Aidan C. Crook

The 2MASS Redshift Survey?Description and Data Release

We present the results of the 2MASS Redshift Survey (2MRS), a ten-year project to map the full three-dimensional distribution of galaxies in the nearby universe. The Two Micron All Sky Survey (2MASS) was completed in 2003 and its final data products, including an extended source catalog (XSC), are available online. The 2MASS XSC contains nearly a million galaxies with K_s ≤ 13.5 mag and is essentially complete and mostly unaffected by interstellar extinction and stellar confusion down to a galactic latitude of |b| = 5° for bright galaxies. Near-infrared wavelengths are sensitive to the old stellar populations that dominate galaxy masses, making 2MASS an excellent starting point to study the distribution of matter in the nearby universe. We selected a sample of 44,599 2MASS galaxies with K_s ≤ 11.75 mag and |b| ≥ 5° (≥8° toward the Galactic bulge) as the input catalog for our survey. We obtained spectroscopic observations for 11,000 galaxies and used previously obtained velocities for the remainder of the sample to generate a redshift catalog that is 97.6% complete to well-defined limits and covers 91% of the sky. This provides an unprecedented census of galaxy (baryonic mass) concentrations within 300 Mpc. Earlier versions of our survey have been used in a number of publications that have studied the bulk motion of the Local Group, mapped the density and peculiar velocity fields out to 50 h^(–1) Mpc, detected galaxy groups, and estimated the values of several cosmological parameters. Additionally, we present morphological types for a nearly complete sub-sample of 20,860 galaxies with K_s ≤ 11.25 mag and |b| ≥ 10°.

Groups of galaxies in the two micron all sky redshift survey

We present the results of applying a percolation algorithm to the initial release of the Two Micron All Sky Survey Extended Source Catalog, using subsequently measured redshifts for almost all of the galaxies with K < 11.25 mag. This group catalog is based on the first near-IR all-sky flux-limited survey that is complete to |b| = 5°. We explore the dependence of the clustering on the length and velocity scales involved. The paper describes a group catalog, complete to a limiting redshift of 10^4 km s^(-1), created by maximizing the number of groups containing three or more members. A second catalog is also presented, created by requiring a minimum density contrast of δρ/ρ ≥ 80 to identify groups. We identify known nearby clusters in the catalogs and contrast the groups identified in the two catalogs. We examine and compare the properties of the determined groups and verify that the results are consistent with the UZC-SSRS2 and northern CfA redshift survey group catalogs. The all-sky nature of the catalog will allow the development of a flow-field model based on the density field inferred from the estimated cluster masses.

Detecting Good Abandonment in Mobile Search

Web search queries for which there are no clicks are referred to as abandoned queries and are usually considered as leading to user dissatisfaction. However, there are many cases where a user may not click on any search result page (SERP) but still be satisfied. This scenario is referred to as good abandonment and presents a challenge for most approaches measuring search satisfaction, which are usually based on clicks and dwell time. The problem is exacerbated further on mobile devices where search providers try to increase the likelihood of users being satisfied directly by the SERP. This paper proposes a solution to this problem using gesture interactions, such as reading times and touch actions, as signals for differentiating between good and bad abandonment. These signals go beyond clicks and characterize user behavior in cases where clicks are not needed to achieve satisfaction. We study different good abandonment scenarios and investigate the different elements on a SERP that may lead to good abandonment. We also present an analysis of the correlation between user gesture features and satisfaction. Finally, we use this analysis to build models to automatically identify good abandonment in mobile search achieving an accuracy of 75%, which is significantly better than considering query and session signals alone. Our findings have implications for the study and application of user satisfaction in search systems.

2MTF-II. New Parkes 21-cm observations of 303 southern galaxies

We present new 21-cm neutral hydrogen (H i) observations of spiral galaxies for the 2MASS Tully–Fisher (2MTF) survey. Using the 64-m Parkes radio telescope multibeam system we obtain 152 high signal-to-noise ratio H i spectra from which we extract 148 high-accuracy (<5 per cent error) velocity widths and derive reliable rotation velocities. The observed sample consists of 303 southern (δ < −40°) galaxies selected from the 2MASS Redshift Survey with Ks < 11.25 mag, cz < 10 000 km s−1 and axis ratio b/a < 0.5. The H i observations reported in this paper will be combined with new H i spectra from the Green Bank and Arecibo telescopes, together producing the most uniform Tully–Fisher survey ever constructed (in terms of sky coverage). In particular, due to its near-infrared selection, 2MTF will be significantly more complete at low Galactic latitude (|b| < 15°) and will provide a more reliable map of peculiar velocities in the local Universe.

Erratum: “Groups of Galaxies in the Two Micron All Sky Redshift Survey” (ApJ, 655, 790 [2007])

We present the results of applying a percolation algorithm to the initial release of the Two Micron All Sky Survey Extended Source Catalog, using subsequently measured redshifts for almost all of the galaxies with K < 11.25 mag. This group catalog is based on the first near-IR all-sky flux-limited survey that is complete to |b| = 5o. We explore the dependence of the clustering on the length and velocity scales involved. The paper describes a group catalog, complete to a limiting redshift of 104 km s-1, created by maximizing the number of groups containing three or more members. A second catalog is also presented, created by requiring a minimum density contrast of δρ/ρ ≥ 80 to identify groups. We identify known nearby clusters in the catalogs and contrast the groups identified in the two catalogs. We examine and compare the properties of the determined groups and verify that the results are consistent with the UZC-SSRS2 and northern CfA redshift survey group catalogs. The all-sky nature of the catalog will allow the development of a flow-field model based on the density field inferred from the estimated cluster masses.

2MTF III. H I 21 cm observations of 1194 spiral galaxies with the Green Bank Telescope

We present H i 21 cm observations of 1194 galaxies out to a redshift of 10 000 km s−1 selected as inclined spirals (i ≳ 60°) from the 2MASS redshift survey. These observations were carried out at the National Radio Astronomy Observatory Robert C. Byrd Green Bank Telescope (GBT). This observing programme is part of the 2MASS Tully–Fisher (2MTF) survey. This project will combine H i widths from these GBT observations with those from further dedicated observing at the Parkes Telescope, from the Arecibo Legacy Fast Arecibo L-band Feed Array survey at Arecibo, and S/N > 10 and spectral resolution vres < 10 km s−1 published widths from a variety of telescopes. We will use these H i widths along with 2MASS photometry to estimate Tully–Fisher distances to nearby spirals and investigate the peculiar velocity field of the local Universe. In this paper, we report on detections of neutral hydrogen in emission in 727 galaxies, and measure good signal to noise and symmetric H i global profiles suitable for use in the Tully–Fisher relation in 484.

Predicting User Satisfaction with Intelligent Assistants

There is a rapid growth in the use of voice-controlled intelligent personal assistants on mobile devices, such as Microsofts Cortana, Google Now, and Apples Siri. They significantly change the way users interact with search systems, not only because of the voice control use and touch gestures, but also due to the dialogue-style nature of the interactions and their ability to preserve context across different queries. Predicting success and failure of such search dialogues is a new problem, and an important one for evaluating and further improving intelligent assistants. While clicks in web search have been extensively used to infer user satisfaction, their significance in search dialogues is lower due to the partial replacement of clicks with voice control, direct and voice answers, and touch gestures. In this paper, we propose an automatic method to predict user satisfaction with intelligent assistants that exploits all the interaction signals, including voice commands and physical touch gestures on the device. First, we conduct an extensive user study to measure user satisfaction with intelligent assistants, and simultaneously record all user interactions. Second, we show that the dialogue style of interaction makes it necessary to evaluate the user experience at the overall task level as opposed to the query level. Third, we train a model to predict user satisfaction, and find that interaction signals that capture the user reading patterns have a high impact: when including all available interaction signals, we are able to improve the prediction accuracy of user satisfaction from 71% to 81% over a baseline that utilizes only click and query features.

Is This Your Final Answer?: Evaluating the Effect of Answers on Good Abandonment in Mobile Search

Answers on mobile search result pages have become a common way to attempt to satisfy users without them needing to click on search results. Many different types of answers exist, such as weather, flight and currency answers. Understanding the effect that these different answer types have on mobile user behavior and how they contribute to satisfaction is important for search engine evaluation. We study these two aspects by analyzing the logs of a commercial search engine and through a user study. Our results show that user click, abandonment and engagement behavior differs depending on the answer types present on a page. Furthermore, we find that satisfaction rates differ in the presence of different answer types with simple answer types, such as time zone answers, leading to more satisfaction than more complex answers, such as news answers. Our findings have implications for the study and application of user satisfaction for search systems.

Learning to Account for Good Abandonment in Search Success Metrics

Abandonment in web search has been widely used as a proxy to measure user satisfaction. Initially it was considered a signal of dissatisfaction, however with search engines moving towards providing answer-like results, a new category of abandonment was introduced and referred to as Good Abandonment. Predicting good abandonment is a hard problem and it was the subject of several previous studies. All those studies have focused, though, on predicting good abandonment in offline settings using manually labeled data. Thus, it remained a challenge how to have an online metric that accounts for good abandonment. In this work we describe how a search success metric can be augmented to account for good abandonment sessions using a machine learned metric that depends on users viewport information. We use real user traffic from millions of users to evaluate the proposed metric in an A/B experiment. We show that taking good abandonment into consideration has a significant effect on the overall performance of the online metric.

Reconstructing the peculiar velocity of the Local Group with modified gravity and 2MASS

The peculiar velocity of the Local Group (LG), reconstructed from inhomogeneities in the local density field, differs in direction and magnitude from the velocity inferred from the cosmic microwave background (CMB) dipole. We investigate whether generalized theories of gravity, which predict a modified growth of perturbations, are able to alleviate this discrepancy. We introduce a general formalism for calculating the real-space peculiar-velocity field for modified gravity and theories with interactions in the dark sector. For different classes of theories - scalar-tensor and higher dimensional gravity - we reconstruct the LG peculiar velocity using groups of galaxies identified in the 2MASS Redshift Survey. We show that, for realistic parameters, the change in direction, with respect to the standard general relativity result, is less than 2°; this is significantly smaller than the ∼40° angular discrepancy between the reconstructed LG velocity and the dipole in the CMB.