scholarly journals An extended Pal 5 stream in Gaia DR2

2020 ◽  
Vol 493 (4) ◽  
pp. 4978-4986 ◽  
Author(s):  
Nathaniel Starkman ◽  
Jo Bovy ◽  
Jeremy J Webb
Keyword(s):  
Constant Width ◽  
Host Galaxy ◽  
Tidal Tail ◽  
Galactic Potential ◽  
Excellent Candidate ◽  
Detailed Search ◽  
Tidal Tails ◽  
Gaia Dr2 ◽  
Sensitive Method

ABSTRACT We present the results of a detailed search for members of the Pal 5 tidal tail system in Gaia Data Release 2 (DR2). Tidal tails provide a sensitive method for measuring the current and past gravitational potential of their host galaxy as well as for testing predictions for the abundance of dark matter subhaloes. The Pal 5 globular cluster and its associated tails are an excellent candidate for such analysis; however, only ∼23° of arc are currently known, with in particular the leading tail much shorter than the trailing. Using Gaia DR2 and its precise astrometry, we extend the known extent of the Pal 5 tail to ∼30°, 7° of which are newly detected along the leading arm. The detected leading and trailing arms are symmetric in length and remain near constant width. This detection constrains proposed models in which the Galactic bar truncates Pal 5’s leading arm. Follow-up spectroscopic observations are necessary to verify the candidate stream stars are consistent with the known tidal tails. If confirmed, this Pal 5 stream extension opens up new possibilities to constrain the Galactic potential.

scholarly journals Constraints on the circumburst environments of short gamma-ray bursts

2020 ◽  
Vol 495 (4) ◽  
pp. 4782-4799 ◽  
Author(s):  
Brendan O’Connor ◽  
Paz Beniamini ◽  
Chryssa Kouveliotou
Keyword(s):  
Gamma Ray ◽  
Galactic Halo ◽  
Gamma Ray Bursts ◽  
Light Curves ◽  
Host Galaxy ◽  
Host Galaxies ◽  
Binary Neutron Star ◽  
Range Of Values ◽  
Short Grbs

ABSTRACT Observational follow up of well localized short gamma-ray bursts (SGRBs) has left $20\!-\!30{{\ \rm per\ cent}}$ of the population without a coincident host galaxy association to deep optical and NIR limits (≳26 mag). These SGRBs have been classified as observationally hostless due to their lack of strong host associations. It has been argued that these hostless SGRBs could be an indication of the large distances traversed by the binary neutron star system (due to natal kicks) between its formation and its merger (leading to an SGRB). The distances of GRBs from their host galaxies can be indirectly probed by the surrounding circumburst densities. We show that a lower limit on those densities can be obtained from early afterglow light curves. We find that ${\lesssim}16{{\ \rm per\ cent}}$ of short GRBs in our sample took place at densities ≲10−4 cm−3. These densities represent the expected range of values at distances greater than the host galaxy’s virial radii. We find that out of the five SGRBs in our sample that have been found to be observationally hostless, none are consistent with having occurred beyond the virial radius of their birth galaxies. This implies one of two scenarios. Either these observationally hostless SGRBs occurred outside of the half-light radius of their host galaxy, but well within the galactic halo, or in host galaxies at moderate to high redshifts (z ≳ 2) that were missed by follow-up observations.

scholarly journals An ASKAP survey for H i absorption towards dust-obscured quasars

2019 ◽  
Vol 489 (4) ◽  
pp. 4926-4943 ◽  
Author(s):  
M Glowacki ◽  
J R Allison ◽  
V A Moss ◽  
E K Mahony ◽  
E M Sadler ◽  
...  
Keyword(s):  
Galaxy Evolution ◽  
Spectral Energy Distribution ◽  
Galactic Nuclei ◽  
Host Galaxy ◽  
Spectral Energy ◽  
Neutral Medium ◽  
Host Galaxies ◽  
Gas Kinematics ◽  
Neutral Gas

ABSTRACT Obscuration of quasars by accreted gas and dust, or dusty intervening galaxies, can cause active galactic nuclei (AGN) to be missed in optically selected surveys. Radio observations can overcome this dust bias. In particular, radio surveys searching for H i absorption inform us on how the AGN can impact on the cold neutral gas medium within the host galaxy, or the population of intervening galaxies through the observed line of sight gas kinematics. We present the results of an H i absorption line survey at 0.4 < z < 1 towards 34 obscured quasars with the Australian SKA Pathfinder (ASKAP) commissioning array. We detect three H i absorption lines, with one of these systems previously unknown. Through optical follow-up for two sources, we find that in all detections the H i gas is associated with the AGN, and hence that these AGN are obscured by material within their host galaxies. Most of our sample are compact, and in addition, are either gigahertz peaked spectrum (GPS), or steep spectrum (CSS) sources, both thought to represent young or recently re-triggered radio AGN. The radio spectral energy distribution classifications for our sample agree with galaxy evolution models in which the obscured AGN has only recently become active. Our associated H i detection rate for GPS and compact SS sources matches those of other surveys towards such sources. We also find shallow and asymmetric H i absorption features, which agrees with previous findings that the cold neutral medium in compact radio galaxies is typically kinematically disturbed by the AGN.

scholarly journals 1411+442: Optical Imaging of a BAL QSO

1987 ◽  
Vol 121 ◽  
pp. 395-397
Author(s):  
J.B. Hutchings
Keyword(s):  
Optical Imaging ◽  
Spiral Galaxy ◽  
Host Galaxy ◽  
Tidal Tail

Results are presented of optical imaging of the low redshift BAL QSO 1411+442, in four colours. The host galaxy is revealed as an inclined spiral galaxy with a long arm which may be a tidal tail. There also appears to be connecting luminosity to two nearby objects. There is a straight blue feature emerging from the nucleus and Ha emission from an oppositely directed filament. [O III] appears to be enhanced in some outer regions. While the host galaxy is more exotic than usual for QSOs, it is not obvious how these properties are connected with the BAL phenomenon.

scholarly journals Tidal tails of open star clusters as probes of early gas expulsion

2020 ◽  
Vol 640 ◽  
pp. A84 ◽  
Author(s):  
František Dinnbier ◽  
Pavel Kroupa
Keyword(s):  
Numerical Simulations ◽  
Analytical Model ◽  
Initial Conditions ◽  
Star Clusters ◽  
Open Star Clusters ◽  
Orbital Parameters ◽  
Open Star ◽  
Tidal Tail ◽  
Velocity Dispersions ◽  
Tidal Tails

Context. Star clusters form in the densest parts of infrared dark clouds. The emergence of massive stars expels the residual gas that has not formed stars yet. Gas expulsion lowers the gravitational potential of the embedded cluster, unbinding many of the cluster stars. These stars then move on their own trajectories in the external gravitational field of the Galaxy, forming a tidal tail. Aims. We investigate, for the first time, the formation and evolution of a tidal tail that forms due to expulsion of primordial gas. We contrast the morphology and kinematics of this tail with that of another tidal tail that forms by gradual dynamical evaporation of the star cluster. We intend to provide predictions that can determine the dynamical origin of possibly observed tidal tails around dynamically evolved (age  ≳  100 Myr) galactic star clusters by the Gaia mission. These observations might estimate the fraction of the initial cluster population that gets released in the gas expulsion event. The severity of the initial gas expulsion is given by the star formation efficiency and the timescale of gas expulsion for the cluster when it was still embedded in its natal gas. A study with a more extended parameter space of the initial conditions is performed in the follow up paper. Methods. We provide a semi-analytical model for the tail evolution. The model is compared against direct numerical simulations using NBODY6. Results. Tidal tails released during gas expulsion have different kinematic properties than the tails gradually forming due to evaporation; the latter kind have been extensively studied. The gas expulsion tidal tail shows non-monotonic expansion with time, where longer epochs of expansion are interspersed with shorter epochs of contraction. The tail thickness and velocity dispersions vary strongly, but not exactly periodically, with time. The times of minima of tail thickness and velocity dispersions are given only by the properties of the galactic potential, and not by the properties of the cluster. The estimates provided by the (semi-)analytical model for the extent of the tail, the minima of tail thickness, and velocity dispersions are in a very good agreement with the NBODY6 simulations. This implies that the semi-analytic model can be used to estimate the properties of the gas expulsion tidal tail for a cluster of a given age and orbital parameters without the necessity of performing numerical simulations.

Investigation of the nearby open clusters with Gaia DR2 data

2019 ◽  
Vol 14 (S351) ◽  
pp. 502-506
Author(s):  
Anton F. Seleznev ◽  
Vladimir M. Danilov ◽  
Giovanni Carraro
Keyword(s):  
Three Dimensional ◽  
Open Clusters ◽  
Dimensional Structure ◽  
Proper Motions ◽  
Membership Probability ◽  
First Results ◽  
Alpha Persei ◽  
Mass Functions ◽  
Tidal Tails ◽  
Gaia Dr2

AbstractGaia DR2 catalog provides a unique possibility to study the three-dimensional structure and the three-dimensional velocity field of the nearby open clusters. We can either select stars with a maximum membership probability and the most accurate values for the proper motions, parallaxes, and the radial velocities, or study these clusters statistically using overwhelmingly large areas of sky of tens by tens degrees. The second approach allows us to reveal the extensive outer parts of the clusters - a corona and the tidal tails and to study the luminosity and mass functions of these clusters. We present the first results of the investigation of several nearby open clusters, including Pleiades, Alpha Persei, Ruprecht 147.

scholarly journals Hα Kinematics of Tidal Tails in Interacting Systems: Projection Effects and Dark Matter in TDGs

2004 ◽  
Vol 217 ◽  
pp. 526-531
Author(s):  
Philippe Amram ◽  
Fréderic Bournaud ◽  
Pierre-Alain Duc
Keyword(s):  
Dark Matter ◽  
Dwarf Galaxies ◽  
Matter Content ◽  
Field Of View ◽  
Large Field ◽  
Ionized Gas ◽  
Tidal Tail ◽  
Fabry Perot ◽  
Interacting Systems ◽  
Tidal Tails

Several interacting systems exhibit at the tip of their long tidal tails massive condensations of atomic hydrogen, which may be the progenitors of Tidal Dwarf Galaxies. Because, quite often, these tails are observed edge-on, projection effects have been claimed to account for the large HI column densities measured there. Here we show that determining the velocity field all along the tidal features, one may disentangle projection effects along the line of view from real bound structures. Due to its large field of view, high spectral and 2D spatial resolutions, Fabry-Perot observations of the ionized gas are well adapted to detect a kinematical signature of either streaming motions along a bent tidal tail or of in-falling/rotating material associated with a forming TDG. Spectroscopic observations also allow to measure the dynamical masses of the TDGs that are already relaxed and check their dark matter content.

scholarly journals GRB 171205A/SN 2017iuk: A local low-luminosity gamma-ray burst

2018 ◽  
Vol 619 ◽  
pp. A66 ◽  
Author(s):  
V. D’Elia ◽  
S. Campana ◽  
A. D’Aì ◽  
M. De Pasquale ◽  
S. W. K. Emery ◽  
...  
Keyword(s):  
Gamma Ray ◽  
High Energy ◽  
Host Galaxy ◽  
Isotropic Energy ◽  
Optical Telescope ◽  
X Ray ◽  
Hydrogen Column Density ◽  
Peak Energy ◽  
First Time

Context. Gamma-ray bursts (GRBs) occurring in the local Universe constitute an interesting sub-class of the GRB family, since their luminosity is on average lower than that of their cosmological analogs. Attempts to understand in a global way this peculiar behaviour is still not possible, since the sample of low redshift GRBs is small, and the properties of individual objects are too different from each other. In addition, their closeness (and consequently high fluxes) make these sources ideal targets for extensive follow-up even with small telescopes, considering also that these GRBs are conclusively associated with supernova (SN) explosions. Aims. We aim to contribute to the study of local bursts by reporting the case of GRB 171205A. This source was discovered by Swift Burst Alert Telescope (BAT) on 2017, December 5 and soon associated with a low redshift host galaxy (z = 0.037), and an emerging SN (SN 2017iuk). Methods. We analyzed the full Swift dataset, comprising the UV-Optical Telescope (UVOT), X-ray Telescope (XRT) and BAT data. In addition, we employed the Konus-Wind high energy data as a valuable extension at γ-ray energies. Results. The photometric SN signature is clearly visible in the UVOT u, b and ν filters. The maximum emission is reached at ∼13 (rest frame) days, and the whole bump resembles that of SN 2006aj, but lower in magnitude and with a shift in time of +2 d. A prebump in the ν-band is also clearly visible, and this is the first time that such a feature is not observed achromatically in GRB–SNe. Its physical origin cannot be easily explained. The X-ray spectrum shows an intrinsic Hydrogen column density NH,int = 7.4+4.1−3.6 × 1020 cm−2, which is at the low end of the N H, int, even considering just low redshift GRBs. The spectrum also features a thermal component, which is quite common in GRBs associated with SNe, but whose origin is still a matter of debate. Finally, the isotropic energy in the γ-ray band, Eiso = 2.18+0.63−5.0 × 1049 erg, is lower than those of cosmological GRBs. Combining this value with the peak energy in the same band, Ep = 125+141−37 keV, implies that GRB 171205A is an outlier of the Amati relation, as are some other low redshift GRBs, and its emission mechanism should be different from that of canonical, farther away GRBs.

scholarly journals Rediscovering the tidal tails of NGC 288 with Gaia DR2

2019 ◽  
Vol 484 (1) ◽  
pp. L114-L118 ◽  
Author(s):  
Shaziana Kaderali ◽  
Jason A S Hunt ◽  
Jeremy J Webb ◽  
Natalie Price-Jones ◽  
Raymond Carlberg
Keyword(s):  
Tidal Tails ◽  
Gaia Dr2

scholarly journals The Gravity Collective: A Search for the Electromagnetic Counterpart to the Neutron Star–Black Hole Merger GW190814

2021 ◽  
Vol 923 (2) ◽  
pp. 258
Author(s):  
Charles D. Kilpatrick ◽  
David A. Coulter ◽  
Iair Arcavi ◽  
Thomas G. Brink ◽  
Georgios Dimitriadis ◽  
...  
Keyword(s):  
Black Hole ◽  
Neutron Star ◽  
Gamma Ray ◽  
Absolute Magnitude ◽  
Host Galaxy ◽  
Opening Angle ◽  
Gamma Ray Burst ◽  
Localization Region ◽  
Rule Out

Abstract We present optical follow-up imaging obtained with the Katzman Automatic Imaging Telescope, Las Cumbres Observatory Global Telescope Network, Nickel Telescope, Swope Telescope, and Thacher Telescope of the LIGO/Virgo gravitational wave (GW) signal from the neutron star–black hole (NSBH) merger GW190814. We searched the GW190814 localization region (19 deg2 for the 90th percentile best localization), covering a total of 51 deg2 and 94.6% of the two-dimensional localization region. Analyzing the properties of 189 transients that we consider as candidate counterparts to the NSBH merger, including their localizations, discovery times from merger, optical spectra, likely host galaxy redshifts, and photometric evolution, we conclude that none of these objects are likely to be associated with GW190814. Based on this finding, we consider the likely optical properties of an electromagnetic counterpart to GW190814, including possible kilonovae and short gamma-ray burst afterglows. Using the joint limits from our follow-up imaging, we conclude that a counterpart with an r-band decline rate of 0.68 mag day−1, similar to the kilonova AT 2017gfo, could peak at an absolute magnitude of at most −17.8 mag (50% confidence). Our data are not constraining for “red” kilonovae and rule out “blue” kilonovae with M > 0.5 M ⊙ (30% confidence). We strongly rule out all known types of short gamma-ray burst afterglows with viewing angles <17° assuming an initial jet opening angle of ∼5.°2 and explosion energies and circumburst densities similar to afterglows explored in the literature. Finally, we explore the possibility that GW190814 merged in the disk of an active galactic nucleus, of which we find four in the localization region, but we do not find any candidate counterparts among these sources.

The features of the course of the disease in patients with primary metastatic lymph nodes of the neck

2016 ◽  
Vol 21 (4) ◽  
pp. 195-197
Author(s):  
E. P Kulikov ◽  
Tatyana V. Zakharkina ◽  
M. E Ryazantsev ◽  
M. B Zaytsev ◽  
E. L Sashina
Keyword(s):  
Lymph Nodes ◽  
Clinical Picture ◽  
Careful Examination ◽  
Metastatic Lymph Nodes ◽  
Metastatic Lymph ◽  
Detailed Search ◽  
Initial Focus ◽  
Clinical Cases

In this report there are presented two clinical cases, describing the heterogeneity of the course of the disease in patients with primary metastatic lymph nodes of the neck. The clinical picture of these patients was shown to be atypical and requires not only a detailed search of initial focus at the first visit of the patient, but also a more careful examination in the course of future follow-up observation.

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