Atomic and molecular gas in the merger galaxy NGC 1316 (Fornax A) and its environment

Horellou, C.; Black, J. H.; Gorkom, Jacqueline van; Combes, F.; Hulst, J. M. van der; Charmandaris, V.

doi:10.1051/0004-6361:20011039

Cited by 63 publications

(113 citation statements)

References 56 publications

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“…The knowledge of radial velocities in this region so far stems from a few sources: Schweizer (1980) quoted ∆v rad −101 km/s as the offset to the systemic velocity of NGC 1316, which is in excellent agreement with the HI-velocity of SH2 from Horellou et al (2001) code. The velocity from emission lines for 431 is 1670 ± 20 km/s.…”

Section: Velocities and Velocity Mapsmentioning

confidence: 66%

“…Starting with the classical work of Schweizer (1980), it has been intensively studied at various wavelengths from X-rays to the radio regime (D'Onofrio et al 1995;Shaya et al 1996;Mackie & Fabbiano 1998;Arnaboldi et al 1998;Longhetti et al 1998;Kuntschner 2000;Horellou et al 2001;Goudfrooij et al 2001b,a;Gómez et al 2001;Kim & Fabbiano 2003;Bedregal et al 2006;Nowak et al 2008;Lanz et al 2010;Goudfrooij 2012).…”

Section: Introductionmentioning

confidence: 99%

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The globular cluster system of NGC 1316

Richtler

Hilker

Puzia

et al. 2017

A&A

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Context. The light of the merger remnant NGC 1316 (Fornax A) is dominated by old and intermediate-age stars. The only sign of current star formation in this big galaxy is the HII region SH2, an isolated star cluster complex with a ring-like morphology and an estimated age of 0.1 Gyr at a galactocentric distance of about 35 kpc. A nearby intermediate-age globular cluster, surrounded by weak line emission and a few more young star clusters, is kinematically associated. The origin of this complex is enigmatic. Aims. We want to investigate the nature of this star cluster complex. The nebular emission lines permit a metallicity determination which can discriminate between a dwarf galaxy or other possible precursors. Methods. We used the Integrated Field Unit (IFU) of the VIMOS instrument at the Very Large Telescope of the European Southern Observatory in high dispersion mode to study the morphology, kinematics, and metallicity employing line maps, velocity maps, and line diagnostics of a few characteristic spectra. Results. The line ratios of different spectra vary, indicating highly structured HII regions, but define a locus of uniform metallicity. The strong-line diagnostic diagrams and empirical calibrations point to a nearly solar or even super-solar oxygen abundance. The velocity dispersion of the gas is highest in the region offset from the bright clusters. Star formation may be active on a low level. There is evidence for a large-scale disk-like structure in the region of SH2, which would make the similar radial velocity of the nearby globular cluster easier to understand. Conclusions. The high metallicity does not fit to a dwarf galaxy as progenitor. We favour the scenario of a free-floating gaseous complex having its origin in the merger 2 Gyr ago. Over a long period the densities increased secularly until finally the threshold for star formation was reached. SH2 illustrates how massive star clusters can form outside starbursts and without a considerable field population.

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Section: Velocities and Velocity Mapsmentioning

confidence: 66%

Section: Introductionmentioning

confidence: 99%

The globular cluster system of NGC 1316

Richtler

Hilker

Puzia

et al. 2017

A&A

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“…Observations of atomic and molecular gas in NGC 1316 indicate that neutral atomic gas is absent while there is a significant amount of molecular gas (∼ M , ) mainly associated with the dust 8 5 # 10 patches along the minor axis (Horellou et al 2001); the spectrum in Figure 3 seems to exhibit H 2 rotational emission lines, S(2) 12.28 mm and S(3) 9.66 mm. The deep absorption feature at 4.33 mm (Fig.…”

Section: Resultsmentioning

confidence: 97%

Near- to Mid-Infrared Spectroscopy for the Giant Elliptical Galaxy NGC 1316 (Fornax A) with the AKARI Infrared Camera

Kaneda

Onaka

Sakon

2007

ApJ

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We present the near-to mid-infrared (∼2.5-13 mm) spectrum of the giant elliptical galaxy NGC 1316 (Fornax A) obtained with the Infrared Camera (IRC) on board AKARI. NGC 1316 is known to have a peculiar polycyclic aromatic hydrocarbon (PAH) emission spectrum with an unusually high ratio of the 11.3 mm to the 7.7 mm emission intensity through the Spitzer IRS observation. NGC 1316 is a 3 Gyr old merger remnant with a dormant nucleus that was rather active 0.1 Gyr ago; the relatively well-known evolutionary history makes the elliptical galaxy an ideal probe for studying long-term effects of past energetic events on the interstellar medium. We have found that there is no significant PAH emission feature at 3.3 mm while we have confirmed the peculiar PAH emission spectrum in the mid-infrared. We have detected a strong absorption feature at 4.3 mm, which may be attributed to solid-state CO 2 in grain mantles. We discuss physical implications for those unusual emission and absorption features.

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“…In the case of NGC 1317, star formation in the outer ring might have died out and the remaining HII-regions are only the debris of a previous prominent ring. Horellou et al (2001) note the unusually small HI-disk and mention the possibility that it has been affected by ram pressure, when transversing through the intergalactic hot medium. This then would have happened when the present intermediate-age population was young.…”

Section: A1 Ngc 1317mentioning

confidence: 97%

The globular cluster system of NGC 1316

Gómez¹,

Richtler²,

Infante³

et al. 2014

A&A

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Context. The merger remnant NGC 1316 (Fornax A) is one of the most important objects regarding the investigation of and thus an important object to study merger-related processes. A recent photometric study used globular clusters in NGC 1316 to constrain its star formation history, but without the knowledge of individual radial velocities. The kinematical properties of the globular cluster system in comparison with the diffuse stellar light might give more insight into the formation of NGC 1316. Of particular interest is the dark matter content. Planetary nebulae in NGC 1316 indicate a massive dark halo, and globular cluster velocities provide independent evidence. Aims. We aim at measuring radial velocities of globular clusters in NGC 1316. We use these kinematical data to investigate the global structure of NGC 1316 and to constrain the dark matter content. Methods. We perform multiobject spectroscopy with VLT/FORS2 and MXU. Out of 562 slits, we extract radial velocities for 177 globular clusters. Moreover, we measure radial velocities of the integrated galaxy light, using slits with a sufficiently bright sky. To these data, we add 20 cluster velocities from the literature. In an appendix, we identify new morphological features of NGC 1316 and its companion galaxy NGC 1317.Results. The GC sample based on radial velocities confirms the colour peaks already found in our photometric study. The bright clusters, which probably have their origin in a 2 Gyr old starburst and younger star formation events, avoid the systemic velocity. A Gaussian velocity distribution is found only for clusters fainter than about m R = 22 mag. The velocity distribution of clusters shows a pronounced peak at 1600 km s −1 . These clusters populate a wide area in the south-western region which we suspect to be a disk population. Globular clusters or subsamples of them do not show a clear rotation signal. This is different from the galaxy light, where rotation along the major axis is discernable out to 3 radius. The kinematic major axis of NGC 1316 is misaligned by about 10• with the photometric major axis, which might indicate a triaxial symmetry. A simple spherical model like that suggested by dynamical analyses of planetary nebulae also reproduces the velocity dispersions of the faint globular clusters. Conclusions. The central dark matter density of the present model resembles a giant elliptical galaxy. This contradicts population properties which indicate spiral galaxies as pre-merger components. Modified Newtonian dynamics (MOND) would provide a solution, but the kinematical complexity of NGC 1316 does not allow a really firm conclusion. However, NGC 1316 might anyway be a problem for a cold dark matter scenario, if the high dark matter density in the inner region is confirmed in future studies.

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Atomic and molecular gas in the merger galaxy NGC 1316 (Fornax A) and its environment

Cited by 63 publications

References 56 publications

The globular cluster system of NGC 1316

The globular cluster system of NGC 1316

Near- to Mid-Infrared Spectroscopy for the Giant Elliptical Galaxy NGC 1316 (Fornax A) with the AKARI Infrared Camera

The globular cluster system of NGC 1316

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