Software Performance and Reliability Prediction

Brosch, Franz

doi:10.1007/978-1-4614-1614-2_10

Cited by 9 publications

(19 citation statements)

References 7 publications

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“…In this case the central condensation is a bar, not a 'bulge or elliptical' (Hoag 1950) and Gadotti & de Souza (2003) dubbed this object 'a barred galaxy without a disc'. The origin of Hoag-type objects is still a puzzle, but two different scenarios seem to be the most commonly accepted: (a) accretion of small satellites (Schweizer et al 1987), or (b) a strong bar instability (Brosch 1985), which destroys the disc and builds up a ring (e.g. Schwarz 1984;Byrd et al 1994a).…”

Section: A P P E N D I X a : N Ot E S O N I N D I V I D Ua L O B J E mentioning

confidence: 99%

Evolutionary paths to and from the red sequence: star formation and Hâi properties of transition galaxies atzâ¼ 0

Cortese

Hughes

2009

Monthly Notices of the Royal Astronomical Society

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We investigate the properties of galaxies between the blue and the red sequence (i.e. the transition region, 4.5 < NUV −H < 6 mag) by combining ultraviolet (UV) and near‐infrared imaging to 21‐cm H i line observations for a volume‐limited sample of nearby galaxies. We confirm the existence of a tight relation between colour and H i fraction across all the range of colours, although outside the blue cloud this trend becomes gradually weaker. Transition galaxies are divided into two different families, according to their atomic hydrogen content. ‘H i‐deficient’ galaxies are the majority of transition galaxies in our sample. They are found in high‐density environments and all their properties are consistent with a quenching of the star formation via gas stripping. However, while the migration from the blue cloud is relatively quick (i.e. ≲1 Gyr), a longer amount of time (a few Gyr at least) seems required to completely suppress the star formation and reach the red sequence. At all masses, migrating ‘H i‐deficient’ galaxies are mainly discs, implying that the mechanism responsible for today's migration in clusters cannot have played a significant role in the creation of the red sequence at high redshift. Conversely, ‘H i‐normal’ transition galaxies are a more heterogeneous population. A significant fraction of these objects show star formation in ring‐like structures and evidence for accretion/minor‐merging events suggesting that at least part of the H i reservoir has an external origin. The detailed evolution of such systems is still unclear, but our analysis suggests that, in at least two cases, galaxies might have migrated back from the red sequence after accretion events. Interestingly, the H i available may be sufficient to sustain star formation at the current rate for several billion years. Our study clearly shows the variety of evolutionary paths leading to the transition region and suggests that the transition galaxies may not be always associated with systems quickly migrating from the blue to the red sequence.

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Section: A P P E N D I X a : N Ot E S O N I N D I V I D Ua L O B J E mentioning

confidence: 99%

Evolutionary paths to and from the red sequence: star formation and Hâi properties of transition galaxies atzâ¼ 0

Cortese

Hughes

2009

Monthly Notices of the Royal Astronomical Society

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“…Another type of galaxy with rings is the 'accretion ring' (Buta & Combes 1996) of which Hoag's object is deemed to be the prototype. The literature describes arguments about its nature, whether this is a ring formed in a barred galaxy whose bar subsequently dissolved (Brosch 1985) or whether the core is not the remnant of a bar but an elliptical galaxy (Schweizer et al 1987) and the ring is the result of accretion. Schweizer et al described seven other galaxies as similar objects and defined a class of 'Hoag-type' objects that might be quite rare.…”

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confidence: 99%

On the nature of the apparent ring galaxy SDSS J075234.33+292049.8

Brosch

Kniazev

Моисеев

et al. 2010

Monthly Notices of the Royal Astronomical Society

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We show that an object classified as a galaxy in on‐line data bases and revealed on sky survey images as a distant ring galaxy is a rare case of polar ring galaxy (PRG) where the ring is only slightly inclined to the equatorial plane of the central body (CB). Imaging information from the Sloan Digital Sky Survey (SDSS) indicates that the diameter of the ring is about 36 kpc. The SDSS data was combined with long‐slit spectroscopic observations and with Fabry–Pérot interferometer Hβ mapping obtained at the Russian Academy of Sciences 6‐m telescope. We derived the complex morphologies of this presumed ring galaxy from a combination of SDSS images and from the kinematical behaviour of the CB and of the ring, and determined the stellar population compositions of the two components from the SDSS colours, from the spectroscopy and from models of evolutionary stellar synthesis. The metallicity of the ring material is slightly underabundant. The total luminosity and the total mass of the system are not extreme, but the rather high M/L ≃ 20 indicates the presence of large amounts of dark matter. We propose two alternative explanations of the appearance of this object. One is a ring formed by two semicircular and tight spiral arms at the end of a central bar. The apparent inclination between the ring and the CB, and a strange kink at the north‐east end of the ring, could be the result of a warp or of precession of the ring material. The object could, therefore, be explained as an extreme SBa(R) galaxy. The other possibility is that we observe a PRG where the inner object is an S0 and the ring is significantly more luminous than the central object. The compound object would then be similar to the NGC 4650A galaxy, but then it would be a rare object, with a polar component only modestly inclined to the equatorial plane of the CB. Arguments for (and against) both explanations are given and discussed, with the second alternative being more acceptable.

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“…UGC 4599 has the smallest recession velocity among all known Hoag‐type galaxies, including Hoag's Object itself, and is therefore potentially the best object for a detailed study of this unusual structure. The main properties of UGC 4599 are summarized in Table 1 along with those of Hoag's Object for comparison (see Brosch 1985 and Schweizer et al 1987).…”

Section: Introductionmentioning

confidence: 99%

“…However, most of these objects differ in some distinct way from Hoag's Object and none has a perfectly round core in its centre (Schweizer et al 1987;Wakamatsu 1990). E-mail: ido@wise.tau.ac.il (IF); noah@wise.tau.ac.il (NB) The mechanism that formed the ring in Hoag's Object was debated in the past (Brosch 1985;Schweizer et al 1987), and is not yet fully understood. An exhaustive discussion of galactic rings that includes a variety of ringed objects, also of Hoag-type galaxies, was presented by Buta & Combes (1996).…”

Section: Introductionmentioning

confidence: 99%

“…The hypothesis that the ring in Hoag's Object was formed in a disc at a time when a bar was present and later dissolved was first put forward by Brosch (1985). Indeed, most Hoag-type galaxies show elongated cores with discy features, and probably represent an evolved phase of barred early-type galaxies where the bar has almost completely dissolved (e.g.…”

Section: Introductionmentioning

confidence: 99%

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UGC 4599: a photometric study of the nearest Hoag-type ring galaxy

Finkelman

Brosch

2011

Monthly Notices of the Royal Astronomical Society

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We present a photometric study of UGC 4599, a low‐luminosity galaxy superficially resembling Hoag's Object in that on sky survey images it appears to be a complete ring surrounding a roundish core. The nature of the outer ring of Hoag‐type galaxies is still debated and may be related either to slow secular evolution or to environmental processes, such as galaxy–galaxy interactions. As the nearest of its kind, UGC 4599 is a perfect target for a detailed study of the peculiar structure of this type of objects. Surface photometry of the central body of the ring and the ring itself was performed using GALEX, Sloan Digital Sky Survey (SDSS) and Two Micron All Sky Survey (2MASS) photometric data available online. To identify bright clumps across the ring that could be H ii regions associated with the ring we obtained images of UGC 4599 at the Wise Observatory through U‐, B‐ and R‐band and narrow‐band rest‐frame Hα filters. Although classified in HyperLEDA as S0 with an external ring, we show that in UGC 4599 (a) the nearly round central body follows well an light profile almost all the way to the centre, (b) the isophotes are strongly twisted with a sharp 45° transition at a radius of r≃ 6 arcsec, (c) the blue ring seems to have reached near‐equilibrium configuration with the central body, (d) the ring is actually composed of a one‐and‐a‐half turn spiral feature and (e) one side of the spiral shows conspicuous star formation in the form of at least nine H ii regions, revealed by their Hα emission. Based on the photometric data, together with H i information from the literature, we characterize UGC 4599 as an elliptical‐like object surrounded by a luminous ring and a massive, extremely extended H i disc. Given its observed properties, we rule out UGC 4599 as representing a late phase in barred early‐type galaxies evolution. We discuss the origin of UGC 4599 and conclude that this galaxy could be the result of a major interaction between two gas‐rich spiral galaxies that took place at least 5 Gyr ago. However, deep optical imaging and a detailed stellar population analysis are required to determine whether the large gas reservoir could have been accreted directly from the intergalactic medium on to a pre‐existing elliptical galaxy in the early Universe. A detailed kinematical study will shed light on the exact nature of the central body and the ring of UGC 4599.

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Software Performance and Reliability Prediction

Cited by 9 publications

References 7 publications

Evolutionary paths to and from the red sequence: star formation and Hâi properties of transition galaxies atzâ¼ 0

Evolutionary paths to and from the red sequence: star formation and Hâi properties of transition galaxies atzâ¼ 0

On the nature of the apparent ring galaxy SDSS J075234.33+292049.8

UGC 4599: a photometric study of the nearest Hoag-type ring galaxy

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Software Performance and Reliability Prediction

Cited by 9 publications

References 7 publications

Evolutionary paths to and from the red sequence: star formation and Hâi properties of transition galaxies atzâ¼ 0

Evolutionary paths to and from the red sequence: star formation and Hâi properties of transition galaxies atzâ¼ 0

On the nature of the apparent ring galaxy SDSS J075234.33+292049.8

UGC 4599: a photometric study of the nearest Hoag-type ring galaxy

Contact Info

Product

Resources

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Evolutionary paths to and from the red sequence: star formation and Hâi properties of transition galaxies atzâ¼ 0

Evolutionary paths to and from the red sequence: star formation and Hâi properties of transition galaxies atzâ¼ 0