectral fits show that the intracluster medium (ICM) in A262 cools by a factor of 3, from 2.7 to 0.9 keV, at the cluster center. A mass deposition rate of = 19 M☉ yr-1 is measured. Complex structure is found in the very inner regions of the cluster, including knots of emission and a clear deficit of emission to the east of the cluster center. The bright X-ray structures are located in the same regions as optical line emission, indicating that cooling to low temperatures has occurred in these regions. The X-ray deficit is spatially coincident with the eastern radio lobe associated with the active galactic nucleus hosted by the central cD galaxy. The region surrounding the X-ray hole is cool and shows no evidence that it has been strongly shocked. This joins the ranks of other cooling flow clusters with Chandra-detected bubbles blown by central radio sources. This source is different from the other well-known cases, in that the radio source is orders of magnitude less luminous and has produced a much smaller bubble. Comparing the energy output of the radio source with the luminosity of the cooling gas shows that energy transferred to the ICM from the radio source is insufficient to offset the cooling flow unless the radio source is currently experiencing a less powerful than average outburst and was more powerful in the past.

Near infrared observations of the star formation region GGD12-15

Near infrared imaging observations in JHK broad bands and HZ v=10 S(1) narrow band of the star formation region GGD12-15 are presented in this article. The images reveal young compact infrared clusters and infrared nebulae in association with infrared sources, as well as outflow activities characterized by H 2 emission knots. Most of the infrared point sources are invisible in the optical wave band. The JHK′ photometric results of 76 infrared point sources contain 32 with infrared excess, and 5 with the characteristics of protostars, indicating very active star formation activities in the molecular clouds. Massive stars (defined as those with spectral types earlier than B8) account for ∼ 10 – 26 per cent of all stars of the clusters. The K′ magnitude distribution of GGD12-15 peaks at 15.0 mag, and spreads broadly from 13.0 mag to 16.0 mag. The peak of the [H-K′l color distribution occurs at ∼0.7 mag, above which the redder components of the cluster make up 70 per cent of the total. The newly-discovered H2 emission knots are concentrated in the central area of the clusters, and the spatial distribution has obvious relation to violent star formation activities. Five of the emission knots are located in the central part of the molecular outflow, indicating that they may have been excited by the same source as the molecular outflow.

Properties of the exciting source of the outflow in iras 20231+3440 region

Presented are results of near-infrared JHK′ and H 2 imaging observations of the star forming region near IRAS 20231+3440, as well as results of K-band spectroscopic observation of the near-infrared point source IRS1 associated with the above. The JHK′ images indicate the presence of embedded young stellar objects. The narrow-band H2 image reveals a number of emission knots, some of which are aligned, suggestive of a molecular hydrogen jet. The northern part of the jet is associated with a known molecular flow, indicative of a physical connection. The orientation of the jet suggests that IRS1 may be its exciting source, the K-band spectrum of IRS1 providing further evidence. The energy spectrum of IRS1 derived from the near-infrared, MSX and IRAS data indicates that it is a medium-mass Class I young stellar object.

Discovery of [FeII]- and H$_\mathsf{2}$-emission from protostellar jets in the CB3 and CB230 globules

Four Bok globules were studied in the Near-Infrared, through narrow-band filters, centered at the 1.644 μm line of [Fell], the H 2 -line at 2.122 μm, and the adjacent continuum. We report the discovery of [Fell] and H 2 protostellar jets and knots in the globules CB3 and CB230. The [Fell]-jet in CB230 is defined by a continuous elongated emission feature, superimposed on which two knots are seen; the brighter one lies at the tip of the jet. The jet is oriented in the same direction as the large-scale CO outflow, and emerges from the nebulosity in which a Young Stellar Object is embedded. The H 2 emission associated with this jet is fainter and wider than the [FeII] emission, and is likely coming from the walls of the jet-channel. In CB3 four H 2 emission knots are found, all towards the blue-shifted lobe of the large-scale outflow. There is a good correspondence between the location of the knots and the blue-shifted SiO(5-4) emission, confirming that SiO emission is tracing the jet-like flow rather well. No line emission is found in the other two targets, CB188 and CB205, although in CB205 faint line emission may have been hidden in the diffuse nebulosity near the IRAS position. Around this position a small group of (≥10) stars is found, embedded in the nebula. A diffuse jet-like feature near this group, previously reported in the literature, has been resolved into individual stars.

The peculiar galaxy IC 1182: An ongoing merger?

High resolution broad and narrow band images and long slit spectroscopy of the peculiar galaxy IC 1182 are pre- sented. The analysis of the broad band images reveals a distorted morphology with a large, heavily obscured disk-like structure and several knots in the central region. Galactic material, some of it in the form of two slender tails, is detected well beyond the main body of the galaxy. The second, fainter tail and several knots are reported here for the first time. The galaxy has color indices of an early type object except U − B, which is significantly bluer than what is typical for this kind of galaxy. The narrow band images centered on different emission lines show that the galaxy is a very powerful emitter. Most of the knots detected in the central region and in the prominent tail emerging eastward from the galaxy are very luminous in Hα ,a nd have typical sizes about 1 kpc (FWHM). The emission in the main lines extends all over the galaxy, with plumes and arc-like structures seen in Hα at large distances from the center. The observed, uncorrected Hα flux corresponds to a total luminosity of 3.51 × 10 41 erg s −1 , about 3 times that of the starburst galaxy Arp 220. We have found that the internal extinction deduced from the observed Balmer decrement is high all along the slit, with EB−V ≈ 1, so the corrected SFR could amount to 90 Mper year. On this basis IC 1182 is found to be a very powerful starburst galaxy. Surprisingly, the source is not in the IRAS Point Source Catalogue. The emission knots detected in the central region of the galaxy have line ratios that place them close to the border of the region occupied by active nuclei in the diagnostic diagrams. Using the best determined diagnostic ratio, (O III)/Hβ vs. (N II)/Hα ,t hey can still be classified as extreme HII-like regions. We notice that the same kind of line ratios are also measured at different places in the galaxy, adding to the idea that the nuclear line ratios can be explained in terms of stellar photoionization. The metallicity we have measured for the ionized gas in the two brightest central knots is low, 0.1 Zand 0.06 Zrespectively, and their measured helium abundance is also lower than solar. In the main body of the galaxy, besides the reported knots, the distribution of the ionized gas resembles that of an inclined disk about 12 kpc in size. The spectroscopic data show however a complex rotation pattern. We interpret them as corresponding to two identifiable disk galaxies with observed rotation amplitudes of 200 km s −1 and 100 km s −1 respectively. The stellar absorption lines detected in the bigger system do not show any clear rotation pattern. The data presented here indicate that IC 1182 is a high luminosity starburst system. Its global properties and peculiarities can be understood as corresponding to two systems that can still be recognized, in the process of merging, with two tidal tails emerging from the central region of the galaxy. In the main tail there are several candidates forming tidal dwarf galaxies. The measured low metallicity of the ionized gas, together with the low amplitude of one of the systems, suggests that the process involves a late-type, gas-rich spiral galaxy that is supplying most of the gas to the system.