Measurement of intrinsic alignments in galaxy ellipticities

By M. Brown, A. Taylor, Nigel C. Hambly, S. Ifa, Edinburgh, I. College, London. 2000

188 citations recorded by the source corpus.

We measure the alignment of galaxy ellipticities in the local Universe over a range of scales using digitized photographic data from the {SuperCOSMOS} Sky Survey. We find for a magnitude cut of {bJ{\textless}20.5}, corresponding to a median galaxy redshift of z{\textasciitilde}0.1, and 2??106 galaxies, that the galaxy ellipticities exhibit a non-zero correlation over a range of scales between 1 and 100arcmin. We detect this correlation in two colours, {bJ} and R and, most significantly, in the cross-correlation between the two bands, which is less likely to be contaminated by systematics. In particular, we measure the variance of mean galaxy ellipticities, ??2(??), in square angular cells on the sky as a function of cell size and find that it lies in the range, 2??10- 4{\textgreater}=??2(??){\textgreater}{\textasciitilde}1??10-5 for cell side lengths of between 15{\textless}=??{\textless}=100arcmin. Considering the low median redshift of the galaxies in the sample and hence the relatively low effective cross-section for lensing of these galaxies by the large-scale structure of the Universe, we propose that we have detected an intrinsic alignment of galaxy ellipticities. We compare our results with recent analytical and numerical predictions made for intrinsic galaxy alignment and find good agreement. We discuss the importance of these results for measuring cosmic shear from upcoming shallow surveys (e.g. the Sloan Digital Sky Survey) and we outline how these measurements could possibly be used to constrain models of galaxy formation and/or measure the mass distribution in the local Universe.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/d6ca576c4adac65a4767a8292c5fc3a9034815a0

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Citations in the corpus

Gravitational lensing (2010, result): “Measurements of intrinsic alignments were found to agree well with these predictions [62, 270].”
Detection of large-scale intrinsic ellipticity—density correlation from the Sloan Digital Sky Survey and implications for weak lensing surveys (2005, methodology): “The original SuperCOSMOS intrinsic alignments analysis (Brown et al. 2002) used a median redshift of zmed = 0.1 for their sample with limiting magnitude bJ = 20.5, and this number was also used in the re-analysis by Heymans et al. (2004).”
CFHTLenS tomographic weak lensing cosmological parameter constraints: Mitigating the impact of intrinsic galaxy alignments (2013, methodology): “…studies (Catelan et al. 2001; Crittenden et al. 2001; Lee & Pen 2001), and the first low redshift observational constraints (Pen et al. 2000; Brown et al. 2002) resulted in a consistent picture; for deep weak lensing surveys, the contamination to the weak lensing signal was expected to be…”
Simultaneous measurement of cosmology and intrinsic alignments using joint cosmic shear and galaxy number density correlations (2009, background): “Intrinsic alignments have also been investigated observationally, where non-vanishing II and GI signals have been detected in several surveys (Brown et al. 2002; Heymans et al. 2004; Mandelbaum et al. 2006; Hirata et al. 2007; Brainerd et al. 2009).”
Analysis of two-point statistics of cosmic shear - I. Estimators and covariances (2002, background): “…the intrinsic orientation of the galaxies from which the shear is measured are correlated, e.g. due to tidal interactions of dark matter halos in which these galaxies are formed (Croft & Metzler 2000; Pen et al. 2000; Heavens et al. 2001; Catelan et al. 2001; Mackey et al. 2002; Brown et al. 2002).”
The Intrinsic Alignment of Galaxies and its Impact on Weak Gravitational Lensing in an Era of Precision Cosmology (2014, background): “The measurement by Brown et al. (2002) was later extended by Heymans et al. (2004).”
3D weak lensing (2003, background): “The most obvious of these is the redshift distribution of the sources - ignorance of the precise distribution is already a source of significant error in current surveys (see e.g. Brown et al. 2002b).”
Internal and External Alignment of the Shapes and Angular Momenta of ΛCDM Halos (2004, background): “…found that the spin directions of the 12,122 spiral galaxies in the Tully catalog are positively correlated at separations less than 3 h−1 Mpc, while Brown et al. (2002) have measured intrinsic correlations between galaxy orientations at a range of angular separations in the 2 × 106 galaxies of…”
The WiggleZ Dark Energy Survey: Direct constraints on blue galaxy intrinsic alignments at intermediate redshifts (2009, background): “Alternatively, it is possible to measure II correlations at low redshift without any redshift information, given that the cosmic shear signal below z ∼ 0.2 is vanishingly small (Brown et al. 2002).”
Spin alignments within the cosmic web: a theory of constrained tidal torques near filaments (2015, background): “…Metzler 2000; Schneider & Bridle 2010; Schneider et al. 2012; Joachimi et al. 2013b; Codis et al. 2015; Tenneti et al. 2015) and observational (e.g. Brown et al. 2002; Lee & Pen 2002; Bernstein & Norberg 2002; Heymans et al. 2004; Hirata et al. 2004; Hirata & Seljak 2004; Mandelbaum et al. 2006;…”
Potential sources of contamination to weak lensing measurements: constraints from N-body simulations (2006, unknown): “Investigated observationally (Brown et al. (2002); Lee etal.”
Constraints on intrinsic alignment contamination of weak lensing surveys using the MegaZ-LRG sample (2010, methodology): “The II signal can either be observed using galaxy ellipticity correlations at very low redshift where cosmic shear is negligible (Brown et al. 2002 in SuperCOSMOS) or by selecting galaxy pairs with small physical separation (Mandelbaum et al. 2006; Hirata et al. 2007; Okumura et al. 2009; Brainerd…”
The shear power spectrum from the COMBO-17 survey (2002, background): “Indeed, the few observational studies of intrinsic alignments carried out to date (Pen, Lee & Seljak 2000; Brown et al. 2002; Lee & Pen 2002) support arguments from both theoretical considerations (Crittenden et al. 2001; Catelan et al. 2001; Mackey et al. 2002) and numerical simulations (Heavens,…”
Galaxy Alignments: Observations and Impact on Cosmology (2015, methodology): “The first large scale study of intrinsic alignments in the cosmic shear era was Brown et al. (2002).”
The Galaxy-Mass Correlation Function Measured from Weak Lensing in the Sloan Digital Sky Survey (2003, background): “This effect has been seen in N-body simulations (Croft & Metzler 2000; Heavens, Refregier, & Heymans 2000), and there are possible detections in the Tully catalog (Pen, Lee, & Seljak 2000) and SuperCOSMOS Sky Survey data (Brown et al. 2002), although these data are not ideal for such a study.”
Galaxy Alignments: An Overview (2015, methodology): “The first statement regarding the orientations of galaxies that we have been able to trace was made by Fath (1914), who published a list of 1,031 galaxies observed with the 60-inch reflector at Mt. Wilson Solar Observatory. It contains position angles for approximately 60% of the objects and, while ”