scholarly journals The velocity field of the Lyra complex

2020 ◽  
Vol 633 ◽  
pp. A108 ◽  
Author(s):  
M. Girardi ◽  
W. Boschin ◽  
S. De Grandi ◽  
M. Longhetti ◽  
S. Clavico ◽  
...  
Keyword(s):  
Velocity Field ◽  
High Velocity ◽  
Major Axis ◽  
Dynamical Analysis ◽  
Cluster Assembly ◽  
X Ray ◽  
Radio Data ◽  
The Galaxy ◽  
A Minor ◽  
Complex Scenario

Context. The formation of cosmic structures culminates with the assembly of galaxy clusters, a process that is quite different from cluster to cluster. Aims. We present the study of the structure and dynamics of the Lyra complex, consisting of the two clusters RXC J1825.3+3026 and CIZA J1824.1+3029, which was very recently studied by using both X-ray and radio data. Methods. This is the first analysis based on the kinematics of member galaxies. New spectroscopic data for 285 galaxies were acquired at the Italian Telescopio Nazionale Galileo and were used in combination with PanSTARRS photometry. The result of our member selection is a sample of 198 galaxies. Results. For RXCJ1825 and CIZAJ1824 we report the redshifts, z = 0.0645 and z = 0.0708, the first estimates of velocity dispersion, σv = 995+131−125 km s−1 and σv = 700 ± 50 km s−1, and of dynamical mass, M200 = 1.1 ± 0.4  × 1015 M⊙ and M200 = 4 ± 0.1 × 1014 M⊙. The past assembly of RXCJ1825 is traced by the two dominant galaxies, which are both aligned with the major axis of the galaxy distribution along the east–west direction, and by a minor northeast substructure. We also detect a quite peculiar high velocity field in the southwest region of the Lyra complex. This feature is likely related to a very luminous galaxy, which is characterized by a high velocity. This galaxy is suggested to be the central galaxy of a group that is in interaction with RXCJ1825 according to very recent studies based on X-ray and radio data. The redshift of the whole Lyra complex is z = 0.067. Assuming that the redshift difference between RXCJ1825 and CIZAJ1824 is due to the relative kinematics, the projected distance between the cluster centers is D ∼ 1.3 Mpc and the line–of–sight velocity difference is ∼1750 km s−1. A dynamical analysis of the system shows that the two clusters are likely to be gravitationally bound in a pre-merger phase, and that CIZAJ1824 is moving toward RXCJ1825. Conclusions. Our results corroborate a picture where the Lyra region is the place of a very complex scenario of cluster assembly.

scholarly journals An unusual transient following the short GRB 071227

2019 ◽  
Vol 489 (1) ◽  
pp. 13-27
Author(s):  
R A J Eyles ◽  
P T O’Brien ◽  
K Wiersema ◽  
R L C Starling ◽  
B P Gompertz ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Thermal Emission ◽  
Chemical Properties ◽  
Major Axis ◽  
Optical Observations ◽  
X Ray ◽  
Very Large Telescope ◽  
The Galaxy ◽  
Simple Extrapolation ◽  
Emission Models

ABSTRACT We present X-ray and optical observations of the short duration gamma-ray burst GRB 071227 and its host at z = 0.381, obtained using Swift, Gemini South, and the Very Large Telescope. We identify a short-lived and moderately bright optical transient, with flux significantly in excess of that expected from a simple extrapolation of the X-ray spectrum at 0.2–0.3 d after burst. We fit the SED with afterglow models allowing for high extinction and thermal emission models that approximate a kilonova to assess the excess’ origins. While some kilonova contribution is plausible, it is not favoured due to the low temperature and high luminosity required, implying superluminal expansion and a large ejecta mass of ∼0.1 M$\odot$. We find, instead, that the transient is broadly consistent with power-law spectra with additional dust extinction of E(B − V) ∼ 0.4 mag, although a possibly thermal excess remains in the z band. We investigate the host, a spiral galaxy with an edge-on orientation, resolving its spectrum along its major axis to construct the galaxy rotation curve and analyse the star formation and chemical properties. The integrated host emission shows evidence for high extinction, consistent with the afterglow findings. The metallicity and extinction are consistent with previous studies of this host and indicate the galaxy is a typical, but dusty, late-type SGRB host.

scholarly journals The Hertzsprung-Russell Diagram of Metal-Poor Disk Stars

1978 ◽  
Vol 80 ◽  
pp. 273-276
Author(s):  
Sidney van den Bergh
Keyword(s):  
Velocity Field ◽  
Globular Cluster ◽  
High Velocity ◽  
Population Model ◽  
Open Cluster ◽  
Ultraviolet Excess ◽  
Red Giants ◽  
The Sun ◽  
The Galaxy ◽  
Red Giant

A quarter of a century ago Keenan and Keller (1953) showed that the majority of high-velocity stars near the Sun outline a Hertzsprung-Russell diagram similar to that of old Population I. This result, which did not appear to fit into Baade's (1944) two-population model of the Galaxy was ignored (except by Roman 1965) for the next two decades. Striking confirmation of the results of Keenan and Keller was, however, obtained by Hartwick and Hesser (1972). Their work appears to show that high-velocity field stars with an ultraviolet excess (which measures Fe/H) of δ(U-B) ≃ +0m.11 lie on a red giant branch that is more than a magnitude fainter than the giant branch of the strong-lined globular cluster 47 Tuc for which δ(U-B) ≃ +0m.10. Furthermore Demarque and McClure (1977) show that the red giants in the old metal poor [δ(U-B) ≃ +0m.11] open cluster NGC 2420 are significantly fainter than are those in 47 Tuc. Calculations by these authors show that the observed differences between the giants in 47 Tuc and in NGC 2420 can be explained if either (1) 47 Tuc is richer in helium than NGC 2420 by ΔY ≃ 0.1 or (2) if 47 Tuc has a ten times lower value of Z(CNO) than does NGC 2420.

scholarly journals CO in NGC 5055

1987 ◽  
Vol 115 ◽  
pp. 659-660
Author(s):  
L.E.B. Johansson ◽  
R. S. Booth
Keyword(s):  
Velocity Field ◽  
Radial Distribution ◽  
Rotation Curve ◽  
A Priori ◽  
Optical Emission ◽  
Major Axis ◽  
Rotation Curves ◽  
Fitting Procedure ◽  
The Galaxy ◽  
Co Emission

The flocculent spiral galaxy NGC 5055 has been mapped along the major axis in the 12CO (J = 1-0) line using the Onsala 20-m telescope (HPBW = 33″). Figure 1, which gives the spatial velocity diagram of CO emission on the major axis with observed Hα velocities (Kruit and Bosma, 1978) superimposed, seems to imply higher velocities of the regions responsible for the optical emission. Taking into account the cruder spatial resolution of the CO observations, this effect is expected in a region where the rotation curve rises rapidly provided that the CO emission increases toward the centre. Figure 2 shows the rotation velocities for the eastern and western parts of the galaxy separately, as observed in Hα and CO. For CO we only give the portion of the rotation curve which is accurately determined, i.e. where it is relatively flat. The CO velocities in this region agree closely with those observed in HI (Bosma, 1978). These data suggest a difference of 10-20 km s−1 between the Hα and CO velocities at a distance of ∼ 60″ from the centre. The radial distribution of the CO emission, also indicated in Fig. 2, is defined by an iterative fitting procedure to the observed line profiles (see Scoville et al. 1983). This procedure requests an a priori knowledge of the velocity field, here assumed to be defined by the Hα data inside a radius of 60″. However, the shapes of the observed spectra and “best fit” model profiles differ significantly in some cases, again indicating that the Hα velocities do not apply to the molecular gas. The derived radial distribution of the CO emission is dependent on the assumed velocity field; however, the gross characteristics are retained for more feasible rotation curves (i.e. rotation curves giving better fits to the observed profiles).

scholarly journals The AGNIFS survey: distribution and excitation of the hot molecular and ionised gas in the inner kpc of nearby AGN hosts

2021 ◽  
Author(s):  
R A Riffel ◽  
T Storchi-Bergmann ◽  
R Riffel ◽  
M Bianchin ◽  
N L Zakamska ◽  
...  
Keyword(s):  
Major Axis ◽  
Thermal Processes ◽  
X Ray ◽  
Accretion Rates ◽  
The Galaxy ◽  
Dusty Torus ◽  
Extended Emission ◽  
The Continuum

Abstract We use the Gemini NIFS instrument to map the H2 2.1218 μm and Brγ flux distributions in the inner 0.04–2 kpc of a sample of 36 nearby active galaxies (0.001 ≲ z ≲ 0.056) at spatial resolutions from 4 to 250 pc. We find extended emission in 34 galaxies. In ∼55 per cent of them, the emission in both lines is most extended along the galaxy major axis, while in the other 45 per cent the extent follows a distinct orientation. The emission of H2 is less concentrated than that of Brγ, presenting a radius that contains half of the flux 60 per cent greater, on average. The H2 emission is driven by thermal processes – X-ray heating and shocks – at most locations for all galaxies, where $0.4<\rm H_2/Br\gamma <6$. For regions where H2/Brγ > 6 (seen in 40 per cent of the galaxies), shocks are the main H2 excitation mechanism, while in regions with H2/Brγ < 0.4 (25 per cent of the sample) the H2 emission is produced by fluorescence. The only difference we found between type 1 and type 2 AGN was in the nuclear emission-line equivalent widths, that are smaller in type 1 than in type 2 due to a larger contribution to the continuum from the hot dusty torus in the former. The gas masses in the inner 125 pc radius are in the range 101 − 104 M⊙ for the hot H2 and 103 − 106 M⊙ for the ionised gas and would be enough to power the AGN in our sample for 105 − 108 yr at their current accretion rates.

scholarly journals Active gas features in three HSC-SSP CAMIRA clusters revealed by high angular resolution analysis of MUSTANG-2 SZE and XXL X-ray observations

2020 ◽  
Vol 501 (2) ◽  
pp. 1701-1732
Author(s):  
Nobuhiro Okabe ◽  
Simon Dicker ◽  
Dominique Eckert ◽  
Tony Mroczkowski ◽  
Fabio Gastaldello ◽  
...  
Keyword(s):  
Large Scale ◽  
Angular Resolution ◽  
Major Axis ◽  
High Angular Resolution ◽  
X Ray ◽  
Spatially Resolved ◽  
Sunyaev Zel'dovich Effect ◽  
Major Merger ◽  
Resolution Analysis ◽  
A Minor

ABSTRACT We present results from simultaneous modelling of high angular resolution GBT/MUSTANG-2 90 GHz Sunyaev–Zel’dovich effect (SZE) measurements and XMM-XXL X-ray images of three rich galaxy clusters selected from the HSC-SSP Survey. The combination of high angular resolution SZE and X-ray imaging enables a spatially resolved multicomponent analysis, which is crucial to understand complex distributions of cluster gas properties. The targeted clusters have similar optical richnesses and redshifts, but exhibit different dynamical states in their member galaxy distributions: a single-peaked cluster, a double-peaked cluster, and a cluster belonging to a supercluster. A large-scale residual pattern in both regular Compton-parameter y and X-ray surface brightness distributions is found in the single-peaked cluster, indicating a sloshing mode. The double-peaked cluster shows an X-ray remnant cool core between two SZE peaks associated with galaxy concentrations. The temperatures of the two peaks reach ∼20–30 keV in contrast to the cool core component of ∼2 keV, indicating a violent merger. The main SZE signal for the supercluster is elongated along a direction perpendicular to the major axis of the X-ray core, suggesting a minor merger before core passage. The SX and y distributions are thus perturbed at some level, regardless of the optical properties. We find that the integrated Compton y parameter and the temperature for the major merger are boosted from those expected by the weak-lensing mass and those for the other two clusters show no significant deviations, which is consistent with predictions of numerical simulations.

scholarly journals Dynamical Models of the Maser in NGC 4258

1997 ◽  
Vol 159 ◽  
pp. 402-405
Author(s):  
J.M. Moran
Keyword(s):  
Linear Dependence ◽  
High Velocity ◽  
Major Axis ◽  
Line Of Sight ◽  
Velocity Versus ◽  
Dynamical Models ◽  
Maser Emission ◽  
Systemic Velocity ◽  
The Galaxy ◽  
Dynamical Connection

The presence of two quasars symmetrically displaced from the nucleus of the galaxy NGC 4258 (Pietsch et al. 1994) has given rise to some speculation that they might have some dynamical connection with the high-velocity maser emission seen in the nucleus (Burbidge 1996; Ozernoy 1996). The case that the masers define a simple Keplerian disk is very compelling; nonetheless, it is instructive to investigate whether any other dynamical models could fit the available data.The evidence that the masers define a thin Keplerian disk can be found in Miyoshi et al. (1995) and Moran et al. (1995). Some of the relevant data are shown elsewhere in this volume (Fig. 2 of Greenhill’s paper). The basic analysis is as follows. The features near the systemic velocity of 470km s−1 show a linear dependence of line-of-sight velocity versus distance along the major axis, while the redshifted and blueshifted high-velocity features show a nearly Keplerian dependence with distance.

Galactic orbits of stars

1966 ◽  
Vol 25 ◽  
pp. 93-97
Author(s):  
Richard Woolley
Keyword(s):  
Globular Cluster ◽  
Potential Field ◽  
High Velocity ◽  
Velocity Vector ◽  
Variable Stars ◽  
The Sun ◽  
Proper Motions ◽  
Rr Lyrae ◽  
The Galaxy

It is now possible to determine proper motions of high-velocity objects in such a way as to obtain with some accuracy the velocity vector relevant to the Sun. If a potential field of the Galaxy is assumed, one can compute an actual orbit. A determination of the velocity of the globular clusterωCentauri has recently been completed at Greenwich, and it is found that the orbit is strongly retrograde in the Galaxy. Similar calculations may be made, though with less certainty, in the case of RR Lyrae variable stars.

scholarly journals X-ray and Neutron Study on the Structure of Hydrous SiO2 Glass up to 10 GPa

Minerals ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 84 ◽  
Author(s):  
Satoru Urakawa ◽  
Toru Inoue ◽  
Takanori Hattori ◽  
Asami Sano-Furukawa ◽  
Shinji Kohara ◽  
...  
Keyword(s):  
Oxide Glasses ◽  
Void Space ◽  
X Ray Diffraction ◽  
Amorphous Sio2 ◽  
Sio2 Glass ◽  
X Ray ◽  
X Ray Scattering ◽  
Medium Range ◽  
Two Phases ◽  
A Minor

The structure of hydrous amorphous SiO2 is fundamental in order to investigate the effects of water on the physicochemical properties of oxide glasses and magma. The hydrous SiO2 glass with 13 wt.% D2O was synthesized under high-pressure and high-temperature conditions and its structure was investigated by small angle X-ray scattering, X-ray diffraction, and neutron diffraction experiments at pressures of up to 10 GPa and room temperature. This hydrous glass is separated into two phases: a major phase rich in SiO2 and a minor phase rich in D2O molecules distributed as small domains with dimensions of less than 100 Å. Medium-range order of the hydrous glass shrinks compared to the anhydrous SiO2 glass by disruption of SiO4 linkage due to the formation of Si–OD deuterioxyl, while the response of its structure to pressure is almost the same as that of the anhydrous SiO2 glass. Most of D2O molecules are in the small domains and hardly penetrate into the void space in the ring consisting of SiO4 tetrahedra.

scholarly journals Brightest cluster galaxies: the centre can(not?) hold

2020 ◽  
Vol 500 (1) ◽  
pp. 310-318
Author(s):  
Roberto De Propris ◽  
Michael J West ◽  
Felipe Andrade-Santos ◽  
Cinthia Ragone-Figueroa ◽  
Elena Rasia ◽  
...  
Keyword(s):  
Dark Matter ◽  
Local Environment ◽  
Major Axis ◽  
Theoretical Models ◽  
Dark Matter Halo ◽  
Gas Distribution ◽  
X Ray ◽  
Cluster Galaxies ◽  
Peculiar Velocities ◽  
Brightest Cluster Galaxies

ABSTRACT We explore the persistence of the alignment of brightest cluster galaxies (BCGs) with their local environment. We find that a significant fraction of BCGs do not coincide with the centroid of the X-ray gas distribution and/or show peculiar velocities (they are not at rest with respect to the cluster mean). Despite this, we find that BCGs are generally aligned with the cluster mass distribution even when they have significant offsets from the X-ray centre and significant peculiar velocities. The large offsets are not consistent with simple theoretical models. To account for these observations BCGs must undergo mergers preferentially along their major axis, the main infall direction. Such BCGs may be oscillating within the cluster potential after having been displaced by mergers or collisions, or the dark matter halo itself may not yet be relaxed.

scholarly journals The role of AGN activity in the building up of the BCG at z ∼ 1.6

2019 ◽  
Vol 15 (S356) ◽  
pp. 280-284
Author(s):  
Angela Bongiorno ◽  
Andrea Travascio
Keyword(s):  
Galaxy Cluster ◽  
Cluster Galaxy ◽  
X Ray ◽  
Groups Of Galaxies ◽  
Star Forming ◽  
The Core ◽  
The Galaxy ◽  
Multi Wavelength

AbstractXDCPJ0044.0-2033 is one of the most massive galaxy cluster at z ∼1.6, for which a wealth of multi-wavelength photometric and spectroscopic data have been collected during the last years. I have reported on the properties of the galaxy members in the very central region (∼ 70kpc × 70kpc) of the cluster, derived through deep HST photometry, SINFONI and KMOS IFU spectroscopy, together with Chandra X-ray, ALMA and JVLA radio data.In the core of the cluster, we have identified two groups of galaxies (Complex A and Complex B), seven of them confirmed to be cluster members, with signatures of ongoing merging. These galaxies show perturbed morphologies and, three of them show signs of AGN activity. In particular, two of them, located at the center of each complex, have been found to host luminous, obscured and highly accreting AGN (λ = 0.4−0.6) exhibiting broad Hα line. Moreover, a third optically obscured type-2 AGN, has been discovered through BPT diagram in Complex A. The AGN at the center of Complex B is detected in X-ray while the other two, and their companions, are spatially related to radio emission. The three AGN provide one of the closest AGN triple at z > 1 revealed so far with a minimum (maximum) projected distance of 10 kpc (40 kpc). The discovery of multiple AGN activity in a highly star-forming region associated to the crowded core of a galaxy cluster at z ∼ 1.6, suggests that these processes have a key role in shaping the nascent Brightest Cluster Galaxy, observed at the center of local clusters. According to our data, all galaxies in the core of XDCPJ0044.0-2033 could form a BCG of M* ∼ 1012Mȯ hosting a BH of 2 × 108−109Mȯ, in a time scale of the order of 2.5 Gyrs.

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