Stellar Kinematics for the Central Spheroid in the Polar Disk Galaxy NGC 4650A

Iodice, E.; Arnaboldi, M.; Saglia, R. P.; Sparke, Linda S.; Gerhard, Ortwin; Gallagher, John S.; Combes, F.; Bournaud, F.; Capaccioli, M.; Freeman, K. C.

doi:10.1086/501520

Cited by 30 publications

(62 citation statements)

References 56 publications

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“…As suggested by the previous studies of PRGs (Spavone et al 2010;Iodice et al 2006), the critical physical parameters that can tell the differences between the three formation scenarios are 1) the total baryonic mass (stars plus gas) observed in the polar structure with respect to the central spheroid; 2) the kinematics along both the equatorial and meridian planes; 3) the metallicity and SFR in the polar structure.…”

Section: Formation History For Ugc 7576 and Ugc 9796: Discussion And mentioning

confidence: 94%

“…NGC 4650A is the prototype of the wide polar ring galaxies (PRGs), and it has been studied in detail to understand its formation and physical properties (Arnaboldi et al 1997;Gallagher et al 2002;Iodice et al 2002a;Swaters & Rubin 2003;Bournaud & Combes 2003;Iodice et al 2006) and to constrain many of the processes at work during galaxy interactions and merging. Very recently, Spavone et al (2010) have used deep longslit spectroscopy with FORS2@ESO-VLT to study the abundance ratios and metallicities of the HII regions associated to the polar disk in NGC 4650A and to test the cold accretion scenario for this object.…”

Section: Introductionmentioning

confidence: 99%

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Chemical abundances of the PRGs UGC 7576 and UGC 9796

Spavone

Iodice

Arnaboldi

et al. 2011

A&A

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Context. The study of both the chemical abundances of HII regions in polar ring galaxies and their implications for the evolutionary scenario of these systems has been a step forward both in tracing the formation history of the galaxy and giving hints toward the mechanisms at work during the building of a disk by cold accretion process. It is now important to establish whether such results are typical of the class of polar disk galaxies as a whole. Aims. The present work aims at checking the cold accretion of gas through a "cosmic filament" as a possible scenario for the formation of the polar structures in UGC 7576 and UGC 9796. If these form by cold accretion, we expect the HII regions abundances and metallicities to be lower than those of same-luminosity spiral disks, with values of Z ∼ 1/10 Z , as predicted by cosmological simulations. Methods. We used deep long-slit spectra, obtained with DOLORES@TNG in the optical wavelengths, of the brightest HII regions associated with the polar structures to derive their chemical abundances and star formation rate. We used the empirical methods, based on the intensities of easily observable lines, to derive the oxygen abundance 12+ log(O/H) of both galaxies. Such values are compared with those typical of different morphological galaxy types of comparable luminosity. Results. The average metallicity values for UGC 7576 and UGC 9796 are Z = 0.4 Z and Z = 0.1 Z , respectively. Both values are lower than those measured for ordinary spirals of similar luminosity, and UGC 7576 presents no metallicity gradient along the polar structure. These data, together with other observed features available for the two PRGs in previous works, are compared with the predictions of simulations of tidal accretion, cold accretion, and merging to disentangle these scenarios.

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Section: Formation History For Ugc 7576 and Ugc 9796: Discussion And mentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

Chemical abundances of the PRGs UGC 7576 and UGC 9796

Spavone

Iodice

Arnaboldi

et al. 2011

A&A

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“…The host galaxy is typically a spheroid, but there are cases where it is also a spiral disk (e.g., NGC 660; Karataeva et al 2004b). In some cases, the polar ring is very extended, two to three times the diameter of the central galaxy and it is rotating, in which case it is called a polar disk (e.g, NGC 4650A; Iodice et al 2006).…”

Section: Introductionmentioning

confidence: 99%

Compact stellar systems in the polar ring galaxies NGC 4650A and NGC 3808B: Clues to polar disk formation

Órdenes-Briceño

Georgiev

Puzia

et al. 2016

A&A

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Context. Polar ring galaxies (PRGs) are composed of two kinematically distinct and nearly orthogonal components, a host galaxy (HG) and a polar ring/disk (PR). The HG usually contains an older stellar population than the PR. The suggested formation channel of PRGs is still poorly constrained. Suggested options are merger, gas accretion, tidal interaction, or a combination of both. Aims. To constrain the formation scenario of PRGs, we study the compact stellar systems (CSSs) in two PRGs at different evolutionary stages: NGC 4650A with well-defined PR, and NGC 3808 B, which is in the process of PR formation. Methods. We use archival HST/WFPC2 imaging in the F450W, F555W, or F606W and F814W filters. Extensive completeness tests, PSF-fitting techniques, and color selection criteria are used to select cluster candidates. Photometric analysis of the CSSs was performed to determine their ages and masses using stellar population models at a fixed metallicity. Results. Both PRGs contain young CSSs (<1 Gyr) with masses of up to 5 × 10 6 M , mostly located in the PR and along the tidal debris. The most massive CSSs may be progenitors of metal-rich globular clusters or ultra compact dwarf (UCD) galaxies. We identify one such young UCD candidate, NGC 3808 B-8, and measure its size of r eff = 25.23−2.01 pc. We reconstruct the star formation history of the two PRGs and find strong peaks in the star formation rate (SFR, 200 M /yr) in NGC 3808 B, while NGC 4650 A shows milder (declining) star formation (S FR < 10 M /yr). This difference may support different evolutionary paths between these PRGs. Conclusions. The spatial distribution, masses, and peak star formation epoch of the clusters in NGC 3808 suggest for a tidally triggered star formation. Incompleteness at old ages prevents us from probing the SFR at earlier epochs of NGC 4650 A, where we observe the fading tail of CSS formation. This also impedes us from testing the formation scenarios of this PRG.

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“…Combes et al () and Bournaud & Combes () suggest that such cosmological infall is a viable alternative to tidal accretion for the NGC 4650A system (e.g. Iodice et al ; Spavone et al , ). Resonance .…”

Section: Introductionmentioning

confidence: 99%

The halo shape and evolution of polar disc galaxies

Snaith¹,

Gibson²,

Knebe

et al. 2012

Monthly Notices of the Royal Astronomical Society

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This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society © 2012 RAS © 2012 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.We examine the properties and evolution of a simulated polar disc galaxy. This galaxy is composed of two orthogonal discs, one of which contains old stars (old stellar disc) and the other both younger stars and cold gas (polar disc). By exploring the shape of the inner region of the dark matter halo, we are able to confirm that the halo shape is an oblate ellipsoid flattened in the direction of the polar disc. We also note that there is a twist in the shape profile, where the innermost 3kpc of the halo flattens in the direction perpendicular to the old disc and then aligns with the polar disc out until the virial radius. This result is then compared to the halo shape inferred from the circular velocities of the two discs. We also use the temporal information of the simulation to track the system's evolution and identify the processes which give rise to this unusual galaxy type. We confirm the proposal that the polar disc galaxy is the result of the last major merger, where the angular moment of the interaction is orthogonal to the angle of the infalling gas. This merger is followed by the resumption of coherent gas infall. We emphasize that the disc is rapidly restored after the major merger and that after this event the galaxy begins to tilt. A significant proportion of the infalling gas comes from filaments. This infalling gas from the filament gives the gas its angular momentum, and, in the case of the polar disc galaxy, the direction of the gas filament does not change before or after the last major mergerONS acknowledges the support of STFC through its PhD Studentship programme (PPA/S/S/2006/4526) and a fellowship from the European Commissions Framework Programme 7, through the Marie Curie Initial Training Network CosmoComp (PITN-GA-2009-238356).BKG, CBB, RJT and AK acknowledge the support of the UK’s Science & Technology Facilities Council (ST/F002432/1, ST/G003025/1).AK further acknowledges support by the SpanishMinisterio de Ciencia e Innovación (MICINN) in Spain through the Ramon y Cajal programme as well as the grants AYA 2009-13875-C03-02, AYA2009- 12792-C03-03, CSD2009-00064 and CAM S2009/ESP-1496. We thank the DEISA consortium, co-funded through EU FP6 project RI-031513 and the FP7 project RI-222919, for supportwithin theDEISA Extreme Computing Initiativ

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Stellar Kinematics for the Central Spheroid in the Polar Disk Galaxy NGC 4650A

Cited by 30 publications

References 56 publications

Chemical abundances of the PRGs UGC 7576 and UGC 9796

Chemical abundances of the PRGs UGC 7576 and UGC 9796

Compact stellar systems in the polar ring galaxies NGC 4650A and NGC 3808B: Clues to polar disk formation

The halo shape and evolution of polar disc galaxies

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