NGC 5291: Implications for the Formation of Dwarf Galaxies

Malphrus, Benjamin K.; Simpson, Caroline E.; Gottesman, S. T.; Hawarden, T. G.

doi:10.1086/118574

Cited by 41 publications

(52 citation statements)

References 3 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…UGC 957, possibly a TDG linked to the NGC 520 merger (Arp 157), was not detected in CO. The compact tidal dwarf associated with (Duc & Mirabel 1998) with HI contours (Malphrus et al 1997) superimposed. First HI contour and contour spacing is 5 × 10 20 cm −2 ; the spatial resolution is 26 × 15 .…”

Section: Observations and Resultsmentioning

confidence: 99%

Abundant molecular gas in tidal dwarf galaxies: On-going galaxy formation

Braine

Duc

Lisenfeld

et al. 2001

A&A

149

227

View full text Add to dashboard Cite

Abstract. We investigate the process of galaxy formation as can be observed in the only currently forming galaxies -the so-called Tidal Dwarf Galaxies, hereafter TDGs -through observations of the molecular gas detected via its CO (Carbon Monoxide) emission. These objects are formed of material torn off of the outer parts of a spiral disk due to tidal forces in a collision between two massive galaxies. Molecular gas is a key element in the galaxy formation process, providing the link between a cloud of gas and a bona fide galaxy. We have detected CO in 8 TDGs (two of them have already been published in Braine et al. 2000, hereafter Paper I), with an overall detection rate of 80%, showing that molecular gas is abundant in TDGs, up to a few 10 8 M . The CO emission coincides both spatially and kinematically with the HI emission, indicating that the molecular gas forms from the atomic hydrogen where the HI column density is high. A possible trend of more evolved TDGs having greater molecular gas masses is observed, in accord with the transformation of HI into H2. Although TDGs share many of the properties of small irregulars, their CO luminosity is much greater (factor ∼100) than that of standard dwarf galaxies of comparable luminosity. This is most likely a consequence of the higher metallicity (&1/3 solar) of TDGs which makes CO a good tracer of molecular gas. This allows us to study star formation in environments ordinarily inaccessible due to the extreme difficulty of measuring the molecular gas mass. The star formation efficiency, measured by the CO luminosity per Hα flux, is the same in TDGs and full-sized spirals. CO is likely the best tracer of the dynamics of these objects because some fraction of the HI near the TDGs may be part of the tidal tail and not bound to the TDG. Although uncertainties are large for individual objects, as the geometry is unknown, our sample is now of eight detected objects and we find that the "dynamical" masses of TDGs, estimated from the CO line widths, seem not to be greater than the "visible" masses (HI + H2 + a stellar component). Although higher spatial resolution CO (and HI) observations would help reduce the uncertainties, we find that TDGs require no dark matter, which would make them the only galaxy-sized systems where this is the case. Dark matter in spirals should then be in a halo and not a rotating disk. Most dwarf galaxies are dark matter-rich, implying that they are not of tidal origin. We provide strong evidence that TDGs are self-gravitating entities, implying that we are witnessing the ensemble of processes in galaxy formation: concentration of large amounts of gas in a bound object, condensation of the gas, which is atomic at this point, to form molecular gas and the subsequent star formation from the dense molecular component.

show abstract

Section: Observations and Resultsmentioning

confidence: 99%

Abundant molecular gas in tidal dwarf galaxies: On-going galaxy formation

Braine

Duc

Lisenfeld

et al. 2001

A&A

149

227

View full text Add to dashboard Cite

show abstract

“…The large-scale HI structure of NGC 5291 is a ring (Malphrus et al 1997), inclined by about 45 degrees Fig. 9.…”

Section: Dark Matter In Tidal Dwarfs: the Case Of Ngc 5291mentioning

confidence: 99%

Kinematics of tidal tails in interacting galaxies: Tidal dwarf galaxies and projection effects

Bournaud

Duc²,

Amram

et al. 2004

A&A

104

120

View full text Add to dashboard Cite

Abstract. The kinematics of tidal tails in colliding galaxies has been studied via Fabry-Pérot observations of the Hα emission.With their large field of view and high spatial resolution, the Fabry-Pérot data allow us to probe simultaneously, in 2D, two kinematical features of the tidal ionized gas: large-scale velocity gradients due to streaming motions along the tails, and smallscale motions related to the internal dynamics of giant HII regions within the tails. In several interacting systems, massive (10 9 M ) condensations of HI, CO and stars are observed in the outer regions of tails. Whether they are genuine accumulations of matter or not is still debated. Indeed a part of the tidal tail may be aligned with the line-of-sight, and the associated projection effect may result in apparent accumulations of matter that does not exist in the 3D space. Using numerical simulations, we show that studying the large-scale kinematics of tails, it is possible to know whether these accumulations of matter are the result of projection effects or not. We conclude that several ones (Arp 105-South, Arp 242, NGC 7252, and NGC 5291-North) are genuine accumulations of matter. We also study the small-scale motions inside these regions: several small-scale velocity gradients are identified with projected values as large as 50-100 km s −1 accross the observed HII regions. In the case of NGC 5291-North, the spatial resolution of our observations is sufficient to detail the velocity field; we show that this system is rotating and self-gravitating, and discuss its dark matter content. The Fabry-Pérot observations have thus enabled us to prove that some 10 9 M condensations of matter are real structures, and are kinematically decoupled from the rest of the tail. Such massive and self-gravitating objects are the progenitors of the so-called "Tidal Dwarf Galaxies".

show abstract

“…It is surrounded by a giant H I ring with a diameter of ∼160 kpc and H I mass of ∼5 × 10 10 M (Malphrus et al 1997). A disturbed galaxy (the "Seashell") lies at a projected distance of ∼13 kpc (see Fig.…”

Section: The Collisional Galaxy Ngc 5291mentioning

confidence: 99%

Gas dynamics in tidal dwarf galaxies: Disc formation atz= 0

Lelli

Duc

Brinks

et al. 2015

A&A

124

View full text Add to dashboard Cite

Tidal dwarf galaxies (TDGs) are recycled objects that form within the collisional debris of interacting and merging galaxies. They are expected to be devoid of non-baryonic dark matter, since they can only form from dissipative material ejected from the discs of the progenitor galaxies. We investigate the gas dynamics in a sample of six bona fide TDGs around three interacting and post-interacting systems: NGC 4694, NGC 5291, and NGC 7252 ("Atoms for Peace"). For NGC 4694 and NGC 5291, we analyse existing H I data from the Very Large Array (VLA), while for NGC 7252 we present new H I observations from the Jansky VLA, together with long-slit and integral-field optical spectroscopy. For all six TDGs, the H I emission can be described by rotating disc models. These H I discs, however, have undergone less than a full rotation since the time of the interaction/merger event, raising the question of whether they are in dynamical equilibrium. Assuming that these discs are in equilibrium, the inferred dynamical masses are consistent with the observed baryonic masses, implying that TDGs are devoid of dark matter. This puts constraints on putative "dark discs" (either baryonic or non-baryonic) in the progenitor galaxies. Moreover, TDGs seem to systematically deviate from the baryonic Tully-Fisher relation. These results provide a challenging test for alternative theories like MOND.

show abstract

NGC 5291: Implications for the Formation of Dwarf Galaxies

Abstract: The possible formation and evolution of dwarf irregular galaxies from material derived from perturbed evolved galaxies is addressed via an H 1 study of a likely example, the peculiar system NGC 5291. This 1427 Astron.

Cited by 41 publications

References 3 publications

Abundant molecular gas in tidal dwarf galaxies: On-going galaxy formation

Abundant molecular gas in tidal dwarf galaxies: On-going galaxy formation

Kinematics of tidal tails in interacting galaxies: Tidal dwarf galaxies and projection effects

Gas dynamics in tidal dwarf galaxies: Disc formation atz= 0

Contact Info

Product

Resources

About