Deficit of luminous and normal red galaxies in cosmic voids

ABSTRACT We construct a sample of 10 680 wall galaxies and 3064 void galaxies with MR ≲ −20 by cross-referencing a void catalogue from literature with Baryon Oscillation Spectroscopic Survey (BOSS) CMASS and WiggleZ galaxies, where the CMASS survey targets redder galaxies and the WiggleZ survey targets bluer galaxies. Comparing the density profiles of the red and blue galaxies as a function of the void radius, we find that the number ratio of red-to-blue galaxies increases with distances from the void centres, suggesting a deficit of luminous and normal red galaxies in voids. We find a mean (g – r) magnitude colour of 1.298 and 1.210 for the wall and void galaxies, respectively, when considering the combined red and blue samples, which is found to be a significant difference. However, when considering the blue and red samples separately, we find no significant colour difference. We conclude that the constituents galaxies of each population, rather than intrinsic colour difference, is the main driver in the apparent average colour difference of galaxies in voids and walls, indicating a deficit of luminous and normal red galaxies in voids. Our analysis suggests that the primary environmental-dependence effect on galaxy evolution for normal and luminous galaxies between void and wall regions is manifested in the number of red galaxies, which depends on the environmental-dependent merger history. Using a semi-analytic simulation model, we can successfully reproduce the apparent colour difference between the void and wall galaxies.

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Probing Galaxy Evolution in Massive Clusters Using ACT and DES: Splashback as a Cosmic Clock

The Astrophysical Journal ◽

10.3847/1538-4357/ac0bbc ◽

2021 ◽

Vol 923 (1) ◽

pp. 37

Author(s):

Susmita Adhikari ◽

Tae-hyeon Shin ◽

Bhuvnesh Jain ◽

Matt Hilton ◽

Eric Baxter ◽

...

Keyword(s):

Galaxy Evolution ◽

Dark Matter Halos ◽

Density Profiles ◽

Atacama Cosmology Telescope ◽

Dark Energy Survey ◽

Radial Profiles ◽

Blue Galaxies ◽

Sunyaev Zel'dovich Effect ◽

Red Galaxies ◽

Massive Clusters

Abstract We measure the projected number density profiles of galaxies and the splashback feature in clusters selected by the Sunyaev–Zel’dovich effect from the Advanced Atacama Cosmology Telescope (AdvACT) survey using galaxies observed by the Dark Energy Survey (DES). The splashback radius is consistent with CDM-only simulations and is located at 2.4 − 0.4 + 0.3 Mpc h − 1 . We split the galaxies on color and find significant differences in their profile shapes. Red and green-valley galaxies show a splashback-like minimum in their slope profile consistent with theory, while the bluest galaxies show a weak feature at a smaller radius. We develop a mapping of galaxies to subhalos in simulations and assign colors based on infall time onto their hosts. We find that the shift in location of the steepest slope and different profile shapes can be mapped to the average time of infall of galaxies of different colors. The steepest slope traces a discontinuity in the phase space of dark matter halos. By relating spatial profiles to infall time, we can use splashback as a clock to understand galaxy quenching. We find that red galaxies have on average been in clusters over 3.2 Gyr, green galaxies about 2.2 Gyr, while blue galaxies have been accreted most recently and have not reached apocenter. Using the full radial profiles, we fit a simple quenching model and find that the onset of galaxy quenching occurs after a delay of about a gigayear and that galaxies quench rapidly thereafter with an exponential timescale of 0.6 Gyr.

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Assessment of bruise age on dark-skinned individuals using tristimulus colorimetry

Medicine Science and the Law ◽

10.1258/msl.2011.011038 ◽

2011 ◽

Vol 52 (1) ◽

pp. 6-11 ◽

Cited By ~ 9

Author(s):

D Thavarajah ◽

P Vanezis ◽

D Perrett

Keyword(s):

Objective Assessment ◽

B Value ◽

Forensic Analysis ◽

Control Area ◽

Sri Lankan ◽

Colour Difference ◽

Tristimulus Colorimetry ◽

South Indian ◽

Colour Measurements ◽

Significant Difference

Introduction Studies on the ageing of bruises have been reported on Caucasians or individuals of fair ethnicity. This study focuses on bruise changes in dark-skinned individuals using tristimulus colorimetry for forensic analysis in such individuals. Methods Eighteen subjects of South Indian or Sri-Lankan ethnicity were recruited. Subjects were bruised using a vacuum pump and then daily colour measurements were taken of the bruise using a tristimulus colorimeter. The L* a* b* readings were recorded of a control area and of the bruise until it disappeared. Two Caucasians were used for comparison. Results This study showed that, using colorimetry, bruises on dark-skinned individuals can be measured and analysed even if the bruises are unclear visually. As the bruise is beneath the skin, the colour difference Δ L*, Δ a* and Δ b* were calculated. All values showed a trend, indicating that the L* a* b* measuring technique is a reliable method to analyse bruises on dark-skinned individuals. Comparisons of Asian subjects and Caucasian subjects were performed. The largest difference was seen in the b* value. Statistical analysis showed that Δ L* colour difference was the most consistent (95% CI −4.05 to −2.49) showing a significant difference between days 1–4 and 5–8. Conclusion Objective assessment of bruises on dark-skinned individuals using the L* a* b* method of measuring gave reproducible results. Furthermore, the study showed that the yellowing of a bruise cannot be seen or measured with a tristimulus colorimeter on dark-skinned individuals due to the pigmentation of the skin. With further studies and more subjects, the age of bruises could potentially be assessed for use in forensic analysis.

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Senescence as the main driver of iodide release from a diverse range of marine phytoplankton

Biogeosciences ◽

10.5194/bg-17-2453-2020 ◽

2020 ◽

Vol 17 (9) ◽

pp. 2453-2471 ◽

Cited By ~ 1

Author(s):

Helmke Hepach ◽

Claire Hughes ◽

Karen Hogg ◽

Susannah Collings ◽

Rosie Chance

Keyword(s):

Sea Surface ◽

Marine Phytoplankton ◽

Phase Cell ◽

Diverse Range ◽

Biogeochemical Models ◽

Cell Mortality ◽

Significant Difference ◽

Main Driver ◽

Inorganic Iodine ◽

Iodine Release

Abstract. The reaction between ozone and iodide at the sea surface is now known to be an important part of atmospheric ozone cycling, causing ozone deposition and the release of ozone-depleting reactive iodine to the atmosphere. The importance of this reaction is reflected by its inclusion in chemical transport models (CTMs). Such models depend on accurate sea surface iodide fields, but measurements are spatially and temporally limited. Hence, the ability to predict current and future sea surface iodide fields, i.e. sea surface iodide concentration on a narrow global grid, requires the development of process-based models. These models require a thorough understanding of the key processes that control sea surface iodide. The aim of this study was to explore if there are common features of iodate-to-iodide reduction amongst diverse marine phytoplankton in order to develop models that focus on sea surface iodine and iodine release to the troposphere. In order to achieve this, rates and patterns of changes in inorganic iodine speciation were determined in 10 phytoplankton cultures grown at ambient iodate concentrations. Where possible these data were analysed alongside results from previous studies. Iodate loss and some iodide production were observed in all cultures studied, confirming that this is a widespread feature amongst marine phytoplankton. We found no significant difference in log-phase, cell-normalised iodide production rates between key phytoplankton groups (diatoms, prymnesiophytes including coccolithophores and phaeocystales), suggesting that a phytoplankton functional type (PFT) approach would not be appropriate for building an ocean iodine cycling model. Iodate loss was greater than iodide formation in the majority of the cultures studied, indicating the presence of an as-yet-unidentified “missing iodine” fraction. Iodide yield at the end of the experiment was significantly greater in cultures that had reached a later senescence stage. This suggests that models should incorporate a lag between peak phytoplankton biomass and maximum iodide production and that cell mortality terms in biogeochemical models could be used to parameterise iodide production.

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Observational Evidence for Spectral Evolution of Cluster Galaxies

Symposium - International Astronomical Union ◽

10.1017/s0074180900136198 ◽

1988 ◽

Vol 130 ◽

pp. 311-319

Author(s):

Alan Dressler ◽

James E. Gunn

Keyword(s):

Galaxy Evolution ◽

Representative Sample ◽

Observational Evidence ◽

Spectral Evolution ◽

Cluster Galaxies ◽

Luminous Galaxies ◽

Detector Technology ◽

Selection Of

The study of galaxy evolution with large lookback times is dominated by two difficult issues. The first is a technical matter. Even the most luminous galaxies are faint (mr < 19) at significant lookback times (z ≳ 0.5), and so spectrophotometric observations of average galaxies challenge our present telescope and detector technology. The second issue is the selection of objects in an unbiased way in order to assemble a representative sample of galaxies at the remote epoch. It is far too easy to chase only exotic objects whose very peculiarity has brought them to our attention. Though observations of such objects may be fascinating and revealing, they may tell us little about the evolution of an typical galaxy like our own.

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A method for classification of red, blue, and green galaxies using fuzzy set theory

Monthly Notices of the Royal Astronomical Society Letters ◽

10.1093/mnrasl/slaa152 ◽

2020 ◽

Vol 499 (1) ◽

pp. L31-L35

Author(s):

Biswajit Pandey

Keyword(s):

Fuzzy Sets ◽

Set Theory ◽

Fuzzy Set ◽

Fuzzy Set Theory ◽

Sloan Digital Sky Survey ◽

Sky Survey ◽

Blue Galaxies ◽

Boundary Sets ◽

Red Galaxies

ABSTRACT Red and blue galaxies are traditionally classified using some specific cuts in colour or other galaxy properties, which are supported by empirical arguments. The vagueness associated with such cuts are likely to introduce a significant contamination in these samples. Fuzzy sets are vague boundary sets that can efficiently capture the classification uncertainty in the absence of any precise boundary. We propose a method for classification of galaxies according to their colours using fuzzy set theory. We use data from the Sloan Digital Sky Survey (SDSS) to construct a fuzzy set for red galaxies with its members having different degrees of ‘redness’. We show that the fuzzy sets for the blue and green galaxies can be obtained from it using different fuzzy operations. We also explore the possibility of using fuzzy relation to study the relationship between different galaxy properties and discuss its strengths and limitations.

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<i>F</i>-region Pedersen conductivity deduced using the TIMED/GUVI limb retrievals

Annales Geophysicae ◽

10.5194/angeo-24-1311-2006 ◽

2006 ◽

Vol 24 (5) ◽

pp. 1311-1316 ◽

Cited By ~ 10

Author(s):

H. Kil ◽

M. DeMajistre ◽

L. J. Paxton ◽

Y. Zhang

Keyword(s):

Density Profiles ◽

Atlantic Sector ◽

F Region ◽

Equatorial Plasma Bubbles ◽

Significant Difference ◽

Instability Growth ◽

Rayleigh Taylor Instability ◽

Electron Density Profiles ◽

Apex Height ◽

Peak Value

Abstract. As a proxy of the Rayleigh-Taylor instability growth rate for equatorial plasma bubbles, we investigate the flux-tube integrated F-region Pedersen conductivity (ΣPF) using the electron density profiles (EDPs) provided by the Global Ultraviolet Imager (GUVI) on board the Thermosphere Ionosphere and Mesosphere Energetics and Dynamics (TIMED) satellite. The investigation is conducted using the EDPs obtained in the Atlantic sector at 19:00-22:00 LT during 4–17 August and 6-16 December 2002. The seasonal difference of the strength and location of the equatorial ionization anomalies (EIAs) induces a significant difference in the deduced ΣPF. Much stronger EIAs are created at higher altitudes and latitudes in December rather than in August. At 19:00–20:00 LT, the peak value of the ΣPF has 23 mhos at 1100 km apex height during 14–16 December and 18mhos at 600 km during 15–17 August. The ΣPF decreases as local time progresses. Therefore, ΣPF provides a preferred condition for the growth of bubbles to higher altitudes at 19:00-20:00 LT than at later hours, in December rather than in August in the Atlantic sector.

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The dependence of intrinsic alignment of galaxies on wavelength using KiDS and GAMA

Astronomy and Astrophysics ◽

10.1051/0004-6361/201834219 ◽

2019 ◽

Vol 622 ◽

pp. A90 ◽

Cited By ~ 5

Author(s):

Christos Georgiou ◽

Harry Johnston ◽

Henk Hoekstra ◽

Massimo Viola ◽

Konrad Kuijken ◽

...

Keyword(s):

Imaging Data ◽

Tidal Interactions ◽

Significant Difference ◽

Blue Galaxies ◽

Measurement Algorithm ◽

Alignment Model ◽

The Difference ◽

The Moment ◽

Linear Alignment ◽

Better Than

The outer regions of galaxies are more susceptible to the tidal interactions that lead to intrinsic alignments of galaxies. The resulting alignment signal may therefore depend on the passband if the colours of galaxies vary spatially. To quantify this, we measured the shapes of galaxies with spectroscopic redshifts from the GAMA survey using deep gri imaging data from the KiloDegree Survey. The performance of the moment-based shape measurement algorithm DEIMOS was assessed using dedicated image simulations, which showed that the ellipticities could be determined with an accuracy better than 1% in all bands. Additional tests for potential systematic errors did not reveal any issues. We measure a significant difference of the alignment signal between the g, r and i-band observations. This difference exceeds the amplitude of the linear alignment model on scales below 2 Mpc h−1. Separating the sample into central/satellite and red/blue galaxies, we find that the difference is dominated by red satellite galaxies.

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The Evolution of Galaxies in the Last 10 GYR

Symposium - International Astronomical Union ◽

10.1017/s0074180900048282 ◽

1994 ◽

Vol 161 ◽

pp. 649-651

Author(s):

K. Rakos ◽

J. Schombert ◽

T. Maindl ◽

N. Unger ◽

P. Obitsch

Keyword(s):

Galaxy Evolution ◽

Galaxy Formation ◽

Rest Frame ◽

Blue Colour ◽

Star Forming ◽

Blue Galaxies ◽

Single Burst ◽

The Mean ◽

The Difference ◽

Good Agreement

Rest-frame Strömgren colours are presented for a large number of galaxies in rich clusters between z = 0 and z = 1. Our observations confirm a strong, rest-frame, Butcher-Oemler effect where the fraction of blue galaxies increases from 20% at z < 0.4 to 80% at z = 0.9. After isolating the red objects in each cluster we have compared the mean colour of these old, non-star forming objects with SED models from the literature as a test for passive galaxy evolution in ellipticals. We find good agreement with single burst models which predict an epoch of galaxy formation from z = 2 to 5 (Rakos et al. 1988, 1991; Rakos & Schombert 1993). Although the results demonstrate a great deal of hope for modelling the fine details of colour evolution when our samples are extended into the near- and far-IR, there are reasons to believe that galaxies become, observationally, much more complicated beyond redshifts of 1. The rate of blue colour evolution between 0.6 and 0.9 suggests that by a redshift of 1.5 it will be impossible to tell the difference between galaxies which have completed a single burst at a formation redshift of 2 or ones which are undergoing constant star formation.

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Efficiency of coconut water immersion inhibiting browning incidence on cut-surface of fresh-cut ‘Gala’ apples during storage

MATEC Web of Conferences ◽

10.1051/matecconf/201819203004 ◽

2018 ◽

Vol 192 ◽

pp. 03004

Author(s):

Suriyan Supapvanich ◽

Dararat Anartnet ◽

Chutima Krungpree

Keyword(s):

Polyphenol Oxidase ◽

Water Immersion ◽

Coconut Water ◽

Total Phenols ◽

Colour Difference ◽

Browning Index ◽

Visual Appearance ◽

Significant Difference ◽

Fresh Cut ◽

Cut Surface

The purpose of the work was to investigate the efficiency of coconut water preventing browning incidence of fresh-cut product using ‘Gala’ apple as the fruit model. The fresh-cut apples were dipped in coconut water at the concentration of 0, 50 and 100% for 2 min and then kept at 4 ± 1 °C for 7 days. Browning-related parameters such as browning index (BI), browning score (BS), lightness (L*), whiteness index (WI), total colour difference (ΔE*), total phenols (TP), and polyphenol oxidase (PPO) activity were determined. The result showed that visual appearance of the fresh-cut apple was maintained by coconut water dip. Coconut water dip apparently lowered BI, BS and ΔE* increases and maintained L* and WI throughout the storage. The increases in TP and PPO activity of the fresh-cut apples were inhibited by coconut water dips. No significant difference in browning prevention efficiency of the both 50 and 100% coconut water dips was found. Thus 50% coconut water dip is an effectively natural alternative preventing browning incidence of fresh-cut products.

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A young galaxy cluster in the old Universe

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2182 ◽

2019 ◽

Vol 489 (2) ◽

pp. 2014-2029 ◽

Cited By ~ 1

Author(s):

Tetsuya Hashimoto ◽

Tomotsugu Goto ◽

Rieko Momose ◽

Chien-Chang Ho ◽

Ryu Makiya ◽

...

Keyword(s):

Dark Matter ◽

Galaxy Evolution ◽

Galaxy Formation ◽

Galaxy Cluster ◽

Dark Matter Halo ◽

Current Standard ◽

Local Universe ◽

Star Forming ◽

Blue Star ◽

Blue Galaxies

ABSTRACT Galaxies evolve from a blue star-forming phase into a red quiescent one by quenching their star formation activity. In high-density environments, this galaxy evolution proceeds earlier and more efficiently. Therefore, local galaxy clusters are dominated by well-evolved red elliptical galaxies. The fraction of blue galaxies in clusters monotonically declines with decreasing redshift, i.e. the Butcher–Oemler effect. In the local Universe, observed blue fractions of massive clusters are as small as ≲0.2. Here we report a discovery of a ‘blue cluster’ that is a local galaxy cluster with an unprecedentedly high fraction of blue star-forming galaxies yet hosted by a massive dark matter halo. The blue fraction is 0.57, which is 4.0σ higher than those of the other comparison clusters under the same selection and identification criteria. The velocity dispersion of the member galaxies is 510 km s−1, which corresponds to a dark matter halo mass of 2.0$^{+1.9}_{-1.0}\times 10^{14}$ M⊙. The blue fraction of the cluster is more than 4.7σ beyond the standard theoretical predictions including semi-analytic models of galaxy formation. The probability to find such a high blue fraction in an individual cluster is only 0.003 per cent, which challenges the current standard frameworks of the galaxy formation and evolution in the ΛCDM universe. The spatial distribution of galaxies around the blue cluster suggests that filamentary cold gas streams can exist in massive haloes even in the local Universe. However these cold streams have already disappeared in the theoretically simulated local universes.

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