Apparent associations between bright galaxies and compact galaxies

Valtonen, M. J.; Teerikorpi, P.; Argue, A. N.

doi:10.1086/112179

Cited by 12 publications

(13 citation statements)

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“…The results have remained controversial since Valtonen, Teerikorpi & Argue (1978) found an excess of compact satellites with small angles relatives to the primary disc. Based on this work, Byrd & Valtonen (1987) argued that the anisotropy of Holmberg's sample was mainly due to selection effects, for he may have not considered these compact dwarf objects.…”

Section: Introductionmentioning

confidence: 99%

Anisotropy in the distribution of satellites around primary galaxies in the 2dF Galaxy Redshift Survey: the Holmberg effect

Sales

Lambas

2004

Monthly Notices of the Royal Astronomical Society

133

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We have analysed a sample of satellite and primary galaxies in the 2dF Galaxy Redshift Survey. In our study we find strong statistical evidence of the Holmberg effect (that is, a tendency for satellites to avoid regions along the line defined by the primary plane) within 500 kpc of the projected distance to the primary. This effect is present only when we restrict our analysis to objects with radial velocity relative to the primary |Δv| < 160 km s−1, which corresponds approximately to the mean of the distribution. We explore the dependence of this anisotropy on spectral type (η), colours and luminosities of both primaries and satellites, finding that objects with a low present‐day star formation rate present the most significant effect.

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Section: Introductionmentioning

confidence: 99%

Anisotropy in the distribution of satellites around primary galaxies in the 2dF Galaxy Redshift Survey: the Holmberg effect

Sales

Lambas

2004

Monthly Notices of the Royal Astronomical Society

133

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“…Dubinsky 1998). [The related ‘Holmberg effect’ (Holmberg 1969), the correlation of satellite positions with the minor axis of the primary (not in clusters), has also been studied fairly extensively observationally (Hawley & Peebles 1975; Valtonen, Teerikorpi & Argue 1978; MacGillivray et al 1982; Zaritsky et al 1997; Sales & Lambas 2004; Brainerd 2005) and with simulations (Navarro et al 2004; Azzaro et al 2005; Kang et al 2005; Libeskind et al 2005; Zentner et al 2005) and is another possible explanation, though unlike for clusters the results (magnitude and even sign of the effect) have been conflicting.] This effect may be used to explain the detection of non‐zero w g+ ( r p ) in L5 and L6: if some of these bright galaxies are BCGs of clusters, then we expect to find an overdensity of galaxies along their major axis, leading to positive w g+ .…”

Section: Intrinsic Alignments and Brightest Cluster Galaxiesmentioning

confidence: 99%

“…We do not detect II in any of these cases, so the actual power-law slope cannot be determined from the data.] Peebles 1975; Valtonen, Teerikorpi & Argue 1978;MacGillivray et al 1982;Zaritsky et al 1997;Sales & Lambas 2004;Brainerd 2005) Table 2. another possible explanation, though unlike for clusters the results (magnitude and even sign of the effect) have been conflicting.] This effect may be used to explain the detection of non-zero w g+ (r p ) in L5 and L6: if some of these bright galaxies are BCGs of clusters, then we expect to find an overdensity of galaxies along their major axis, leading to positive w g+ .…”

Section: N T R I N S I C a L I G N M E N T S A N D B R I G H T E S mentioning

confidence: 99%

Detection of large-scale intrinsic ellipticity--density correlation from the Sloan Digital Sky Survey and implications for weak lensing surveys

Mandelbaum

Hirata

Ishak

et al. 2006

Monthly Notices of the Royal Astronomical Society

267

427

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The power spectrum of weak lensing shear caused by large‐scale structure is an emerging tool for precision cosmology, in particular for measuring the effects of dark energy on the growth of structure at low redshift. One potential source of systematic error is intrinsic alignments of ellipticities of neighbouring galaxies [the intrinsic ellipticity—intrinsic ellipticity (II) correlation] that could mimic the correlations due to lensing. A related possibility pointed out by Hirata & Seljak is correlation between the intrinsic ellipticities of galaxies and the density field responsible for gravitational lensing shear [the gravitational shear—intrinsic ellipticity (GI) correlation]. We present constraints on both the II and GI correlations using 265 908 spectroscopic galaxies from the Sloan Digital Sky Survey (SDSS) and using galaxies as tracers of the mass in the case of the GI analysis. The availability of redshifts in the SDSS allows us to select galaxies at small radial separations, which both reduces noise in the intrinsic alignment measurement and suppresses galaxy–galaxy lensing (which otherwise swamps the GI correlation). While we find no detection of the II correlation, our results are none the less statistically consistent with recent detections found using the SuperCOSMOS survey. Extrapolation of these limits to cosmic shear surveys at z∼ 1 suggests that the II correlation is unlikely to have been a significant source of error for current measurements of σ8 with ∼ 10 per cent accuracy, but may still be an issue for future surveys with projected statistical errors below the 1 per cent level unless eliminated using photometric redshifts. In contrast, we have a clear detection of GI correlation in galaxies brighter than L* that persists to the largest scales probed (60 h−1 Mpc) and with a sign predicted by theoretical models. This correlation could cause the existing lensing surveys at z∼ 1 to underestimate the linear amplitude of fluctuations by as much as 20 per cent depending on the source sample used, while for surveys at z∼ 0.5 the underestimation may reach 30 per cent. The GI contamination is dominated by the brightest galaxies, possibly due to the alignment of brightest cluster galaxies (BCGs) with the cluster ellipticity due to anisotropic infall along filaments, although other sources of contamination cannot be excluded at this point. We propose that cosmic shear surveys should consider rejection of BCGs from their source catalogues as a test for GI contamination. Future high‐precision weak lensing surveys must develop methods to search for and remove this contamination if they are to achieve their promise.

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“…In addition, the 11 brightest satellites of the Milky Way form a flattened structure that is oriented roughly perpendicular to the disk (e.g., Lynden-Bell 1982;Majewski 1994). Conversely, Valtonen et al (1978) found a tendency for compact satellites to be aligned with the major axes of disk hosts. Hawley & Peebles (1975), Sharp et al (1979), andMacGillivray et al (1982), suggested that any anisotropy in the distribution of satellite galaxies was at most rather small, and perhaps non-existent.…”

Section: Introductionmentioning

confidence: 99%

Anisotropic Distribution of SDSS Satellite Galaxies: Planar (Not Polar) Alignment

Brainerd

2005

ApJ

156

201

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The distribution of satellite galaxies relative to isolated host galaxies in the Sloan Digital Sky Survey (SDSS) is investigated. Host-satellite systems are selected using three different methods, yielding samples of ∼ 3300, ∼ 1600, and ∼ 950 satellites. In the plane of the sky, the distributions of all three samples show highly significant deviations from circular symmetry (> 99.99%, > 99.99%, and 99.79% confidence levels, respectively), and the degree of anisotropy is a strong function of the projected radius, r p , at which the satellites are found. For r p ∼ < 100 kpc, the SDSS satellites are aligned preferentially with the major axes of the hosts. This is in stark contrast to the Holmberg effect, in which satellites are aligned with the minor axes of host galaxies. The degree of anisotropy in the distribution of the SDSS satellites decreases with r p and is consistent with an isotropic distribution at of order the 1-σ level for 250 kpc ∼ < r p ∼ < 500 kpc.

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Apparent associations between bright galaxies and compact galaxies

Cited by 12 publications

References 0 publications

Anisotropy in the distribution of satellites around primary galaxies in the 2dF Galaxy Redshift Survey: the Holmberg effect

Anisotropy in the distribution of satellites around primary galaxies in the 2dF Galaxy Redshift Survey: the Holmberg effect

Detection of large-scale intrinsic ellipticity--density correlation from the Sloan Digital Sky Survey and implications for weak lensing surveys

Anisotropic Distribution of SDSS Satellite Galaxies: Planar (Not Polar) Alignment

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