scholarly journals How do galaxies build up their spin in the cosmic web?

2014 ◽  
Vol 11 (S308) ◽  
pp. 433-436
Author(s):  
Charlotte Welker ◽  
Yohan Dubois ◽  
Christophe Pichon ◽  
Julien Devriendt ◽  
Sebastien Peirani
Keyword(s):  
Mass Velocity ◽  
Velocity Dispersion ◽  
High Mass ◽  
Spin Orientation ◽  
Star Forming ◽  
Blue Star ◽  
Physical Mechanisms ◽  
Low Mass ◽  
Mass Dependent

AbstractUsing the Horizon-AGN simulation we find a mass dependent spin orientation trend for galaxies: the spin of low-mass, rotation-dominated, blue, star-forming galaxies are preferentially aligned with their closest filament, whereas high-mass, velocity dispersion- supported, red quiescent galaxies tend to possess a spin perpendicular to these filaments. We explore the physical mechanisms driving galactic spin swings and quantify how much mergers and smooth accretion re-orient them relative to their host filaments.

scholarly journals ATLASGAL – Ammonia observations towards the southern Galactic plane

2018 ◽  
Vol 609 ◽  
pp. A125 ◽  
Author(s):  
M. Wienen ◽  
F. Wyrowski ◽  
K. M. Menten ◽  
J. S. Urquhart ◽  
C. M. Walmsley ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Hyperfine Structure ◽  
Optical Depth ◽  
Line Width ◽  
Rotational Temperature ◽  
High Mass ◽  
Mass Star ◽  
Star Forming ◽  
Star Forming Regions ◽  
Low Mass

Context. The initial conditions of molecular clumps in which high-mass stars form are poorly understood. In particular, a more detailed study of the earliest evolutionary phases is needed. The APEX Telescope Large Area Survey of the whole inner Galactic disk at 870 μm, ATLASGAL, has therefore been conducted to discover high-mass star-forming regions at different evolutionary phases. Aims. We derive properties such as velocities, rotational temperatures, column densities, and abundances of a large sample of southern ATLASGAL clumps in the fourth quadrant. Methods. Using the Parkes telescope, we observed the NH3 (1, 1) to (3, 3) inversion transitions towards 354 dust clumps detected by ATLASGAL within a Galactic longitude range between 300° and 359° and a latitude within ± 1.5°. For a subsample of 289 sources, the N2H+ (1–0) line was measured with the Mopra telescope. Results. We measured a median NH3 (1, 1) line width of ~ 2 km s-1, rotational temperatures from 12 to 28 K with a mean of 18 K, and source-averaged NH3 abundances from 1.6 × 10-6 to 10-8. For a subsample with detected NH3 (2, 2) hyperfine components, we found that the commonly used method to compute the (2, 2) optical depth from the (1, 1) optical depth and the (2, 2) to (1, 1) main beam brightness temperature ratio leads to an underestimation of the rotational temperature and column density. A larger median virial parameter of ~ 1 is determined using the broader N2H+ line width than is estimated from the NH3 line width of ~ 0.5 with a general trend of a decreasing virial parameter with increasing gas mass. We obtain a rising NH3 (1, 1)/N2H+ line-width ratio with increasing rotational temperature. Conclusions. A comparison of NH3 line parameters of ATLASGAL clumps to cores in nearby molecular clouds reveals smaller velocity dispersions in low-mass than high-mass star-forming regions and a warmer surrounding of ATLASGAL clumps than the surrounding of low-mass cores. The NH3 (1, 1) inversion transition of 49% of the sources shows hyperfine structure anomalies. The intensity ratio of the outer hyperfine structure lines with a median of 1.27 ± 0.03 and a standard deviation of 0.45 is significantly higher than 1, while the intensity ratios of the inner satellites with a median of 0.9 ± 0.02 and standard deviation of 0.3 and the sum of the inner and outer hyperfine components with a median of 1.06 ± 0.02 and standard deviation of 0.37 are closer to 1.

scholarly journals D 2 O and HDS in the coma of 67P/Churyumov–Gerasimenko

2017 ◽  
Vol 375 (2097) ◽  
pp. 20160253 ◽  
Author(s):  
K. Altwegg ◽  
H. Balsiger ◽  
J. J. Berthelier ◽  
A. Bieler ◽  
U. Calmonte ◽  
...  
Keyword(s):  
High Ratio ◽  
High Mass ◽  
Mass Star ◽  
Deuterated Water ◽  
Star Forming ◽  
Star Forming Regions ◽  
Upper Limits ◽  
Rosetta Mission ◽  
Low Mass ◽  
Grain Surface

The European Rosetta mission has been following comet 67P/Churyumov–Gerasimenko for 2 years, studying the nucleus and coma in great detail. For most of these 2 years the Rosetta Orbiter Sensor for Ion and Neutral Analysis (ROSINA) has analysed the volatile part of the coma. With its high mass resolution and sensitivity it was able to not only detect deuterated water HDO, but also doubly deuterated water, D 2 O and deuterated hydrogen sulfide HDS. The ratios for [HDO]/[H 2 O], [D 2 O]/[HDO] and [HDS]/[H 2 S] derived from our measurements are (1.05 ± 0.14) × 10 −3 , (1.80 ± 0.9) × 10 −2 and (1.2 ± 0.3) × 10 −3 , respectively. These results yield a very high ratio of 17 for [D 2 O]/[HDO] relative to [HDO]/[H 2 O]. Statistically one would expect just 1/4. Such a high value can be explained by cometary water coming unprocessed from the presolar cloud, where water is formed on grains, leading to high deuterium fractionation. The high [HDS]/[H 2 S] ratio is compatible with upper limits determined in low-mass star-forming regions and also points to a direct correlation of cometary H 2 S with presolar grain surface chemistry. This article is part of the themed issue ‘Cometary science after Rosetta’.

scholarly journals Low levels of methanol deuteration in the high-mass star-forming region NGC 6334I

2018 ◽  
Vol 615 ◽  
pp. A88 ◽  
Author(s):  
Eva G. Bøgelund ◽  
Brett A. McGuire ◽  
Niels F. W. Ligterink ◽  
Vianney Taquet ◽  
Crystal L. Brogan ◽  
...  
Keyword(s):  
High Sensitivity ◽  
High Mass ◽  
Galactic Centre ◽  
Mass Star ◽  
Star Forming ◽  
Star Forming Regions ◽  
Low Mass ◽  
Low Levels ◽  
Grain Surface ◽  
Physical And Chemical

Context. The abundance of deuterated molecules in a star-forming region is sensitive to the environment in which they are formed. Deuteration fractions, in other words the ratio of a species containing D to its hydrogenated counterpart, therefore provide a powerful tool for studying the physical and chemical evolution of a star-forming system. While local low-mass star-forming regions show very high deuteration ratios, much lower fractions are observed towards Orion and the Galactic centre. Astration of deuterium has been suggested as a possible cause for low deuteration in the Galactic centre. Aims. We derive methanol deuteration fractions at a number of locations towards the high-mass star-forming region NGC 6334I, located at a mean distance of 1.3 kpc, and discuss how these can shed light on the conditions prevailing during its formation. Methods. We use high sensitivity, high spatial and spectral resolution observations obtained with the Atacama Large Millimeter/ submillimeter Array to study transitions of the less abundant, optically thin, methanol-isotopologues: 13CH3OH, CH318OH, CH2DOH and CH3OD, detected towards NGC 6334I. Assuming local thermodynamic equilibrium (LTE) and excitation temperatures of ~120–330 K, we derive column densities for each of the species and use these to infer CH2DOH/CH3OH and CH3OD/CH3OH fractions. Results. We derive column densities in a range of (0.8–8.3) × 1017 cm−2 for 13CH3OH, (0.13–3.4) × 1017 cm−2 for CH318OH, (0.03–1.63) × 1017 cm−2 for CH2DOH and (0.15–5.5) × 1017 cm−2 for CH3OD in a ~1″ beam. Interestingly, the column densities of CH3OD are consistently higher than those of CH2DOH throughout the region by factors of 2–15. We calculate the CH2DOH to CH3OH and CH3OD to CH3OH ratios for each of the sampled locations in NGC 6334I. These values range from 0.03% to 0.34% for CH2DOH and from 0.27% to 1.07% for CH3OD if we use the 13C isotope of methanol as a standard; using the 18 O-methanol as a standard, decreases the ratios by factors of between two and three. Conclusions. All regions studied in this work show CH2DOH/CH3OH as well as CH2DOH/CH3OD values that are considerably lower than those derived towards low-mass star-forming regions and slightly lower than those derived for the high-mass star-forming regions in Orion and the Galactic centre. The low ratios indicate a grain surface temperature during formation ~30 K, for which the efficiency of the formation of deuterated species is significantly reduced. Therefore, astration of deuterium in the Galactic centre cannot be the explanation for its low deuteration ratio but rather the high temperatures characterising the region.

scholarly journals An X-Ray View of Interacting Binaries Outside The Galaxy

2004 ◽  
Vol 194 ◽  
pp. 3-6
Author(s):  
Andrea H. Prestwich
Keyword(s):  
Supernova Remnants ◽  
Luminosity Function ◽  
Local Group ◽  
Spiral Galaxies ◽  
High Mass ◽  
X Ray ◽  
Star Forming ◽  
Star Forming Regions ◽  
Low Mass ◽  
X Ray Binaries

AbstractChandra and XMM-Newton are revolutionizing our understanding of compact binaries in external galaxies, allowing us to study sources in detail in Local Group Galaxies and study populations in more distant systems. In M31 the X-ray luminosity function depends on the local stellar population in the sense that areas with active star formation have more high luminosity sources, and a higher overall source density (Kong. Di Stefano. Garcia, & Greiner 2003). This result is also true in galaxies outside the Local Group; starburst galaxies have flatter X-ray luminosity functions than do spiral galaxies which are in turn flatter than elliptical galaxies. These observational results suggest that the high end of the luminosity function in star forming regions is dominated by short-lived high mass X-ray binaries.In Chandra Cycle 2 we started a Large Project to survey a sample of 11 nearby (< 10Mpc) face-on spiral galaxies. We find that sources can be approximately classified on the basis of their X-ray color into low mass X-ray binaries, high mass X-ray binaries and supersoft sources. There is an especially interesting class of source that has X-ray colors softer (“redder”) than a typical low mass X-ray binary source, but not so extreme as supersoft sources. Most of these are probably X-ray bright supernova remnants, but some may be a new type of black hole accretor. Finally, when we construct a luminosity function of sources selecting only sources with low mass X-ray binary colors (removing soft sources) we find that there is a dip or break probably associated with the Eddington luminosity for a neutron star.

scholarly journals Search for radio jets from massive young stellar objects

2020 ◽  
Vol 645 ◽  
pp. A29
Author(s):  
Ü. Kavak ◽  
Á. Sánchez-Monge ◽  
A. López-Sepulcre ◽  
R. Cesaroni ◽  
F. F. S. van der Tak ◽  
...  
Keyword(s):  
Field Of View ◽  
Radio Continuum ◽  
High Mass ◽  
Mass Star ◽  
Low Mass Stars ◽  
Star Forming ◽  
Radio Jets ◽  
Star Forming Regions ◽  
Nonthermal Emission ◽  
Low Mass

Context. Recent theoretical and observational studies debate the similarities of the formation process of high- (>8 M⊙) and low-mass stars. The formation of low-mass stars is directly associated with the presence of disks and jets. Theoretical models predict that stars with masses up to 140 M⊙ can be formed through disk-mediated accretion in disk-jet systems. According to this scenario, radio jets are expected to be common in high-mass star-forming regions. Aims. We aim to increase the number of known radio jets in high-mass star-forming regions by searching for radio-jet candidates at radio continuum wavelengths. Methods. We used the Karl G. Jansky Very Large Array (VLA) to observe 18 high-mass star-forming regions in the C band (6 cm, ≈1′′.0 resolution) and K band (1.3 cm, ≈0′′.3 resolution). We searched for radio-jet candidates by studying the association of radio continuum sources with shock activity signs (e.g., molecular outflows, extended green objects, and maser emission). Our VLA observations also targeted the 22 GHz H2O and 6.7 GHz CH3OH maser lines. Results. We have identified 146 radio continuum sources, 40 of which are located within the field of view of both images (C and K band maps). We derived the spectral index, which is consistent with thermal emission (between − 0.1 and + 2.0) for 73% of these sources. Based on the association with shock-activity signs, we identified 28 radio-jet candidates. Out of these, we identified 7 as the most probable radio jets. The radio luminosity of the radio-jet candidates is correlated with the bolometric luminosity and the outflow momentum rate. About 7–36% of the radio-jet candidates are associated with nonthermal emission. The radio-jet candidates associated with 6.7 GHz CH3OH maser emission are preferentially thermal winds and jets, while a considerable fraction of radio-jet candidates associated with H2O masers show nonthermal emission that is likely due to strong shocks. Conclusions. About 60% of the radio continuum sources detected within the field of view of our VLA images are potential radio jets. The remaining sources could be compact H II regions in their early stages of development, or radio jets for which we currently lack further evidence of shock activity. Our sample of 18 regions is divided into 8 less evolved infrared-dark regions and 10 more evolved infrared-bright regions. We found that ≈71% of the identified radio-jet candidates are located in the more evolved regions. Similarly, 25% of the less evolved regions harbor one of the most probable radio jets, while up to 50% of the more evolved regions contain one of these radio-jet candidates. This suggests that the detection of radio jets in high-mass star-forming regions is more likely in slightly more evolved regions.

scholarly journals No missing photons for reionization: moderate ionizing photon escape fractions from the FIRE-2 simulations

2020 ◽  
Vol 498 (2) ◽  
pp. 2001-2017 ◽  
Author(s):  
Xiangcheng Ma ◽  
Eliot Quataert ◽  
Andrew Wetzel ◽  
Philip F Hopkins ◽  
Claude-André Faucher-Giguère ◽  
...  
Keyword(s):  
Large Fraction ◽  
High Mass ◽  
Population Synthesis ◽  
Single Star ◽  
Star Forming ◽  
Star Forming Regions ◽  
Sample Average ◽  
Dense Shell ◽  
Low Mass ◽  
Dust Attenuation

ABSTRACT We present the escape fraction of hydrogen ionizing photons (fesc) from a sample of 34 high-resolution cosmological zoom-in simulations of galaxies at z ≥ 5 in the Feedback in Realistic Environments project, post-processed with a Monte Carlo radiative transfer code for ionizing radiation. Our sample consists of 8500 haloes in Mvir ∼ 108–$10^{12}\, M_{\odot }$ (M* ∼ 104–$10^{10}\, M_{\odot }$) at z = 5–12. We find the sample average 〈fesc〉increases with halo mass for Mvir ∼ 108–$10^{9.5}\, M_{\odot }$, becomes nearly constant for 109.5–$10^{11}\, M_{\odot }$, and decreases at ${\gtrsim}10^{11}\, M_{\odot }$. Equivalently, 〈fesc〉 increases with stellar mass up to $M_{\ast }\sim 10^8\, M_{\odot }$ and decreases at higher masses. Even applying single-star stellar population synthesis models, we find a moderate 〈fesc〉 ∼ 0.2 for galaxies at $M_{\ast }\sim 10^8\, M_{\odot }$. Nearly half of the escaped ionizing photons come from stars 1–3 Myr old and the rest from stars 3–10 Myr old. Binaries only have a modest effect, boosting 〈fesc〉 by ∼25–35 per cent and the number of escaped photons by 60–80 per cent. Most leaked ionizing photons are from vigorously star-forming regions that usually contain a feedback-driven kpc-scale superbubble surrounded by a dense shell. The shell is forming stars while accelerated, so new stars formed earlier in the shell are already inside the shell. Young stars in the bubble and near the edge of the shell can fully ionize some low-column-density paths pre-cleared by feedback, allowing a large fraction of their ionizing photons to escape. The decrease of 〈fesc〉 at the high-mass end is due to dust attenuation, while at the low-mass end, 〈fesc〉 decreases owing to inefficient star formation and hence feedback. At fixed mass, 〈fesc〉 tends to increase with redshift. Although the absolute 〈fesc〉does not fully converge with resolution in our simulations, the mass- and redshift-dependence of 〈fesc〉 is likely robust. Our simulations produce sufficient ionizing photons for cosmic reionization.

scholarly journals Filaments and ridges in Vela C revealed byHerschel: from low-mass to high-mass star-forming sites

2011 ◽  
Vol 533 ◽  
pp. A94 ◽  
Author(s):  
T. Hill ◽  
F. Motte ◽  
P. Didelon ◽  
S. Bontemps ◽  
V. Minier ◽  
...  
Keyword(s):  
High Mass ◽  
Mass Star ◽  
Star Forming ◽  
Low Mass

scholarly journals Molecular analysis of a high-mass prestellar core candidate in W43-MM1

2019 ◽  
Vol 626 ◽  
pp. A132 ◽  
Author(s):  
J. Molet ◽  
N. Brouillet ◽  
T. Nony ◽  
A. Gusdorf ◽  
F. Motte ◽  
...  
Keyword(s):  
Star Formation ◽  
High Mass ◽  
Continuum Emission ◽  
Mass Star ◽  
Star Forming ◽  
Prestellar Cores ◽  
Low Mass ◽  
Lower Temperature ◽  
Diagram Analysis ◽  
The Continuum

Context. High-mass analogues of low-mass prestellar cores are searched for to constrain the models of high-mass star formation. Several high-mass cores, at various evolutionary stages, have been recently identified towards the massive star-forming region W43-MM1 and amongst them a high-mass prestellar core candidate. Aims. We aim to characterise the chemistry in this high-mass prestellar core candidate, referred to as W43-MM1 core #6, and its environment. Methods. Using ALMA high-spatial resolution data of W43-MM1, we have studied the molecular content of core #6 and a neighbouring high-mass protostellar core, referred to as #3, which is similar in size and mass to core #6. We first subtracted the continuum emission using a method based on the density distribution of the intensities on each pixel. Then, from the distribution of detected molecules, we identified the molecules centred on the prestellar core candidate (core #6) and those associated to shocks related to outflows and filament formation. Then we constrained the column densities and temperatures of the molecules detected towards the two cores. Results. While core #3 appears to contain a hot core with a temperature of about 190 K, core #6 seems to have a lower temperature in the range from 20 to 90 K from a rotational diagram analysis. We have considered different source sizes for core #6 and the comparison of the abundances of the detected molecules towards the core with various interstellar sources shows that it is compatible with a core of size 1000 au with T = 20−90 K or a core of size 500 au with T ~ 80 K. Conclusions. Core #6 of W43-MM1 remains one of the best high-mass prestellar core candidates even if we cannot exclude that it is at the very beginning of the protostellar phase of high-mass star formation.

scholarly journals Submillimetre polarimetric observations of magnetic fields in star-forming regions

2007 ◽  
Vol 3 (S243) ◽  
pp. 63-70
Author(s):  
Rachel L. Curran ◽  
Antonio Chrysostomou ◽  
Brenda C. Matthews
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Cumulative Distribution ◽  
High Mass ◽  
Continuum Emission ◽  
Field Pattern ◽  
Star Forming ◽  
Star Forming Regions ◽  
Low Mass ◽  
The Magnetic Field

AbstractSubmillimetre imaging polarimetry is one of the most powerful tools at present for studying magnetic fields in star-forming regions, and the only way to gain significant information on the structure of these fields. We present analysis of the largest sample (to date) of both high- and low-mass star-forming regions observed using this technique. A variety of magnetic field morphologies are observed, with no single field morphology favoured. Both the continuum emission morphologies and the field morphologies are generally more complex for the high-mass sample than the low-mass sample. The large scale magnetic field (observed with the JCMT; 14″ resolution) of NGC1333 IRAS2 is interpreted to be weak (compared to the energetic contributions due to turbulence) from the random field pattern observed. On smaller scales (observed with the BIMA array; 3″ resolution) the field is observed to be almost radial, consistent with the polarisation nulls in the JCMT data – suggesting that on smaller scales, the field may be more important to the star formation process. An analysis of the magnetic field direction and the jet/outflow axis is also discussed. Cumulative distribution functions of the difference between the mean position angle of the magnetic field vectors and the jet/outflow axis reveal no correlation. However, visual inspection of the maps reveal alignment of the magnetic field and jet/outflow axis in 7 out of 15 high-mass regions and 3 out of 8 low-mass regions.

scholarly journals VLBI multi-epoch water maser observations toward massive protostars

2012 ◽  
Vol 8 (S287) ◽  
pp. 377-385 ◽  
Author(s):  
José M. Torrelles ◽  
José F. Gómez ◽  
Nimesh A. Patel ◽  
Salvador Curiel ◽  
Guillem Anglada ◽  
...  
Keyword(s):  
Massive Star ◽  
High Mass ◽  
Mass Star ◽  
Star Forming ◽  
Star Forming Regions ◽  
Central Engine ◽  
Dynamic Scenario ◽  
Low Mass ◽  
Cepheus A ◽  
Water Maser

AbstractVLBI multi-epoch water maser observations are a powerful tool to study the gas very close to the central engine responsible for the phenomena associated with the early evolution of massive protostars. In this paper we present a summary of the main observational results obtained toward the massive star-forming regions of Cepheus A and W75N. These observations revealed unexpected phenomena in the earliest stages of evolution of massive objects (e.g., non-collimated “short-lived” pulsed ejections in different massive protostars), and provided new insights in the study of the dynamic scenario of the formation of high-mass stars (e.g., simultaneous presence of a jet and wide-angle outflow in the massive object Cep A HW2, similar to what is observed in low-mass protostars). In addition, with these observations it has been possible to identify new, previously unseen centers of high-mass star formation through outflow activity.

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