scholarly journals FUV line emission, gas kinematics, and discovery of [Fe XXI] λ1354.1 in the sightline toward a filament in M87

2018 ◽  
Vol 617 ◽  
pp. A123 ◽  
Author(s):  
Michael E. Anderson ◽  
Rashid Sunyaev
Keyword(s):  
Boundary Layer ◽  
Velocity Dispersion ◽  
Line Emission ◽  
Emission Lines ◽  
Bulk Velocity ◽  
Interstellar Gas ◽  
Hot Gas ◽  
Gas Kinematics ◽  
Radio Lobe ◽  
Random Motions

We present new Hubble Space Telescope – Cosmic Origins Spectrograph (HST-COS) G130M spectroscopy which we have obtained for a sightline toward a filament projected 1.9 kpc from the nucleus of M87, near the edge of the inner radio lobe to the east of the nucleus. The combination of the sensitivity of COS and the proximity of M87 allows us to study the structure of this filament in unparalleled detail. We propose that the filament is composed of many cold clumps, each surrounded by an FUV-emitting boundary layer, with the filament having a radius rc ~ 10 pc and the clumps filling the cylinder with a low volume filling factor. The observed velocity dispersion in emission lines from the filament results from the random motions of these clumps within the filament. We have measured fluxes and kinematics for emission lines of Lyα, C II λ1335, and N V λ1238, finding vr = 147 ± 2 km s−1, 138 ± 18 km s−1, and 148−16+14 km s−1 relative to M87, and line broadenings σr = 171 ± 2 km s−1, 189−11+12 km s−1, and 128−17+23 km s−1 respectively. We associate these three lines, as well as archival measurements of Hα, C IV λ1549, and He II λ1640, with a multitemperature boundary layer around clumps which are moving with supersonic random motions in the filament. This boundary layer is a significant coolant of the hot gas. We show that the [C II] λ158 μm flux observed by Herschel-PACS from this region implies the existence of a massive cold (T ~ 103 K) component in the filament which contains significantly more mass (M ~ 8000 M⊙ within our r ≈ 100 pc sightline) than the FUV-emitting boundary layer. It has about the same bulk velocity and velocity dispersion as the boundary layer. We also detect [Fe XXI] λ1354 in emission at 4−5σ. This line is emitted from 1 keV (T ≈ 107 K) plasma, and we use it to measure the bulk radial velocity vr = −92−22+34 km s−1 and velocity dispersion σr = 69−27+79 km s−1 of the plasma at this temperature. In contrast to the intermediate-temperature FUV lines, [Fe XXI] is blueshifted relative to M87 and matches the bulk velocity of a nearby filament to the south. We hypothesize that this line arises from the approaching face of the radio bubble expanding through this sightline, while the filament lies on the receding side of the bubble. A byproduct of our observations is the detection of absorption from interstellar gas in our Galaxy, observed in C II λ1335 and Lyα.

scholarly journals Poor Groups Around Strong Gravitational Lenses

2006 ◽  
Vol 2 (S235) ◽  
pp. 230-230
Author(s):  
Ivelina Momcheva ◽  
Kurtis Williams ◽  
Ann Zabludoff ◽  
Charles Keeton
Keyword(s):  
Galaxy Evolution ◽  
Velocity Dispersion ◽  
Gravitational Lenses ◽  
Local Universe ◽  
Groups Of Galaxies ◽  
Hot Gas ◽  
Gas Kinematics ◽  
The Galaxy ◽  
Group Centroid ◽  
Group Galaxy

AbstractPoor groups are common and interactive environments for galaxies, and thus are important laboratories for studying galaxy evolution. Unfortunately, little is known about groups at z ≥ 0.1, because of the difficulty in identifying them in the first place. Here we present results from our ongoing survey of the environments of strong gravitational lenses, in which we have so far discovered six distant (z ≥ 0.5) groups of galaxies. As in the local Universe, the highest velocity dispersion groups contain a brightest member spatially coincident with the group centroid, whereas lower-dispersion groups tend to have an offset brightest group galaxy. This suggests that higher-dispersion groups are more dynamically relaxed than lower-dispersion groups and that at least some evolved groups exist by z ~ 0.5. We also compare the galaxy and hot gas kinematics with those of similarly distant clusters and of nearby groups.

scholarly journals Features in the Soft X-ray Background

1990 ◽  
Vol 115 ◽  
pp. 146-155
Author(s):  
R. Rothenflug
Keyword(s):  
Energy Resolution ◽  
Line Emission ◽  
Spatial Variations ◽  
Emission Lines ◽  
X Ray ◽  
Hot Gas ◽  
The North ◽  
North Polar ◽  
X Ray Background ◽  
Japanese Group

AbstractThe soft X-ray background is explained in terms of emission coming from hot gas. Most of these soft X-ray data were obtained by proportional counters with a poor energy resolution. Instruments having the capability to resolve lines were only flown by two groups: a GSPC by a Japanese group and a SSD by a french-american collaboration. They both detected the 0 VII line emission coming from the soft X-ray background and so proved the thermal nature of the emission. The implications of these results on possible models for the local hot medium will be discussed. The same detectors observed part of the North Polar Spur. They detected emission lines coming from different species (0 VII,Fe XVII,Ne IX). Spatial variations of line ratios for this object could be due to non-equilibrium ionization effects.

scholarly journals Fabry-Perot Observations of Cen A

1987 ◽  
Vol 127 ◽  
pp. 419-420
Author(s):  
J.J.E. Hayes ◽  
R.A. Schommer ◽  
T.B. Williams
Keyword(s):  
Velocity Dispersion ◽  
Line Emission ◽  
Emission Lines ◽  
Peculiar Galaxy ◽  
Fabry Perot ◽  
Construct Maps ◽  
The Continuum

We present Fabry–Perot spectrophotometry of the well-known peculiar galaxy Cen A (NGC 5128). The observations were carried out using the Rutgers Fabry–Perot system and a CCD as a detector. We scanned the Hα and [NII] (λ6583) emission lines. From these data we were able to construct maps of the continuum, line emission, velocity and velocity dispersion. The velocity maps in both Hα and [NII] have smooth gradients and twists in the line of nodes. The deprojected emission maps strongly resemble emission maps of face-on spirals. We speculate that Cen A is a merger between an elliptical and a spiral.

scholarly journals Autonomous Gaussian decomposition of the Galactic Ring Survey

2019 ◽  
Vol 633 ◽  
pp. A14 ◽  
Author(s):  
M. Riener ◽  
J. Kainulainen ◽  
H. Beuther ◽  
J. D. Henshaw ◽  
J. H. Orkisz ◽  
...  
Keyword(s):  
Velocity Dispersion ◽  
Velocity Structure ◽  
Galactic Plane ◽  
Emission Lines ◽  
Data Sets ◽  
Gas Kinematics ◽  
The Galaxy ◽  
First Results ◽  
Physical Information ◽  
Gaussian Decomposition

The analysis of large molecular line surveys of the Galactic plane is essential for our understanding of the gas kinematics on Galactic scales and, in particular, its link with the formation and evolution of dense structures in the interstellar medium. An approximation of the emission peaks with Gaussian functions allows for an efficient and straightforward extraction of useful physical information contained in the shape and Doppler-shifted frequency of the emission lines contained in these enormous data sets. In this work, we present an overview and the first results of a Gaussian decomposition of the entire Galactic Ring Survey (GRS) 13CO (1–0) data that consists of about 2.3 million spectra. We performed the decomposition with the fully automated GAUSSPY+ algorithm and fitted about 4.6 million Gaussian components to the GRS spectra. These decomposition results enable novel and unexplored ways to interpret and study the gas velocity structure. We discuss the statistics of the fit components and relations between the fitted intensities, velocity centroids, and velocity dispersions. We find that the magnitude of the velocity dispersion values increase towards the inner Galaxy and around the Galactic midplane, which we speculate is partly due to the influence of the Galactic bar and regions with higher non-thermal motions located in the midplane, respectively. We also used our decomposition results to infer global properties of the gas emission and find that the number of fit components used per spectrum is indicative of the amount of structure along the line of sight. We find that the emission lines from regions located on the far side of the Galaxy show increased velocity dispersion values, which are likely due to beam averaging effects. We demonstrate how this trend has the potential to aid in characterising Galactic structure by disentangling emission that belongs to the nearby Aquila Rift molecular cloud from emission that is more likely associated with the Perseus and Outer spiral arms. With this work, we also make our entire decomposition results available.

scholarly journals Near-IR Integral Field Spectroscopy of the central region of NGC 5929

2014 ◽  
Vol 10 (S309) ◽  
pp. 339-339
Author(s):  
Rogemar A. Riffel ◽  
Thaisa Storchi-Bergmann ◽  
Rogério Riffel
Keyword(s):  
Emission Line ◽  
Near Infrared ◽  
Line Emission ◽  
Linear Structure ◽  
Emission Lines ◽  
Line Profiles ◽  
Gas Kinematics ◽  
Systemic Velocity ◽  
Integral Field Spectrograph ◽  
Integral Field

AbstractWe present two-dimensional (2D) near-infrared spectra of the inner 300×300 pc2 of the Seyfert 2 galaxy NGC 5929 at a spatial resolution of ~20 pc obtained with the Gemini Near infrared Integral Field Spectrograph (NIFS). We present 2D maps for the emission line flux distributions and kinematics and report the discovery of a linear structure ~300 pc in extent and of ~50 pc in width oriented perpendicular to the radio jet, showing broadened emission-line profiles.While over most of the field the emission-line profiles have full-widths-at-half-maximum (FWHM) of ~210 km/s, at a linear structure perpendicular do the radio jet the emission-line FWHMs are twice this value, and are due to two velocity components, one blueshifted and the other redshifted relative to the systemic velocity. We attribute these velocities to an outflow from the nucleus which is launched perpendicular to the radio jet. We reported the detection of this peculiar outflow in Riffel, Storchi-Bergmann & Riffel (2014a), where more details of the analysis can be found. Since, NGC 5929 has a Type 2 nucleus, this detection implies that: (1) both ionizing radiation and relativistic particles are escaping through holes in the torus perpendicular to the radio jet; and/or (2) the torus is also outflowing, as proposed by recent models of tori as winds from the outer parts of an accretion flow; or (3) the torus is absent in NGC 5929.At other locations the gas kinematics is dominated by rotation in a disk, although some evidences of interaction of the radio jet with the emitting gas are seen as a broadening of the line profiles at the locations of the radio structures.The flux distributions for the [P ii], [Fe ii], H i and H2 emission lines show that the line emission is more extended along the PA = 60/240^, extending to up to 1.5” to both sides of the nucleus, while to the perpendicular direction (PA = -30/150^) the emission is extended to 0.7” from the nucleus. The flux distributions of all emission lines show a good correlation with radio the radio structures, with the two peak of emission associated to the soutwestern and northeastern radio knots. Some differences are observed among distinct emission lines. While the [Fe ii] and H2 emission peak at the location of the soutwestern radio structure at 0.6” from the nucleus, the H i recombination lines present the their highest fluxes at the location of the northeastern radio hotspot at 0.5” from the nucleus. Another difference is that the H2 emission is less collimated than that for other lines, being more extended perpendicularly to the radio jet. A detailed analysis of the line emission and kinematics will be presented in Riffel, Storchi-Bergmann & Riffel (2014b).

Supernovae and interstellar gas dynamics

1967 ◽  
Vol 31 ◽  
pp. 117-119
Author(s):  
F. D. Kahn ◽  
L. Woltjer
Keyword(s):  
Lower Limit ◽  
High Velocity ◽  
Gas Dynamics ◽  
Interstellar Cloud ◽  
Interstellar Gas ◽  
Random Motions ◽  
Relativistic Particles

The efficiency of the transfer of energy from supernovae into interstellar cloud motions is investigated. A lower limit of about 0·002 is obtained, but values near 0·01 are more likely. Taking all uncertainties in the theory and observations into account, the energy per supernova, in the form of relativistic particles or high-velocity matter, needed to maintain the random motions in the interstellar gas is estimated as 1051·4±1ergs.

scholarly journals Tracing interactions in HCGs through the H I

2000 ◽  
Vol 174 ◽  
pp. 167-173 ◽  
Author(s):  
L. Verdes-Montenegro ◽  
M. S. Yun ◽  
B. A. Williams ◽  
W. K. Huchtmeier ◽  
A. Del Olmo ◽  
...  
Keyword(s):  
Velocity Dispersion ◽  
Group Velocity Dispersion ◽  
Dynamical Evolution ◽  
Compact Groups ◽  
High Group ◽  
X Ray ◽  
Hot Gas ◽  
Isolated Galaxies ◽  
Global Study ◽  
Hickson Compact Groups

AbstractWe present a global study of Hɪ spectral line mapping for 16 Hickson Compact Groups (HCGs) combining new and unpublished VLA data, plus the analysis of the Hɪ content of individual galaxies. Sixty percent of the groups show morphological and kinematical signs of perturbations (from multiple tidal features to concentration of the Hɪ in a single enveloping cloud) and sixty five of the resolved galaxies are found to be Hɪ deficient with respect to a sample of isolated galaxies. In total, 77% of the groups suffer interactions among all its members which provides strong evidence of their reality. We find that dynamical evolution does not always produce Hɪ deficiency, but when this deficiency is observed, it appears to correlate with a high group velocity dispersion and in some cases with the presence of a first-ranked elliptical. The X-ray data available for our sample are not sensitive enough for a comparison with the Hɪ mass; however this study does suggest a correlation between Hɪ deficiency and hot gas since velocity dispersions are known from the literature to correlate with X-ray luminosity.

scholarly journals Resolved Gas Kinematics in a Sample of Low-Redshift High Star-Formation Rate Galaxies

2016 ◽  
Vol 33 ◽  
Author(s):  
Mathew Varidel ◽  
Michael Pracy ◽  
Scott Croom ◽  
Matt S. Owers ◽  
Elaine Sadler
Keyword(s):  
Star Formation ◽  
Velocity Gradient ◽  
Velocity Dispersion ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Local Effect ◽  
Line Of Sight ◽  
Mean Velocity ◽  
Gas Kinematics ◽  
Integral Field Spectroscopy

AbstractWe have used integral field spectroscopy of a sample of six nearby (z ~ 0.01–0.04) high star-formation rate ($\text{SFR} \sim 10\hbox{--}40$$\text{M}_\odot \text{ yr$^{-1}$}$) galaxies to investigate the relationship between local velocity dispersion and star-formation rate on sub-galactic scales. The low-redshift mitigates, to some extent, the effect of beam smearing which artificially inflates the measured dispersion as it combines regions with different line-of-sight velocities into a single spatial pixel. We compare the parametric maps of the velocity dispersion with the Hα flux (a proxy for local star-formation rate), and the velocity gradient (a proxy for the local effect of beam smearing). We find, even for these very nearby galaxies, the Hα velocity dispersion correlates more strongly with velocity gradient than with Hα flux—implying that beam smearing is still having a significant effect on the velocity dispersion measurements. We obtain a first-order non parametric correction for the unweighted and flux weighted mean velocity dispersion by fitting a 2D linear regression model to the spaxel-by-spaxel data where the velocity gradient and the Hα flux are the independent variables and the velocity dispersion is the dependent variable; and then extrapolating to zero velocity gradient. The corrected velocity dispersions are a factor of ~ 1.3–4.5 and ~ 1.3–2.7 lower than the uncorrected flux-weighted and unweighted mean line-of-sight velocity dispersion values, respectively. These corrections are larger than has been previously cited using disc models of the velocity and velocity dispersion field to correct for beam smearing. The corrected flux-weighted velocity dispersion values are σm ~ 20–50 km s−1.

scholarly journals Challenges and Techniques for Simulating Line Emission

Galaxies ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 100 ◽  
Author(s):  
Karen Olsen ◽  
Andrea Pallottini ◽  
Aida Wofford ◽  
Marios Chatzikos ◽  
Mitchell Revalski ◽  
...  
Keyword(s):  
Interstellar Medium ◽  
Emission Line ◽  
Line Emission ◽  
Emission Lines ◽  
Synthetic Spectra ◽  
Recent Advances ◽  
The Future ◽  
Important Quality ◽  
Circumgalactic Medium

Modeling emission lines from the millimeter to the UV and producing synthetic spectra is crucial for a good understanding of observations, yet it is an art filled with hazards. This is the proceedings of “Walking the Line”, a 3-day conference held in 2018 that brought together scientists working on different aspects of emission line simulations, in order to share knowledge and discuss the methodology. Emission lines across the spectrum from the millimeter to the UV were discussed, with most of the focus on the interstellar medium, but also some topics on the circumgalactic medium. The most important quality of a useful model is a good synergy with observations and experiments. Challenges in simulating line emission are identified, some of which are already being worked upon, and others that must be addressed in the future for models to agree with observations. Recent advances in several areas aiming at achieving that synergy are summarized here, from micro-physical to galactic and circum-galactic scale.

scholarly journals Understanding biases in measurements of molecular cloud kinematics using line emission

2020 ◽  
Vol 498 (2) ◽  
pp. 2440-2455
Author(s):  
Yuxuan (宇轩) Yuan (原) ◽  
Mark R Krumholz ◽  
Blakesley Burkhart
Keyword(s):  
Magnetic Field ◽  
Molecular Cloud ◽  
Molecular Clouds ◽  
Velocity Dispersion ◽  
Signal To Noise Ratio ◽  
Line Emission ◽  
Molecular Line ◽  
Velocity Dispersions ◽  
Cloud Kinematics ◽  
Measurement Biases

ABSTRACT Molecular line observations using a variety of tracers are often used to investigate the kinematic structure of molecular clouds. However, measurements of cloud velocity dispersions with different lines, even in the same region, often yield inconsistent results. The reasons for this disagreement are not entirely clear, since molecular line observations are subject to a number of biases. In this paper, we untangle and investigate various factors that drive linewidth measurement biases by constructing synthetic position–position–velocity cubes for a variety of tracers from a suite of self-gravitating magnetohydrodynamic simulations of molecular clouds. We compare linewidths derived from synthetic observations of these data cubes to the true values in the simulations. We find that differences in linewidth as measured by different tracers are driven by a combination of density-dependent excitation, whereby tracers that are sensitive to higher densities sample smaller regions with smaller velocity dispersions, opacity broadening, especially for highly optically thick tracers such as CO, and finite resolution and sensitivity, which suppress the wings of emission lines. We find that, at fixed signal-to-noise ratio, three commonly used tracers, the J = 4 → 3 line of CO, the J = 1 → 0 line of C18O, and the (1,1) inversion transition of NH3, generally offer the best compromise between these competing biases, and produce estimates of the velocity dispersion that reflect the true kinematics of a molecular cloud to an accuracy of $\approx 10{{\ \rm per\ cent}}$ regardless of the cloud magnetic field strengths, evolutionary state, or orientations of the line of sight relative to the magnetic field. Tracers excited primarily in gas denser than that traced by NH3 tend to underestimate the true velocity dispersion by $\approx 20{{\ \rm per\ cent}}$ on average, while low-density tracers that are highly optically thick tend to have biases of comparable size in the opposite direction.

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