arXiv subjects

Renee C. Kraan-Korteweg

Publications and source records attributed to Renee C. Kraan-Korteweg.

At least 19 recordsLinked to original sources

arXiv2026

Peculiar velocities at low Galactic latitude

The Laniakea Supercluster is the closest large scale structure of galaxies. Is such a structure expected in the standard cold dark matter model of cosmology? This would be a relatively simple question to answer, were it not for the fact that the Zone of Avoidance (ZOA) runs right through it. Recent improvements to this paucity of data in the innermost ZOA can be made from systematic 21 cm surveys using the MeerKAT telescope (e.g. Kraan-Korteweg et al. 2024), and implementing these HI-redshifts as an extension to the CosmicFlows4 database for reconstruction (Hollinger et al. 2026). In this paper we test the assumption that for the purpose of reconstruction, additional HI detected galaxies without peculiar velocity determinations could be placed at their Hubble distances. We present infrared photometry of 163 of these in HI detected MeerKAT ZOA galaxies, in addition to 2MASS Extended Sources in the ZOA to determine their peculiar velocities. Averaging these peculiar velocities into redshift bins, we find that peculiar velocity corrections in the Laniakea Supercluster ZoA region are not prohibitively large, and that one can proceed with its reconstruction using the copious redshift data now available.

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arXiv2025

Unveiling the largest structures in the nearby Universe: Discovery of the Quipu superstructure

For a precise determination of cosmological parameters we need to understand the effects of the local large-scale structure of the Universe on the measurements. They include modifications of the cosmic microwave background, distortions of sky images by large-scale gravitational lensing, and the influence of large-scale streaming motions on measurements of the Hubble constant. The streaming motions, for example, originate from mass concentrations with distances up to 250 Mpc. In this paper we provide the first all-sky assessment of the largest structures at distances between 130 and 250 Mpc and discuss their observational consequences, using X-ray galaxy clusters to map the matter density distribution. Among the five most prominent superstructures found, the largest has a length longer than 400 Mpc with an estimated mass of about 2 10e17 Msun. This entity, which we named Quipu, is the largest cosmic structure discovered to date. These superstructures contain about 45% of the galaxy clusters, 30% of the galaxies, 25% of the matter, and occupy a volume fraction of 13%, thus constituting a major part of the Universe. The galaxy density is enhanced in the environment of superstructures out to larger distances from the nearest member clusters compared to the outskirts of clusters in the field. We find superstructures with similar properties in simulations based on Lambda-CDM cosmology models. We show that the superstructures should produce a modification on the cosmic microwave background through the integrated Sachs-Wolf effect. Searching for this effect in the Planck data we found a signal of the expected strength, however, with low significance. Characterising these superstructures is also important for astrophysical research, for example the study of the environmental dependence of galaxy evolution as well as for precision tests of cosmological models.

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arXiv2018

A Zone of Avoidance catalogue of 2MASS bright galaxies. I. Sample description and analysis

We present a homogeneous 2MASS bright galaxy catalogue at low Galactic latitudes ($|b| \le 10.0^{\rm o}$, called Zone of Avoidance) which is complete to a Galactic extinction-corrected magnitude of $K^o_s \le 11.25^{\rm m}$. It also includes galaxies in regions of high foreground extinctions ($E(B-V) > 0.95^{\rm m}$) situated at higher latitudes. This catalogue forms the basis of studies of large-scale structures, flow fields and extinction across the ZoA and complements the ongoing 2MASS Redshift and Tully-Fisher surveys. It comprises 3763 galaxies, 70% of which have at least one radial velocity measurement in the literature. The catalogue is complete up to star density levels of $\log N_*/{\rm deg}^2 <4.5$ and at least for $A_K < 0.6^{\rm m}$ and likely as high as $A_K = 20^{\rm m}$. Thus the ZoA in terms of bright NIR galaxies covers only $2.5-4$% of the whole sky. We use a diameter-dependent extinction correction to compare our sample with an unobscured, high-latitude sample. While the correction to the $K_s$ -band magnitude is sufficient, the corrected diameters are too small by about $4''$ on average. The omission of applying such a diameter-dependent extinction correction may lead to a biased flow field even at intermediate extinction values as found in the 2MRS survey. A slight dependence of galaxy colour with stellar density indicates that unsubtracted foreground stars make galaxies appear bluer. Furthermore, far-infrared sources in the DIRBE/IRAS extinction maps that were not removed at low latitudes affect the foreground extinction corrections of three galaxies and may weakly affect a further estimated $\approx 20$% of our galaxies.

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arXiv2017

Predicting Structures in the Zone of Avoidance

The Zone of Avoidance (ZOA), whose emptiness is an artifact of our Galaxy dust, has been challenging observers as well as theorists for many years. Multiple attempts have been made on the observational side to map this region in order to better understand the local flows. On the theoretical side, however, this region is often simply statistically populated with structures but no real attempt has been made to confront theoretical and observed matter distributions. This paper takes a step forward using constrained realizations of the local Universe shown to be perfect substitutes of local Universe-like simulations for smoothed high density peak studies. Far from generating completely `random' structures in the ZOA, the reconstruction technique arranges matter according to the surrounding environment of this region. More precisely, the mean distributions of structures in a series of constrained and random realizations differ: while densities annihilate each other when averaging over 200 random realizations, structures persist when summing 200 constrained realizations. The probability distribution function of ZOA grid cells to be highly overdense is a Gaussian with a 15% mean in the random case, while that of the constrained case exhibits large tails. This implies that areas with the largest probabilities host most likely a structure. Comparisons between these predictions and observations, like those of the Puppis 3 cluster, show a remarkable agreement and allow us to assert the presence of the, recently highlighted by observations, Vela supercluster at about 180 Mpc/h, right behind the thickest dust layers of our Galaxy.

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arXiv2011

The SED of the nearby HI-massive LIRG HIZOA J0836-43: from the NIR to the radio domain

HIZOA J0836-43is one of the most HI-massive galaxies in the local (z<0.1) Universe. Not only are such galaxies extremely rare, but this "coelacanth" galaxy exhibits characteristics -- in particular its active, inside-out stellar disk-building -- that appear more typical of past (z ~ 1) star formation, when large gas fractions were more common. Unlike most local giant HI galaxies, it is actively star forming. Moreover, the strong infrared emission is not induced by a merger event or AGN, as is commonly found in other local LIRGs. The galaxy is suggestive of a scaled-up version of local spiral galaxies; its extended star formation activity likely being fueled by its large gas reservoir and, as such, can aid our understanding of star formation in systems expected to dominate at higher redshifts. The multi-wavelength imaging and spectroscopic observations that have led to these deductions will be presented. These include NIR (J H K) and MIR (Spitzer; 3-24micron) imaging and photometry, MIR spectroscopy, ATCA HI-interferometry and Mopra CO line emission observations. But no optical data, as the galaxy is heavily obscured due to its location in Vela behind the Milky Way.

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arXiv2011

Deep NIR Photometry of HI Galaxies Behind the Milky Way

Current studies of the peculiar velocity flow field in the Local Universe are limited by the lack of detection of galaxies behind the Milky Way. The contribution of the largely unknown mass distribution in this "Zone of Avoidance" (ZoA) to the dynamics of the Local group remains contraversial. We have undertaken a near infrared (NIR) survey of HI detected galaxies in the ZoA. The photomety derived here will be used in the NIR Tully-Fisher (TF) relation to derive the peculiar velocities of this sample of galaxies in the ZoA.

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arXiv2009

Properties of the extremely HI-massive galaxy HIZOA J0836-43

Little is known about the properties of extremely massive HI-galaxies. They are extremely scarce and are - according to hierarchical structure formation - only forming now (z < 1). The forthcoming deep HI SKA Pathfinders surveys will uncover many more of them. This will lead to a better understanding of their evolution and frequency, and the shape of the bright end of the HI mass function. The recently discovered galaxy HIZOA J0836-43 is one of the most HI-rich galaxies (M(HI)=7.5 x 10^10Msun - and the nearest of its kind. As such it is an ideal local probe of these elusive galaxies. Results from a detailed investigation in the near- (IRSF) and far-infrared (Spitzer) of this local HI-massive galaxy are presented. Unlike other giant HI galaxies, it is not of low surface brightness. The galaxy is found to be a luminous starbursting galaxy at an unexpected early stage of stellar mass building, more typical of star-forming galaxies at higher redshift (z~0.7). With regard to its environment, hence possible clues to its formation, the near infrared imaging survey finds HIZOAJ0836-43 to lie in a region underdense in L* galaxies - consistent with the observation that HI-massive galaxies are preferentially found in low density regions - in the presence, however, of an uncommonly large number of low stellar mass galaxies.

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arXiv2009

Parkes HI observations of galaxies behind the southern Milky Way. II. The Crux and Great Attractor regions (l ~ 289 degree to 338 degree)

As part of our programme to map the large-scale distribution of galaxies behind the southern Milky Way, we observed 314 optically-selected, partially-obscured galaxies in the Zone of Avoidance (ZOA) in the Crux and Great Attractor (GA) regions. The observations were conducted with the Parkes 64m radio telescope, in a single-pixel pointed mode, reaching an rms noise level of typically 2-6 mJy over the velocity search range of 400<v<10500km/s. A total of 162 galaxies were detected. This can be explained by the prominence of the GA overdensity in the survey regions, which leads to a relatively higher fraction of nearby galaxies. It is also evident from the quite narrow velocity distribution (largely confined to 3000-6000km/s) and deviates significantly from the expectation of a uniform galaxy distribution for the given sensitivity and velocity range. No systematic differences were found between detections and non-detections, in terms of latitude, foreground extinction, or environment, except for the very central part of the rich Norma cluster, where hardly any galaxies were detected. A detailed investigation of the HI content of the galaxies reveals strong HI deficiency at the core of the Norma cluster (within about a 0.4 Abell radius), similar to what has been found in the Coma cluster. The redshifts obtained by this observing technique result in a substantial reduction of the so-called redshift ZOA. This is obvious when analysing the large-scale structure of the new HI data in combination with data from optical ZOA redshift surveys. The lower latitude detections provide further evidence of the extension of the Norma Wall, across the ZOA, in particular its bending towards the Cen-Crux clusters above the Galactic plane at slightly higher redshift, rather than a straight continuation towards the Centaurus clusters.

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arXiv2007

Outlining the Local Void with the Parkes HI ZOA and Galactic Bulge Surveys

The Parkes deep HI ZOA survey has been extended between 2002 and 2004 towards higher latitudes in the Galactic Bulge region. This area of extreme star crowding and high extinction levels remains impenetrable at any other waveband regime. Preliminary results of the 3 dimensional distribution based on the combined HI-surveys are presented. We focus on the extent and "content" of the Local Void as outlined by these HI surveys, followed by a preliminary discussion of the properties of the few galaxies detected in the Local Void.

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arXiv2005

Cosmological Structures behind the Milky Way

This paper provides an update to the review on extragalactic large-scale structures uncovered in the Zone of Avoidance (ZOA) by Kraan-Korteweg & Lahav 2000, in particular in the Great Attractor region. Emphasis is given to the penetration of the ZOA with the in 2003 released NIR 2MASX Catalog. The distribution is little affected by the foreground dust. Galaxies can be identified to extinction levels of over A(B) < 10m except in the wider Galactic Bulge region (see Fig. 9) where star density is a strong delimiting factor. The shape of the NIR-ZOA is quite asymmetric due to Galactic features such as spiral arms and the Bulge, something that should not be ignored when using NIR samples for studies such as dipole determinations. Results are presented from the deep blind HI ZOA survey performed with the Multibeam Receiver at the Parkes telescope (v < 12700km/s). The distribution of the roughly one thousand discovered spiral galaxies in the optically and NIR impenetratable part of the ZOA clearly depict the prominence of the Norma Supercluster. With the optically identified galaxies in the ZOA, a picture emerges that bears a striking resemblance to the Coma cluster in the Great Wall: the rich Norma cluster (ACO 3627) lies within a great-wall like structure that can be traced at the redshift range of the cluster over 90dg on the sky, with two foreground filaments - reminiscent of the legs in the famous stick man - that merge in an overdensity at slightly lower redshifts around the radio galaxy PKS 1343-601 (see Figs. 14 & 16). (abridged)

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arXiv2004

The Zone of Avoidance: Optical Compared to Near-Infrared Searches

Galaxies uncovered in the Zone of Avoidance (ZOA) with deep optical searches are compared to the distribution of objects in the 2MASS Extended Source Catalog (2MASX). While the galaxy density of optical surveys is strongly correlated to the dust content, and become ineffective in uncovering the galaxy distribution at A_B > 3.0 mag, this effect is much less severe in the NIR. Galaxies can be identified in 2MASS at optical extinction layers of over 10mag. However, star density has been found to be the dominant limiting factor in the NIR in the wider Galactic Bulge region (see Fig. 4) where optical surveys still do quite well. Systematic positional offsets have also been found between objects in the 2MASX and the optical ZOA as well as other galaxy catalogs. These seem to have their origin in the astrometric reference frame used by these surveys as well as different fitting algorithms when determining positions (details are given in the Appendix). The astrometric offsets between 2MASX and more recent galaxy catalogs (or on the Digitized Sky Survey remeasured positions) are of the order of 1 - 1.5 arcsec, comparable to the relative dispersion in positions between these surveys. Still, it is advisable to take this effect into account when combining galaxies from different catalogs for observational purposes.

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arXiv2004

DENIS detections of highly obscured galaxies in the area around PKS1343-601

We present results of a search for galaxies around the highly obscured giant radio galaxy PKS1343-601 using the near-infrared DENIS survey. We compare our findings with surveys in the B-band, at the 21cm line emission, and with 2MASS. Recession velocities of galaxies in this area suggest a low-velocity-dispersion group or cluster of galaxies including an X-ray confirmed Seyfert 2. The colours of the galaxies have been used to examine the extinctions in this low-latitude area where IRAS/DIRBE estimates are unreliable. We find the true extinction to be roughly 15% lower than the IRAS/DIRBE extinctions.

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arXiv2004

The HI Parkes Deep Zone of Avoidance Survey

The 64-m Parkes telescope, equipped with the 21-cm multibeam receiver, has completed a sensitive survey (typically 6 mJy per beam rms) for HI galaxies in the Zone of Avoidance accessible to the telescope, 196 < l < 52 deg, and |b| < 5 deg. While the galaxy candidate inspection is not yet quite complete, and final number not yet determined, the survey has yielded about 1000 galaxies. The data, in the form of three-dimensional datacubes, have been inspected by eye, and candidate lists assembled, and about half have now been checked for reality, and accepted into the final catalog. The distributions on the sky and in redshift space are presented, showing galaxies belonging to previously-known structures, and newly-discovered features. Of the 469 confirmed HI galaxies, 191 have a NIR source within 6 arcmin in the 2MASS Extended Source Catalog, but the incidence of NIR counterparts is a strong function of longitude: in the low obscuration, low stellar surface density Puppis region, 131 of the 186 HI galaxies have 2MASS counterparts (70 percent), while in the Galactic bulge region, only 6 of the 155 HI detections have a 2MASS extended source coincident (4 percent). This is attributable to the HI survey's ability to detect galaxies even in regions of high foreground stellar surface density.

astro-ph↗

arXiv2004

A 2 x 2 Degree I-band Survey around PKS 1343-601

Motivated by the possibility that the highly obscured (A_B = 12 mag) radio galaxy PKS 1343-601 at (l,b,cz) = (309.7, +1.8, 3872km/s) might constitute the center of a heavily obscured cluster in the Great Attractor region, we have imaged about 2 x 2 degree of the core of this prospective cluster in the I-band using the WFI at the ESO 2.2m telescope at La Silla. We were able to identify 49 galaxies and 6 uncertain galaxy candidates. Although their distribution does not resemble a centrally condensed, massive cluster, its appearance -- severely influenced by the strong dust gradient across our surveyed region -- is entirely consistent with a cluster.

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arXiv2003

Extragalactic Large-Scale Structures behind the Southern Milky Way. IV. Redshifts Obtained with MEFOS

Abbreviated: As part of our efforts to unveil extragalactic large-scale structures behind the southern Milky Way, we here present redshifts for 764 galaxies in the Hydra/Antlia, Crux and Great Attractor region (266deg < l < 338deg, |b| < 10deg), obtained with the Meudon-ESO Fibre Object Spectrograph (MEFOS) at the 3.6-m telescope of ESO. The observations are part of a redshift survey of partially obscured galaxies recorded in the course of a deep optical galaxy search behind the southern Milky Way. A total of 947 galaxies have been observed, a small percentage of the spectra (N=109, 11.5%) were contaminated by foreground stars, and 74 galaxies (7.8%) were too faint to allow a reliable redshift determination. With MEFOS we obtained spectra down to the faintest galaxies of our optical galaxy survey, and hence probe large-scale structures out to larger distances (v <~ 30000 km/s) than our other redshift follow-ups. The most distinct large-scale structures revealed in the southern Zone of Avoidance are discussed in context to known structures adjacent to the Milky Way.

astro-ph↗

arXiv2002

Parkes HI observations of galaxies behind the southern Milky Way. - I. The Hydra/Antlia region (l : 266 to 296 deg)

As part of our program to map the large-scale distribution of galaxies behind the Milky Way, we used the Parkes 210 ft (64 m) radio telescope for pointed HI observations of a sample of low surface-brightness (due to heavy obscuration) spiral galaxies selected from the deep optical Zone of Avoidance (ZOA) galaxy catalog in the Hydra/Antlia region (Kraan-Korteweg 2000a). Searching a simultaneous velocity range of either 300 to 5500 km/s or 300 to 10500 km/s to an rms level of typically 2 - 4 mJy resulted in detections in 61 of the 139 pointings, leading to a total of 66 detections (an additional detection was made in a reference position, and two other pointings revealed two and four independent signals respectively). Except for 2 strong HI emitters identified in the shallow Zone of Avoidance HI survey (Henning et al. 2000), all HI detections are new. An analysis of the properties of the observed and detected galaxies prove that pointed HI observations of highly obscured galaxies allow the tracing of a population of nearby, intrinsically large and bright spiral galaxies that otherwise would not be recovered. The new data identified a previously unrecognized nearby group at l=287.5, b=-9.5, V=1700 km/s, the continuation of the Hydra/Antlia filament on the opposite side of the Galactic plane, and helped to delimit a distinct void in the ZOA centered at 2000 km/s.

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arXiv2001

A catalogue of galaxies behind the southern Milky Way. - II. The Crux and Great Attractor regions (l = 289deg - 338deg)

In this second paper of the catalogue series of galaxies behind the southern Milky Way, we report on the deep optical galaxy search in the Crux region (289deg <= l <= 318deg and -10deg <= b <= 10deg) and the Great Attractor region (316deg <= l <= 338deg and -10deg <= b <= 10deg). The galaxy catalogues are presented, a brief description of the galaxy search given, as well as a discussion on the distribution and characteristics of the uncovered galaxies. A total of 8182 galaxies with major diameters D >= 0.2 arcmin were identified in this ~850 square degree area: 3759 galaxies in the Crux region and 4423 galaxies in the Great Attractor region. Of the 8182 galaxies, 229 (2.8%) were catalogued before in the optical (3 in radio) and 251 galaxies have a reliable (159), or likely (92) cross-identification in the IRAS Point Source Catalogue (3.1%). A number of prominent overdensities and filaments of galaxies are identified. They are not correlated with the Galactic foreground extinction and hence indicative of extragalactic large-scale structures. Redshifts obtained at the South African Astronomical Observatory (SAAO) for 518 of the newly catalogued galaxies in the Crux and Great Attractor regions (Fairall et al. 1998; Woudt et al. 1999) confirm distinct voids and clusters in the area here surveyed. With this optical galaxy search, we have reduced the width of the optical `Zone of Avoidance' for galaxies with extinction-corrected diameters larger than 1.3 arcmin from extinction levels A_B >= 1.0 mag to A_B >= 3.0 mag: the remaining optical Zone of Avoidance is now limited by |b| <= 3deg (see Fig. 16).

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arXiv2000

An HI Survey of the Great Attractor Region

A blind HI survey using the Parkes telescope at |b|<5 deg, 300 deg < l < 332 deg has so far revealed 305 galaxies, most of which were previously unknown. These galaxies are used to map out the distribution of filaments and voids out to 10000 km/s. A preliminary measurement of the galaxy overdensity suggests only a moderate overdensity is present, and that the excess mass (above the background density) is ~2.10^{15}.Omega.M(sun). This is below the mass predicted in POTENT reconstructions of the local velocity field, and implies that the `Great Attractor' (GA) is not as massive as these reconstructions indicate, or does not lie hidden in the region investigated.

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