1,135 research outputs found
Men Also Like Shopping: Reducing Gender Bias Amplification using Corpus-level Constraints
Language is increasingly being used to define rich visual recognition
problems with supporting image collections sourced from the web. Structured
prediction models are used in these tasks to take advantage of correlations
between co-occurring labels and visual input but risk inadvertently encoding
social biases found in web corpora. In this work, we study data and models
associated with multilabel object classification and visual semantic role
labeling. We find that (a) datasets for these tasks contain significant gender
bias and (b) models trained on these datasets further amplify existing bias.
For example, the activity cooking is over 33% more likely to involve females
than males in a training set, and a trained model further amplifies the
disparity to 68% at test time. We propose to inject corpus-level constraints
for calibrating existing structured prediction models and design an algorithm
based on Lagrangian relaxation for collective inference. Our method results in
almost no performance loss for the underlying recognition task but decreases
the magnitude of bias amplification by 47.5% and 40.5% for multilabel
classification and visual semantic role labeling, respectively.Comment: 11 pages, published in EMNLP 201
The diverse evolutionary paths of simulated high-z massive, compact galaxies to z=0
Massive quiescent galaxies have much smaller physical sizes at high redshift
than today. The strong evolution of galaxy size may be caused by progenitor
bias, major and minor mergers, adiabatic expansion, and/or renewed star
formation, but it is difficult to test these theories observationally. Herein,
we select a sample of 35 massive, compact galaxies (
M, M/kpc) at in the
cosmological hydrodynamical simulation Illustris and trace them forward to
to uncover their evolution and identify their descendants. By , the
original factor of 3 difference in stellar mass spreads to a factor of 20. The
dark matter halo masses similarly spread from a factor of 5 to 40. The
galaxies' evolutionary paths are diverse: about half acquire an ex-situ
envelope and are the core of a more massive descendant, a third survive
undisturbed and gain very little mass, 15% are consumed in a merger with a more
massive galaxy, and a small remainder are thoroughly mixed by major mergers.
The galaxies grow in size as well as mass, and only 10% remain compact by
. The majority of the size growth is driven by the acquisition of ex-situ
mass. The most massive galaxies at are the most likely to have compact
progenitors, but this trend possesses significant dispersion which precludes a
direct linkage to compact galaxies at . The compact galaxies' merger rates
are influenced by their environments, so that isolated or satellite
compact galaxies (which are protected from mergers) are the most likely to
survive to the present day.Comment: 19 pages, 10 figures, MNRAS accepted version including 2 new figure
Galaxy interactions in IllustrisTNG-100, I: The power and limitations of visual identification
We present a sample of 446 galaxy pairs constructed using the cosmological simulation IllustrisTNG-100 at z = 0, with M_(FoF,dm)=10¹¹−10^(13.5) M⊙. We produce ideal mock SDSS g-band images of all pairs to test the reliability of visual classification schema employed to produce samples of interacting galaxies. We visually classify each image as interacting or not based on the presence of a close neighbour, the presence of stellar debris fields, disturbed discs, and/or tidal features. By inspecting the trajectories of the pairs, we determine that these indicators correctly identify interacting galaxies ∼45 per cent of the time. We subsequently split the sample into the visually identified interacting pairs (VIP; 38 pairs) and those which are interacting but are not visually identified (nonVIP; 47 pairs). We find that VIP have undergone a close passage nearly twice as recently as the non-VIP, and typically have higher stellar masses. Further, the VIP sit in dark matter haloes that are approximately 2.5 times as massive, in environments nearly 2 times as dense, and are almost a factor of 10 more affected by the tidal forces of their surroundings than the nonVIP. These factors conspire to increase the observability of tidal features and disturbed morphologies, making the VIP more likely to be identified. Thus, merger rate calculations which rely on stellar morphologies are likely to be significantly biased toward massive galaxy pairs which have recently undergone a close passage
Jellyfish galaxies with the IllustrisTNG simulations: I. Gas-stripping phenomena in the full cosmological context
We use IllustrisTNG, a suite of gravity and MHD simulations, to study the
demographics and properties of jellyfish galaxies in the full cosmological
context. By jellyfish galaxies, we mean satellites orbiting in massive groups
and clusters that exhibit highly asymmetric distributions of gas and gas tails.
We use the TNG100 run and select galaxies at redshifts with stellar
mass exceeding and with host halo masses of
. Among more than about 6000 (2600) galaxies
with stars (and some gas), we identify 800 jellyfish galaxies by visually
inspecting their gas and stellar mass maps in random projections. About
of cluster satellites are found with signatures of ram-pressure stripping and
gaseous tails stemming from the main luminous bodies. This is a lower limit,
since the random orientation entails a loss of about of galaxies that in
an optimal projection would otherwise be identified as jellyfish. The
connection with ram-pressure stripping is further confirmed by a series of
findings: jellyfish galaxies are more frequent at intermediate and large
cluster-centric distances (); they move through the
ICM with larger bulk velocities and Mach numbers than the general cluster
population, typically orbiting supersonically and experiencing larger ram
pressures. Furthermore, the gaseous tails usually extend in opposite directions
to the galaxy trajectory, with no relation between tail orientation and the
host's center. The frequency of jellyfish galaxies shows a very weak dependence
on redshift but larger fractions of disturbed gaseous
morphologies occur in more massive hosts and at smaller satellite masses.
Finally, jellyfish galaxies are late infallers ( Gyrs ago, at )
and the emergence of gaseous tails correlates well with the presence of bow
shocks in the ICM.Comment: 25 pages, 15 figures, Accepted for publication on MNRAS after minor
revision
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