scholarly journals HST Observations Reveal the Curious Geometry of Circumgalactic Gas

2016 ◽  
Vol 11 (S321) ◽  
pp. 342-344
Author(s):  
Glenn G. Kacprzak ◽  
Sowgat Muzahid ◽  
Christopher W. Churchill ◽  
Nikole M. Nielsen ◽  
Jane C. Charlton
Keyword(s):  
Major Axis ◽  
Uv Spectra ◽  
Minor Axis ◽  
Strong Absorption ◽  
Current View ◽  
Gas Flows ◽  
Star Forming ◽  
Isolated Galaxies

AbstractWe have discovered that warm gas flows along galaxy major and minor axes detected out to 200 kpc. Our results are derived from a sample of HST-imaged isolated galaxies with nearby background quasars used to probe their 105K CGM detected in HST/COS UV spectra (traced by Ovi absorption). We constrain the geometry of the gas to reside between 20-40 degrees of the projected major axis and within 60 degrees of the projected minor axis, with little-to-no gas found in between. Furthermore, strong absorption systems tend to be found along the minor axes of star-forming galaxies. All of our results are consistent with the current view of the CGM originating from major axis-fed inflows/recycled gas and from minor axis-driven outflows.

scholarly journals A Comparison of Circumgalactic Mg ii Absorption between the TNG50 Simulation and the MEGAFLOW Survey

2021 ◽  
Vol 923 (1) ◽  
pp. 56
Author(s):  
Daniel DeFelippis ◽  
Nicolas F. Bouché ◽  
Shy Genel ◽  
Greg L. Bryan ◽  
Dylan Nelson ◽  
...  
Keyword(s):  
Angular Momentum ◽  
High Resolution ◽  
Gas Flow ◽  
Major Axis ◽  
Absorption Lines ◽  
Gas Flows ◽  
Lower Mass ◽  
Star Forming ◽  
Good Tracer ◽  
Normalization Factors

Abstract The circumgalactic medium (CGM) contains information on gas flows around galaxies, such as accretion and supernova-driven winds, which are difficult to constrain from observations alone. Here, we use the high-resolution TNG50 cosmological magnetohydrodynamical simulation to study the properties and kinematics of the CGM around star-forming galaxies in 1011.5–1012 M ⊙ halos at z ≃ 1 using mock Mg ii absorption lines, which we generate by postprocessing halos to account for photoionization in the presence of a UV background. We find that the Mg ii gas is a very good tracer of the cold CGM, which is accreting inward at inflow velocities of up to 50 km s−1. For sight lines aligned with the galaxy’s major axis, we find that Mg ii absorption lines are kinematically shifted due to the cold CGM’s significant corotation at speeds up to 50% of the virial velocity for impact parameters up to 60 kpc. We compare mock Mg ii spectra to observations from the MusE GAs FLow and Wind (MEGAFLOW) survey of strong Mg ii absorbers (EW2796 Å 0 > 0.5 Å). After matching the equivalent-width (EW) selection, we find that the mock Mg ii spectra reflect the diversity of observed kinematics and EWs from MEGAFLOW, even though the sight lines probe a very small fraction of the CGM. Mg ii absorption in higher-mass halos is stronger and broader than in lower-mass halos but has qualitatively similar kinematics. The median-specific angular momentum of the Mg ii CGM gas in TNG50 is very similar to that of the entire CGM and only differs from non-CGM components of the halo by normalization factors of ≲1 dex.

Design of Turning Area for LNG Terminal Base on Computer Simulation

2012 ◽  
Vol 215-216 ◽  
pp. 1236-1240
Author(s):  
Yao Tian Fan
Keyword(s):  
Computer Simulation ◽  
Theoretical Calculation ◽  
Cost Effective ◽  
Major Axis ◽  
Minor Axis ◽  
Computer Simulator

Design of turning area for sea port is generally done according to the outcome of theoretical calculation or real-ship trial. However, these methods only take into account some limited respects for planning a port or are not so cost-effective. In this paper, computer simulator is used for optimizing the size of turning area for Yangshan LNG terminal. The outcome indicates that the major axis and minor axis of the turning area can meet the requirement of Q-Max LNG carrier berthing operation and it is suggested to do such maneuvering in some given conditions related to wind, current, tide, visibility and wave.

Effect of Mach number on the acoustic field of 2:1 elliptic-slot jet

2001 ◽  
Vol 105 (1043) ◽  
pp. 9-16 ◽  
Author(s):  
S. B. Verma ◽  
E. Rathakrishnan
Keyword(s):  
Mach Number ◽  
Fundamental Frequency ◽  
Acoustic Field ◽  
Major Axis ◽  
Shock Structure ◽  
Minor Axis ◽  
Noise Levels ◽  
Underexpanded Jets ◽  
Barrel Shock ◽  
Mach Numbers

Abstract The shock-structure and the related acoustic field of underexpanded jets undergoes significant changes as the Mach number Mj is increased. The present investigation is carried out to study the effect of Mach number on an underexpanded 2:1 elliptic-slot jet. Experimental data are presented for fully expanded Mach numbers ranging from 1.3 to 2.0. It is observed that the ‘cross-over’ point at the end of the first cell at low Mach numbers gets replaced by a normal shock at a highly underexpanded condition resulting in the formation of a ‘barrel’ shock along the minor-axis side with a ‘bulb’ shock formed along the major-axis side. The above change in shock structure is accompanied by a related change in the acoustic field. The amplitude of fundamental frequency along the minor-axis side grows with Mj but falls beyond Mj = 1.75. Along the major-axis side, however, the fundamental frequency does not exist at low Mach numbers. It appears at Mj = 1.75 but then falls at Mj = 2.0. The related azimuthal directivity of overall noise levels (OASPL) shows significant changes with Mj.

Comparison of the Flame Characteristics of Turbulent Circular and Elliptic Jets in a Crossflow

2002 ◽  
Vol 124 (3) ◽  
pp. 197-203 ◽  
Author(s):  
S. R. Gollahalli ◽  
D. Pardiwalla
Keyword(s):  
Flame Structure ◽  
Flux Ratio ◽  
Major Axis ◽  
Minor Axis ◽  
No Production ◽  
Sampling System ◽  
Computer Data ◽  
Rate Of Increase ◽  
Jet Velocity ◽  
Lower Limits

This study was directed to understand the coupling effects of the noncircular geometry of the burner and a crossflow on the combustion of gas jets. This paper compares the characteristics of turbulent propane jet flames from circular (diameter=0.45 cm) and elliptic (major axis/minor axis=3) burners of equivalent exit area in a crossflow. The elliptic burner was oriented with its major axis or minor axis aligned with the crossflow. Experiments were conducted in a wind tunnel provided with optical and probe access and capable of wind speeds up to 12.5 m/s. The burners were fabricated with metal tubes. Instrumentation included a Pt-Pt/13% Rh thermocouple, a quartz-probe gas sampling system, chemiluminescent and nondispersive infrared analyzers, a video-recorder, and a computer data acquisition system. The measurements consisted of the upper and lower limits of jet velocity for a stable flame, flame configuration, and visible length. Flame structure data including temperature profiles and concentration profiles of CO2,O2, CO, and NO were obtained in a two-zone flame configuration (at jet to crossflow momentum flux ratio=0.11), where a planar recirculation exists in the wake of the burner tube followed by an axisymmetric tail. The relative emission indicators of CO and NO were estimated from the composition data. Results show that the upper and lower limits of the fuel jet velocity increase with the crossflow velocity for all burners, and the rate of increase is highest for the elliptic burner with its minor axis aligned with the crossflow. That burner configuration also produces the longest flame. The relative emission indicators show that the CO production is lower and NO production is higher with elliptic burners than with circular burners in crossflow.

Quantitative diagenetic analyses of Edmontosaurus regalis (Dinosauria: Hadrosauridae) postcranial elements from the Danek Bonebed, Upper Cretaceous Horseshoe Canyon Formation, Edmonton, Alberta, Canada: implications for allometric studies of fossil organisms

2014 ◽  
Vol 51 (11) ◽  
pp. 1007-1016 ◽  
Author(s):  
Mackenzie Baert ◽  
Michael E. Burns ◽  
Philip J. Currie
Keyword(s):  
Cross Section ◽  
Upper Cretaceous ◽  
Strong Relationship ◽  
Major Axis ◽  
Minor Axis ◽  
Morphological Features ◽  
Fossil Assemblages ◽  
Fossil Vertebrate ◽  
Horseshoe Canyon Formation ◽  
Upper Campanian

For fossil assemblages, quantitative size and shape studies are often complicated by diagenetic distortion. Different vertebrate elements, although subjected to similar burial stresses, exhibit deformations based upon their original shapes; this hypothesis is tested here by quantitatively comparing deformed humeri and femora from the Danek Bonebed (a monodominant Edmontosaurus regalis bonebed from the upper Campanian Horseshoe Canyon Formation in Edmonton, Alberta, Canada) with samples of undeformed humeri and femora from modern and fossil assemblages. Analyses suggest that at the Danek Bonebed a strong relationship exists between element length and circumference despite being distorted by crushing deformation. Major and minor axes of the midshaft cross section, however, were not uniformly distorted. Although their anatomical position did not change, the major axis became longer relative to the minor axis in distorted specimens. A regression based on the undeformed humeri was not able to accurately predict circumference in the Danek humeri. Further study might quantify the deformation of other bones in the Danek Bonebed and could be extended to other assemblages and genera. Caution should be taken when conducting studies in which diagenetic crushing may have altered morphological features of fossil vertebrate remains.

scholarly journals Effect of soaking process on physical properties of mature pepper berries (Piper nigrum L.)

Food Research ◽  
2020 ◽  
Vol 4 (S1) ◽  
pp. 116-123
Author(s):  
A.A.P.N. Megat ◽  
Rosnah Shamsudin ◽  
H. Che Man ◽  
M.E. Ya'acob
Keyword(s):  
Physical Properties ◽  
Water Uptake ◽  
Major Axis ◽  
Minor Axis ◽  
Piper Nigrum ◽  
Uptake Ratio ◽  
Fracture Force ◽  
Brown Colour

This study was carried out to determine the effect of the soaking process on the physical properties of the mature pepper berries. The soaking process was conducted by immersing pepper berries in water. The results showed the dimensions of the pepper berries before soaking was 5.24 mm (minor axis), 5.57 mm (medium axis) and 5.61 mm (major axis). The weight of pepper berries increased from day 1 (13.58%) until day 3 (16.92%) and decreased after day 4 (0.77%) until day 7 of soaking (13.08%). The water uptake ratio of soaked pepper berries increased from 1.14% (day 1) until 1.17% (day 3) and then decreased from 1.01% (day 4) until 0.87% (day 7). The fracture force required to fracture the pericarp was decreased starting from 67.21 N (day 1) decreased until 21.40 N (day 7). The colour of mature pepper berries was changed into black-brown colour (L= 34.16, a= 1.38, b= 1.40).

scholarly journals A complete census of circumgalactic Mg ii at redshift z ≲ 0.5

2021 ◽  
Vol 502 (4) ◽  
pp. 4743-4761 ◽  
Author(s):  
Yun-Hsin Huang ◽  
Hsiao-Wen Chen ◽  
Stephen A Shectman ◽  
Sean D Johnson ◽  
Fakhri S Zahedy ◽  
...  
Keyword(s):  
Rest Frame ◽  
Formation Rate ◽  
Host Galaxies ◽  
Clear Trend ◽  
Stellar Objects ◽  
Star Forming ◽  
Multiple Parameters ◽  
Isolated Galaxies ◽  
Cool Gas ◽  
Gas Accretion

ABSTRACT This paper presents a survey of Mg ii absorbing gas in the vicinity of 380 random galaxies, using 156 background quasi-stellar objects (QSOs) as absorption-line probes. The sample comprises 211 isolated (73 quiescent and 138 star-forming galaxies) and 43 non-isolated galaxies with sensitive constraints for both Mg ii absorption and H α emission. The projected distances span a range from d = 9 to 497 kpc, redshifts of the galaxies range from z = 0.10 to 0.48, and rest-frame absolute B-band magnitudes range from MB = −16.7 to −22.8. Our analysis shows that the rest-frame equivalent width of Mg ii, Wr(2796), depends on halo radius (Rh), B-band luminosity(LB), and stellar mass (Mstar) of the host galaxies, and declines steeply with increasing d for isolated, star-forming galaxies. At the same time, Wr(2796) exhibits no clear trend for either isolated, quiescent galaxies or non-isolated galaxies. In addition, the covering fraction of Mg ii absorbing gas 〈κ〉 is high with 〈κ〉 ≳ 60 per cent at <40 kpc for isolated galaxies and declines rapidly to 〈κ〉 ≈ 0 at d ≳ 100 kpc. Within the gaseous radius, the incidence of Mg ii gas depends sensitively on both Mstar and the specific star formation rate inferred from H α. Different from what is known for massive quiescent haloes, the observed velocity dispersion of Mg ii absorbing gas around star-forming galaxies is consistent with expectations from virial motion, which constrains individual clump mass to $m_{\rm cl} \gtrsim 10^5 \, \rm M_\odot$ and cool gas accretion rate of $\sim 0.7\!-\!2 \, \mathrm{ M}_\odot \, \rm yr^{-1}$. Finally, we find no strong azimuthal dependence of Mg ii absorption for either star-forming or quiescent galaxies. Our results demonstrate that multiple parameters affect the properties of gaseous haloes around galaxies and highlight the need of a homogeneous, absorption-blind sample for establishing a holistic description of chemically enriched gas in the circumgalactic space.

Flow field and acoustics characteristics of elliptical jet

2018 ◽  
Vol 90 (9) ◽  
pp. 1364-1371 ◽  
Author(s):  
S. Manigandan ◽  
Vijayaraja K.
Keyword(s):  
Flow Field ◽  
Large Scale ◽  
Rapid Change ◽  
Supersonic Jet ◽  
Major Axis ◽  
Minor Axis ◽  
Shock Cell ◽  
Potential Core ◽  
Content Type ◽  
Elliptical Jet

Purpose The purpose of this paper is to present the results of mixing promotion and screech frequency of controlled elliptical supersonic jet. Design/methodology/approach Flow field characteristics of low-aspect-ratio elliptical jets are examined at over-expanded, under-expanded and correctly expanded conditions. The tabs are placed at elliptical jet exit along the major and minor axes. Findings The results show that the mixing done by the minor axis is superior to the tabs along major axis. At all pressure ratios, the content of jet noise and the frequency are high for the tabs along the major axis because of increase in the amplitude of screech frequency. Further the tabs along minor axis show a dominance of large-scale vertical structures. In under-expanded conditions, the shock cell shows the rapid change because of the presence of tabs. The tabs along minor axis are making the shock weaker, hence no evidence of axis switching. Practical implications To achieve the greater performance of jet, the authors need to reduce the potential core length of the issuing jet. This can be achieved by implementing different types of tabs at the exit of the nozzle. Originality/value The present paper represents the flow of controlled jet using inverted triangular tabs. By achieving the controlled jet flow, the performance of propulsion systems can be improved. This can be used in systems such as combustion chamber, missile’s noise reduction and thrust vector control.

scholarly journals Extremely metal-poor galaxies with HST/COS: laboratories for models of low-metallicity massive stars and high-redshift galaxies

2019 ◽  
Vol 488 (3) ◽  
pp. 3492-3506 ◽  
Author(s):  
Peter Senchyna ◽  
Daniel P Stark ◽  
Jacopo Chevallard ◽  
Stéphane Charlot ◽  
Tucker Jones ◽  
...  
Keyword(s):  
Massive Stars ◽  
High Redshift ◽  
Formation Rate ◽  
Uv Spectra ◽  
High Redshift Galaxies ◽  
Star Forming ◽  
High Ionization ◽  
Moderate Resolution ◽  
Low Metallicity ◽  
Nearby Galaxies

Abstract Ultraviolet (UV) observations of local star-forming galaxies have begun to establish an empirical baseline for interpreting the rest-UV spectra of reionization-era galaxies. However, existing high-ionization emission line measurements at z > 6 ($\rm W_{C\, {\scriptscriptstyle IV},0}{} \gtrsim 20$ Å) are uniformly stronger than observed locally ($\rm W_{C\, {\scriptscriptstyle IV},0}{} \lesssim 2$ Å), likely due to the relatively high metallicities (Z/Z$\odot$ > 0.1) typically probed by UV surveys of nearby galaxies. We present new HST/COS spectra of six nearby (z < 0.01) extremely metal-poor galaxies (XMPs, Z/Z$\odot$ ≲ 0.1) targeted to address this limitation and provide constraints on the highly uncertain ionizing spectra powered by low-metallicity massive stars. Our data reveal a range of spectral features, including one of the most prominent nebular C iv doublets yet observed in local star-forming systems and strong He ii emission. Using all published UV observations of local XMPs to date, we find that nebular C iv emission is ubiquitous in very high specific star formation rate systems at low metallicity, but still find equivalent widths smaller than those measured in individual lensed systems at z > 6. Our moderate-resolution HST/COS data allow us to conduct an analysis of the stellar winds in a local nebular C iv emitter, which suggests that some of the tension with z > 6 data may be due to existing local samples not yet probing sufficiently high α/Fe abundance ratios. Our results indicate that C iv emission can play a crucial role in the JWST and ELT era by acting as an accessible signpost of very low metallicity (Z/Z$\odot$ < 0.1) massive stars in assembling reionization-era systems.

scholarly journals MUSE Analysis of Gas around Galaxies (MAGG) – I: Survey design and the environment of a near pristine gas cloud at z ≈ 3.5

2019 ◽  
Vol 491 (2) ◽  
pp. 2057-2074 ◽  
Author(s):  
Emma K Lofthouse ◽  
Michele Fumagalli ◽  
Matteo Fossati ◽  
John M O’Meara ◽  
Michael T Murphy ◽  
...  
Keyword(s):  
Survey Design ◽  
Strong Absorption ◽  
Nearby Galaxy ◽  
Star Forming ◽  
Very Large Telescope ◽  
The Galaxy ◽  
First Results ◽  
Statistical Sample ◽  
Galaxy Population ◽  
Gas Cloud

ABSTRACT We present the design, methods, and first results of the MUSE Analysis of Gas around Galaxies (MAGG) survey, a large programme on the Multi-Unit Spectroscopic Explorer (MUSE) instrument at the Very Large Telescope (VLT), which targets 28 z > 3.2 quasars to investigate the connection between optically thick gas and galaxies at z ∼ 3–4. MAGG maps the environment of 52 strong absorption line systems at z ≳ 3, providing the first statistical sample of galaxies associated with gas-rich structures in the early Universe. In this paper, we study the galaxy population around a very metal poor gas cloud at z ≈ 3.53 towards the quasar J124957.23−015928.8. We detect three Lyα emitters within $\lesssim 200~\rm km~s^{-1}$ of the cloud redshift, at projected separations $\lesssim 185~\rm ~kpc$ (physical). The presence of star-forming galaxies near a very metal-poor cloud indicates that metal enrichment is still spatially inhomogeneous at this redshift. Based on its very low metallicity and the presence of nearby galaxies, we propose that the most likely scenario for this Lyman Limit System (LLS) is that it lies within a filament which may be accreting on to a nearby galaxy. Taken together with the small number of other LLSs studied with MUSE, the observations to date show a range of different environments near strong absorption systems. The full MAGG survey will significantly expand this sample and enable a statistical analysis of the link between gas and galaxies to pin down the origin of these diverse environments at z ≈ 3–4.

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