Clues on the origin of galactic angular momentum from looking at galaxy pairs

Cervantes-Sodi, B.; Hernández, X.; Park, Changbom

doi:10.1111/j.1365-2966.2009.16001.x

Cited by 33 publications

(46 citation statements)

References 70 publications

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“…Macciò et al (2007) did not find a correlation between λ and the environment in cosmological simulations, although other studies did find a correlation, using similar techniques (e.g. Avila‐Reese et al 2005; Cervantes‐Sodi et al 2008a,b, 2010, 2011). Avila‐Reese et al (2005) employed a ΛCDM N ‐body simulation to study the properties of galaxy‐sized dark matter haloes as a function of the global environment, where λ was one of the studied properties of the halo.…”

Section: Resultsmentioning

confidence: 77%

Density profile slopes of dwarf galaxies and their environment

Popolo

2011

Monthly Notices of the Royal Astronomical Society

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In this paper, we study how the dark matter density profiles of dwarf galaxies in the mass range 108–1010 M⊙ are modified by the interaction of the dwarf galaxy with neighbouring structures, and by the changing baryon fraction in dwarf galaxies. With this aim, and referring to an earlier paper by Del Popolo, we determine the density profiles of the dwarf galaxies, taking into account the effect of tidal interaction with neighbouring structures, the effects of ordered and random angular momentum, dynamical friction, the response of dark matter haloes to the condensation of baryons and the effects produced by the presence of baryons. As already shown in the earlier paper, the slope of the density profile of inner haloes flattens with decreasing halo mass, and the profile is well approximated by a Burkert profile. We thus treat the angular momentum generated by tidal torques and the baryon fraction as a parameter in order to understand how the latter influences the density profiles. The analysis shows that dwarf galaxies that have suffered a smaller tidal torque (and consequently have smaller angular momentum) are characterized by steeper profiles with respect to dwarf galaxies subject to higher torque. Similarly, dwarf galaxies that have a smaller baryon fraction also have steeper profiles than those that have a larger baryon fraction. When tidal torquing is shut down and baryons are not present, the density profile is very well approximated by an Einasto profile, similarly to dwarf galaxies obtained in dissipationless N‐body simulations. Then, we apply the result of the previous analysis to the dark matter halo rotation curves of three different dwarfs: NGC 2976, which is known to have a flat inner core; NGC 5949, which has a profile intermediate between a cored and a cuspy one; and NGC 5963, which has a cuspy profile. After calculating the baryon fraction, which is ≃0.1 for the three galaxies, we fitted the rotation curves, changing the value of the angular momentum. NGC 2976 has a higher value of ordered angular momentum (λ≃ 0.04) than NGC 5949 (λ≃ 0.025). For NGC 5963, a very steep profile can be obtained with a low value of λ (λ≃ 0.02) and also by decreasing the value of the random angular momentum. For NGC 2976, the tidal interaction with M81 could also have influenced the inner part of the density profile. Finally, we show how the inner density profile correlates with the tidal index for dwarf and low surface brightness galaxies given by Karachentsev et al.

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Section: Resultsmentioning

confidence: 77%

Density profile slopes of dwarf galaxies and their environment

Popolo

2011

Monthly Notices of the Royal Astronomical Society

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“…As mentioned before in the introduction, Park et al (2008) and Park & Choi (2009) have found that galaxy properties like morphology and luminosity depend on the distance to the nearest neighbour galaxy, even at fixed large‐scale density, specially when the galaxy is located within the virial radius of its nearest neighbour, with a major role played by the morphology of the neighbour. Regarding the spin parameter, in Cervantes‐Sodi, Hernandez & Park (2010), we showed that the angular momentum is also sensitive to galaxy–galaxy interactions, leading to a gradual decrease in the values of λ, as soon as the galaxies cross into their virial radii. This being so, the trends exhibited by our present sample could arise simply from ongoing galaxy–galaxy interactions, and not directly due to the interaction with the cluster itself, or could be a joint effect from the local density plus the neighbour environment, as proposed by PH09.…”

Section: Resultsmentioning

confidence: 86%

“…In Cervantes‐Sodi et al (2010), we showed that the perturbation on the spin parameter produced by the presence of a nearby companion is more tangible for d pair < 0.5 R vir . Choosing a value smaller than 0.5 R vir will allow us to explore inner regions with galaxies still not showing clear features of galaxy–galaxy interactions.…”

Section: Resultsmentioning

confidence: 95%

“…As a final test on the joint role played by galaxy–galaxy and galaxy–cluster interactions, we contrast the spin–clustercentric radius relation according to the morphology of the nearest neighbour. In Cervantes‐Sodi et al (2010), we noted that the response to galaxy–galaxy interactions depends on the morphology of the nearest neighbour, the case of an interaction with a late‐type galaxy showing much more significant disturbances in the spin value, probably due to the strong hydrodynamical effects of the interactions of two gaseous discs, specially in very close encounters, with d pair < 0.1 R vir . We plot the median λ d value as a function of d / r 200, cl for galaxies segregated according to the morphological type of their nearest neighbour (Fig.…”

Section: Resultsmentioning

confidence: 99%

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Quantifying galactic morphological transformations in the cluster environment

Cervantes-Sodi

Park

Hernández

et al. 2011

Monthly Notices of the Royal Astronomical Society

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We study the effects of the cluster environment on galactic morphology by defining a dimensionless angular momentum parameter, λd, to obtain a quantitative and objective measure of galaxy type. The use of this physical parameter allows us to take the study of morphological transformations in clusters beyond the measurements of merely qualitative parameters, e.g. spiral/elliptical (S/E) ratios, to a more physical footing. To this end, we employ an extensive Sloan Digital Sky Survey sample (Data Release 7) with galaxies associated with Abell galaxy clusters. The sample contains 121 relaxed Abell clusters and over 51 000 individual galaxies, which guarantees a thorough statistical coverage over a wide range of physical parameters. We find that the median λd value tends to decrease as we approach the cluster centre, with different dependences according to the mass of the galaxies and the hosting cluster; low‐ and intermediate‐mass galaxies show a strong dependence, while massive galaxies seem to show, at all radii, low λd values. By analysing trends in λd as functions of the nearest neighbour environment, clustercentric radius and velocity dispersion of clusters, we can identify clearly the leading physical processes at work. We find that in massive clusters (σ > 700 km s−1), the interaction with the cluster central region dominates, whilst in smaller clusters galaxy–galaxy interactions are chiefly responsible for driving galactic morphological transformations.

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“…There have been many observational studies 2 George James Conidis to look for alignment of baryonic spin with cosmic structure, but results have been contradictory. While some researchers have claimed to see alignment (Trujillo et al 2006;Lee & Erdogdu 2007;Paz et al 2008;Jones et al 2010), others have found that spin directions are random (Slosar & White 2009;Cervantes-Sodi et al 2010). In those studies which find evidence for alignment, there is a preference for a disk galaxy to have its spin vector directed along the midplane of its host sheet (Trujillo et al 2006;Varela et al 2012;Tempel & Libeskind 2013).…”

Section: Introduction and Overviewmentioning

confidence: 99%

Spin Alignment in Analogues of The Local Sheet

Conidis¹

2014

Proc. IAU

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Abstract.Tidal torque theory and simulations of large scale structure predict spin vectors of massive galaxies should be coplanar with sheets in the cosmic web. Recently demonstrated, the giants (Ks -22.5 mag) in the Local Volume beyond the Local Sheet have spin vectors directed close to the plane of the Local Supercluster, supporting the predictions of Tidal Torque Theory. However, the giants in the Local Sheet encircling the Local Group display a distinctly different arrangement, suggesting that the mass asymmetry of the Local Group or its progenitor torqued them from their primordial spin directions. To investigate the origin of the spin alignment of giants locally, analogues of the Local Sheet were identified in the SDSS DR9. Similar to the Local Sheet, analogues have an interacting pair of disk galaxies isolated from the remaining sheet members. Modified sheets in which there is no interacting pair of disk galaxies were identified as a control sample.Galaxies in face-on control sheets do not display axis ratios predominantly weighted toward low values, contrary to the expectation of tidal torque theory. For face-on and edge-on sheets, the distribution of axis ratios for galaxies in analogues is distinct from that in controls with a confidence of 97.6 % & 96.9%, respectively. This corroborates the hypothesis that an interacting pair can affect spin directions of neighbouring galaxies.

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Clues on the origin of galactic angular momentum from looking at galaxy pairs

Cited by 33 publications

References 70 publications

Density profile slopes of dwarf galaxies and their environment

Density profile slopes of dwarf galaxies and their environment

Quantifying galactic morphological transformations in the cluster environment

Spin Alignment in Analogues of The Local Sheet

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