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UGC 5786 (NGC 3310, Arp 217). The unusual smooth outer plume on the western side of the galaxy is probably the result of a recent merger (Balick & Heckman 1981). The plume has a smaller radial velocity than the galaxy. Wehner & Gallagher (2005) evidenced a closed loop in the V and R band that may be tidal debris. Diffuse H{alpha} emission, not visible by James et al. (2004), is detected in our H{alpha} image all around the galaxy. A large portion of the star formation is located in a central ring surrounding an off-centred nucleus. The central region of the H{alpha} velocity field displays an S-shape pattern encircling two velocity peaks leading to two severe bumps in the rotation curve. The bright nucleus exhibits a steep velocity rise. Outside the nuclear region, the velocity decreases and then remains flat along the galaxy major-axis. Despite the evidence for perturbations, the rotation curve is fairly symmetric although showing some oscillations. Outflows are observed in the central region of the galaxy (~1 kpc) by Schwartz et al. (2006) where we measure large H{alpha} linewidths. The width of the H I profile at 20 per cent (330 km s^-1^ from Springob et al. 2005) is significantly larger than the amplitude of our H{alpha} velocity field, suggesting that we cannot reach the maximum rotation velocity with our H{alpha} data. Indeed, our H{alpha} rotation curve clearly reaches a maximum at about 120 km s^-1^ witH Its central bump at 0.5 kpc but the behaviour of the curve in the outer parts is too chaotic (with a total divergence between receding and approaching side beyond the optical limit) for concluding anything about the true maximum. The kinematical inclination has been determined by excluding the central spiral structure within the first kpc, leading to a rather higH Inclination of 53^deg^+/- 11^deg^. This is significantly higher than the morphological inclination of 16^deg^+/-25^deg^ (HyperLeda) but the difference remains compatible with the error bars. We finally choose the kinema tical inclination. 4.2.3 NGC 3310 - More than ten discrete X-ray sources, embedded in diffuse emission, can be seen in the ACIS image of this galaxy. One of the sources corresponds extremely well with the optical centre, and has been isolated for further study here. As this isolated source shows 1538 net counts, a high-quality spectrum can be extracted. Up to ~7 keV, the continuum is well defined, making a prominent emission feature clearly noticeable at 6.4 keV at a level of ~2{sigma} above the local continuum. The spectrum (Fig. 3) is well fitted with a power law, a thermal component and moderate intrinsic absorption. The power law is flatter than the canonical average for AGN. Fixing {GAMMA} at a canonical AGN value of 1.8 leads to a somewhat worse {chi}^2^, but the intrinsic column density remains virtually unchanged. The best fit (reduced {chi}^2^ = {chi}^2^_v_ ~0.8]) includes a gaussian component for an emission line fixed at ~6.4 keV with an equivalent width (EW) of 0.3 keV. A similar, if slightly poorer, fit is produced if the line energy and Gaussian {sigma} of the line profile are left free. In this case, the best fit energy is 6.4 +/- 0.1 keV. This cannot be achieved with a 6.7 keV line. Both the energy and Gaussian {sigma} must then be fixed, but this produces a poorer fit than without an emission line at all, and thus no F-test can be applied for such a line. Plotting data and fits shows clearly that only a narrow line at 6.4 keV is able to fit the sharp feature at >6 keV above the well defined continuum. Indeed, the calibrated F-test suggests that the fitted emission line is statistically significant: the F-statistic value for the observed spectrum is 4.8, with random probability 0.03. FC shows that more than 99% of the simulated spectra lead to a smaller F-value, and, correspondingly, higher random probabilities. NGC 3310. One of the four starburst galaxies of our sample, NGC 3310, is thought to have merged with a companion galaxy (Wehner & Gallagher 2005). It has been extensively studied in the UV and optical regions because of its peculiar properties. It is one of the bluest spiral galaxies in the de Vaucouleurs (1991) catalog and its far-infrared luminosity (L_ir_} = 1.1 x 10^10^ L_sun_) indicates that the starburst in this galaxy is comparable to that of the "prototypical" starburst galaxy M 82 (Smith et al. 1996). Our JHK spectrum of this object (see Fig. 3) displays a continuum that decreases in flux with wavelength. The emission line spectrum shows lines of only a few species, H I, He I, He II, [S II] [S III] and [Fe II], all spectroscopically unresolved. Molecular H2lines at K are barely detectable. The most prominent absorption features are the Ca II triplet and the CO bandheads in H and K. NGC 3310. Submillimetre emission is seen out to ~2/3 of the optical radius in most directions on the 850-{mu}m map. The peak of the submillimetre emission is offset by ~12 arcsec to the north-east from the centre of the optical core. This corresponds to a linear distance of 1.2 kpc at the assumed distance of NGC 3310. Good S/N and typical discordance. Clear rotation, patchy {sigma}_*_ field and a clear difference between central and extended {sigma}_*_. Possible high-velocity components in central LOSVD. Significant amounts of dust (Hughes et al. 2003). See Figures 14 and 15d. This nearly face-on Sbc spiral galaxy at a distance of 18.7 Mpc shows spiral arms with sporadic star-forming knots. ULX1 and ULX2 (IXO 38) are both around knots on spiral arms. NGC 3310.-In this sight line the H_2_ lines near O VI look very broad. Weaker J = 2 and J = 3 lines show that there is H_2_ absorption associated with both the low- and the intermediate-velocity gas in the sight line. The strongest H_2_ absorption is associated with the IV-Arch, and this is used to align the spectrum. Just using the Si II {lambda}1020.699 and Ar I {lambda}1048.220 lines would lead to an incorrect alignment. This is one of three sight lines where the thick disk O VI extends to more negative velocities than -120kms^-1^ (to -135 km s^-1^), but in which there is no obvious separate high-velocity component. This sight line passes through the Ursa Major window and HVCs complexes A and C lie just a few degrees away. The negative-velocity wing may be associated with O VI around the edges of these HVC complexes. The morphological classification as determined by us is indicated in parentheses next to the galaxy name, with our "chaotic circumnuclear dust" (C) category now not including those galaxies with obvious dust lanes (DL). Where the classification has already been made by Martini et al. (2003), we indicate this with "-mp." . 3.14. NGC 3310: An Inner Circumnuclear Ring? (C) Figure 7 (top). Spectra: The spectra are among the best in the sample, showing clear emission lines and obvious rotation. There is evidence for H II regions. Images: NGC 3310 is a well-known site of circumnuclear star formation and has been studied extensively by many authors (see Elmegreen et al. 2002 for a recent review). The STIS image shows an arc 0.5" (~40 pc) north of the galactic center. The color map shows this feature to be bluer than the surrounding medium, indicating that the arc may be part of an inner circumnuclear star formation ring. The R-H color map, shown in Figure 7, shows that there are significant amounts of dust present at the center of this galaxy, which would be consistent with a partially obscured ring. NGC 3310 (Fig. 44).-The spectrum of NGC 3310 is puzzling. This galaxy hosts a spectacular starburst, as seen in numerous H II regions. Yet the HUT spectrum does not show evidence for even a weak O star population. The absorption lines are narrow, and therefore can only be interstellar and/or from B stars with slow stellar winds. Even a weak O population (e.g., as predicted with a steep Miller-Scalo-type IMF) would produce observable, broad C IV. We can exclude continuous models of any age with any reasonable IMF slopes unless we truncate the upper IMF. Two model families are consistent with the observations: (i) continuous models with upper cutoff masses around 25M_sun_ and (ii) instantaneous models with standard IMF and ages between 7 and 15 Myr. The age limits are imposed by the absence of O stars and the relatively hard continuum below 1000{Angstrom}. The model in Figure 44 is for a continuous model of age 5Myr and an upper cutoff mass 25M_sun_. It fits the observations quite well but leaves open the question why we do not find a massive ionizing O star population over more than 2 kpc^2^. Our result is consistent with that from the morphological study by Conselice et al. (2000). The UV- and H- brightest regions in the center of NGC 3310 do not coincide. The HUT aperture apparently encompasses a region dominated by relatively evolved, nonionizing massive stars with little H{alpha} emission. NGC 3310 is one of the best examples of a local UV-bright starburst of moderately high luminosity whose unusual outer structure is probably the result of a recent merger with a smaller galaxy (Balick & Heckman 1981; Mulder & van Driel 1996). NGC 3310 is also extremely bright in far-infrared emission (e.g., Braine et al. 1993) and X-rays (Zezas, Georgantopoulos, & Ward 1998) and was one of the first known FUV-bright starbursts (Code & Welch 1982). In the optical NGC 3310 displays a striking "bow and arrow" appearance in its outer parts. This feature is one of the better studied morphological peculiarities in any starburst galaxy (Walker & Chincarini 1967; Balick & Heckman 1981; Bertola & Sharp 1984; Mulder, van Driel, & Braine 1995). It was once thought that this bow part was a spiral arm (Walker & Chincarini 1967), but it has been shown to be part of a shell or ripple pattern, possibly caused by the accretion of a low-mass companion galaxy (e.g., Balick & Heckman 1981; Schweizer & Seitzer 1988; Smith et al. 1996). NGC 3310 has an inner, symmetric spiral pattern and a significant amount of star formation tracing the spiral arms. A large portion of the star formation, based on H{alpha} images, is in a central ring surrounding an off-center nucleus (Fig. 2). Some star formation is occurring within the ring, but the nucleus is either dominated by an older population or is dusty (compare UV and R-band images in Fig. 2). The FOC UV image of NGC 3310 shows a similar morphology to the H{alpha} image; there is a ring of hot stars surrounding the central parts of the cluster. However, when comparing directly the UV, R, and H{alpha} morphologies, there are some obvious differences (Fig. 2). There is a double ring structure in the core of the galaxy, with the inner one composed of gas (H{alpha} emission) and the outer one composed of slightly older stars. The inner H{alpha} ring is immediately interior to the redder outer ring and is offset from the center of the galaxy. However, this outer ring is not dominated by H{alpha} emission as much as the arms leading away from the center are. Additionally there are stellar regions in the center that have little or no H{alpha} emission; likewise there are several regions near the western part of the center that are dominated by H{alpha} flux, with no continuum R light. In comparison of the H{alpha} and UV images of this galaxy (Fig.2), several regions at the upper left are found to be brighter in H{alpha} than in the UV. These are also areas with considerable H{alpha} flux but little UV flux in comparison to the other bright UV regions. There is an asymmetry in the difference, with the northwest region having less UV flux than the southwest region of the central ring around the galaxy. We conclude that this starburst is probably a result of star formation induced by a bar instability. The color map of this galaxy does not show large variations or the clumpy appearance of dust. Sbc(r)(merger) PH-7982-S Feb 1/2, 1981 103aO 12 min NGC 3310 is unusual because of the smooth outer plume that surrounds half the image. It is similar to plumes in NGC 7252 (panel 340), NGC 4038/4039 (panel 280), and others mentioned earlier in this section. Interpretation of these plumes and of the polar rings as merger events, by Toomre and Toomre (1972), Toomre (1977), Schweizer (1980, 1982, 1983, 1986), Quinn (1984), Schweizer, Whitmore, and Rubin (1983), Schweizer and Seitzer (1988), and others, may apply here as well. That the feature may be a merger rather than a tidal plume due to encounter is suggested by two circumstances. (1) NGC 3310 is isolated; there are no candidates in the nearby field for tidal companions. (2) Very short exposures on a plate taken with the Mount Wilson 60-inch reflector show two nuclei buried in the high-surface-brightness image, separated by 2". Each nucleus is sharp, and each is surrounded by galaxy material belonging separately to each. The chaotic nature of the spiral fragments, with their many knots and their high rate of current star formation, may have been induced by the event. The redshift of NGC 3310 is v_o = 1073 km/s. NGC 3310; SAB(r)bc, starburst. The central part of this bright peculiar galaxy has a complex morphology, with a ring of H II regions surrounding the nucleus (an H II region itself) at a radius of a few kiloparsecs, and with a "bow and arrow" structure in the northwest region (Walker & Chincarini 1967; Bertola & Sharp 1984). The galaxy has an extremely bright blue optical continuum (Telesco & Gatley 1984) and strong extended X-ray, UV, and radio emission of thermal origin (Fabbiano, Feigelson, & Zamorani 1982; van der Kruit & de Bruyn 1976). All these aspects, in addition to the intense optical emission lines (Heckman & Balick 1980) and the very high IR luminosity (L_IR_ ~ 3 X 10^10^ L_sun_; Telesco & Gatley 1984), place NGC 3310 among the most luminous star-forming galaxies. The most intense and youngest burst is taking place in the "jumbo" H II region, situated 15". southwest of the nucleus (Telesco & Gatley 1984). The IUE spectrum is in perfect agreement with the picture of a starbursting galaxy: the rising continuum and the deep absorption lines are typical of OB associations. NGC 3310 is an extreme starburst galaxy which stands out with a line ratio of 2.6 and very high L_FIR_ to M (H_2_) and FIR to blue ratios. It is discussed further in Paper II. Asymmetric spiral with many HII regions. Plate 1 Peculiar Distribution of Large H II Regions =MCG +09-18-008 = NGC 3310 = Arp 217; 11.0m, V_0_=+1075(RC1). Large H II regions concentrated on the opposite sides. First published and discussed by Vorontsov et al. (1964, 1966). Two large groups of big H II regions on opposite sides. At one side, there is a long arc transfixed by a jet which emerges from the location of the H II regions. Here this bow and arrow is underexposed. Rotation and mass studied by Bertola (1964), then by Walker and Chincarini (1967). They published an excellent series of photographs with exposures from 5s to 10m. M_ph_=-20.0. Another view of VV 356 is given on plate 7, labelled no. 406, where another peculiar feature is apparent. Plate 7 Ejection of the Twin Satellites MCG +09-18-008 = NGC 3310 = Arp 217; 11m, V_0_=+1090 (RC1). On plate 1 it is = VV 356 - another appearance. Twin blue galaxies ejected or gemmated. = Arp 217 Description: P.A.S.P., 79, 152, 1977. Photograph: Ap. J., 147, 416, 1967. Cont. Asiago, No. 172, 1965. Photometry: Ap. J., 147, 316, 1967. Astrofizika, 3, 529, 1967. Spectrum: Cont. Asiago, No. 172, 1965. Rotation Curve and Mass Determination: Cont. Asiago, No. 172, 1965. Ap. J., 147, 416, 1967. Astr. Ap., 8, 364, 1970. SN1974: IAU Circ. No. 2641, 1974. HI 21cm: A.J., 79, 767, 1974. Radio Observations: A.J., 78, 18, 1972. Astr. Ap., 15, 110, 1971. 31, 447, 1974. Arp 217 SAB(r)bc pec (de Vaucouleurs), Sb+ (Holmberg) Bright main body 1.8 x 1.7 Very faint outer disk See Perek and Kohoutek, Catalogue of Galactic Planetary Nebulae, Prague 1967, page 10 "Much H-alpha emission includes half arc outside galaxy" (Arp) Very bright, very small nucleus. Weak bar in a very bright (r): 0.35 arcmin x 0.25 arcmin. Several filamentary knotty arms. Asymmetric outer arm and filamentary extensions. Maximum extent: 6.9 arcmin x 3.6 arcmin (no obvious interacting component nearby); see also Ap. J., 51, 289, 1920. Heidelberg Veroff. Vol. 9, 1926 and Lund 9 dimensions are for the lens only. Spectrum: Lick Obs. Bull., 497, 1939. HMS Note No. 093 Early-type continuum with strong {lambda} 3727, and H{gamma} and H{beta} in emission. |