Charting the Galactic Acceleration Field. I. A Search for Stellar Streams with Gaia DR2 and EDR3 with Follow-up from ESPaDOnS and UVES

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.

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Thousands of Stellar SiO masers in the Galactic center: The Bulge Asymmetries and Dynamic Evolution (BAaDE) survey

Proceedings of the International Astronomical Union ◽

10.1017/s1743921316012394 ◽

2016 ◽

Vol 11 (S322) ◽

pp. 103-106 ◽

Cited By ~ 2

Author(s):

Loránt O. Sjouwerman ◽

Ylva M. Pihlström ◽

R. Michael Rich ◽

Mark R. Morris ◽

Mark J Claussen

Keyword(s):

Velocity Structure ◽

Galactic Center ◽

Galactic Plane ◽

Dynamic Evolution ◽

Stellar Streams ◽

Red Giant ◽

Optical Surveys ◽

Galactic Orbit ◽

Maser Sources

AbstractA radio survey of red giant SiO sources in the inner Galaxy and bulge is not hindered by extinction. Accurate stellar velocities (<1 km/s) are obtained with minimal observing time (<1 min) per source. Detecting over 20,000 SiO maser sources yields data comparable to optical surveys with the additional strength of a much more thorough coverage of the highly obscured inner Galaxy. Modeling of such a large sample would reveal dynamical structures and minority populations; the velocity structure can be compared to kinematic structures seen in molecular gas, complex orbit structure in the bar, or stellar streams resulting from recently infallen systems. Our Bulge Asymmetries and Dynamic Evolution (BAaDE) survey yields bright SiO masers suitable for follow-up Galactic orbit and parallax determination using VLBI.Here we outline our early VLA observations at 43 GHz in the northern bulge and Galactic plane (0<l°<250), and ALMA observations at 86 GHz in the southern bulge (250<l°<360). We report a preliminary overall 70% detection rate in our color-selected MSX sources.

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Search for Stellar Streams in The Galactic Halo From Gaia DR2, GALAH DR2, RAVE DR5 and LAMOST DR4 Data

EPJ Web of Conferences ◽

10.1051/epjconf/202024007012 ◽

2020 ◽

Vol 240 ◽

pp. 07012

Author(s):

Ni Made Kartika Wijayanti ◽

Mochamad Ikbal Arifyanto ◽

Nur Annisa

Keyword(s):

Monte Carlo ◽

Monte Carlo Simulations ◽

Wavelet Transformation ◽

High Probability ◽

Galactic Halo ◽

Tidal Force ◽

3D Kinematics ◽

Halo Stars ◽

Stellar Streams ◽

Gaia Dr2

Stellar streams are stars which are trapped in the same potensial caused by dynamical resonance or tidal force. We aim to analyze kinematic sub- structures (streams) in the Galactic halo by V vs √ U2+ 2V 2 planes of Arifyanto & Fuchs. We crossmatched data from Gaia DR2, GALAH DR2, RAVE DR5 and LAMOST DR4 based on positions. We have 3D kinematics and metallicity data of halo stars selected from kinematics criteria from ratio of probability of thick disk (TD) over halo (H) less than 0.01. Substructures are detected by using wavelet transformation and corrected using 15 Monte Carlo simulations. We obtained four kinematic structures on V vs √U2 + 2V 2 plane which two of them are associated to BB17-1 and BB17-2 streams. All the streams had a high probability from the extragalactic origin.

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Ghostly tributaries to the Milky Way: charting the halo’s stellar streams with the Gaia DR2 catalogue

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/sty2474 ◽

2018 ◽

Vol 481 (3) ◽

pp. 3442-3455 ◽

Cited By ~ 57

Author(s):

Khyati Malhan ◽

Rodrigo A Ibata ◽

Nicolas F Martin

Keyword(s):

Milky Way ◽

Stellar Streams ◽

Gaia Dr2

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Updated parameters of 1743 open clusters based on Gaia DR2

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stab770 ◽

2021 ◽

Vol 504 (1) ◽

pp. 356-371

Author(s):

W S Dias ◽

H Monteiro ◽

A Moitinho ◽

J R D Lépine ◽

G Carraro ◽

...

Keyword(s):

Maximum Likelihood ◽

Open Cluster ◽

Open Clusters ◽

Individual Member ◽

Homogeneous Sample ◽

Membership Probability ◽

Fundamental Parameters ◽

The Mean ◽

Gaia Dr2

ABSTRACT In this study, we follow up our recent paper (Monteiro et al. 2020) and present a homogeneous sample of fundamental parameters of open clusters in our Galaxy, entirely based on Gaia DR2 data. We used published membership probability of the stars derived from Gaia DR2 data and applied our isochrone fitting code, updated as in Monteiro et al. (2020), to GBP and GRPGaia DR2 data for member stars. In doing this, we take into account the nominal errors in the data and derive distance, age, and extinction of each cluster. This work therefore provides parameters for 1743 open clusters and, as a by-product, a list of likely not physical or dubious open clusters is provided as well for future investigations. Furthermore, it was possible to estimate the mean radial velocity of 831 clusters (198 of which are new and unpublished so far), using stellar radial velocities from Gaia DR2 catalogue. By comparing the open cluster distances obtained from isochrone fitting with those obtained from a maximum likelihood estimate of individual member parallaxes, we found a systematic offset of (−0.05 ± 0.04) mas.

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A hyper-runaway white dwarf in Gaia DR2 as a Type Iax supernova primary remnant candidate

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2176 ◽

2019 ◽

Vol 489 (1) ◽

pp. 420-426 ◽

Cited By ~ 2

Author(s):

Nicholas J Ruffini ◽

Andrew R Casey

Keyword(s):

White Dwarf ◽

High Velocity ◽

White Dwarfs ◽

Milky Way ◽

Elemental Abundances ◽

Type Ia ◽

Gaia Dr2 ◽

Rule Out

ABSTRACT Observations of stellar remnants linked to Type Ia and Type Iax supernovae are necessary to fully understand their progenitors. Multiple progenitor scenarios predict a population of kicked donor remnants and partially burnt primary remnants, both moving with relatively high velocity. But only a handful of examples consistent with these two predicted populations have been observed. Here we report the likely first known example of an unbound white dwarf that is consistent with being the fully cooled primary remnant to a Type Iax supernova. The candidate, LP 93-21, is travelling with a galactocentric velocity of $v_{\textrm {gal}} \simeq 605\, {\rm km}\, {\rm s}^{-1}$, and is gravitationally unbound to the Milky Way. We rule out an extragalactic origin. The Type Iax supernova ejection scenario is consistent with its peculiar unbound trajectory, given anomalous elemental abundances are detected in its photosphere via spectroscopic follow-up. This discovery reflects recent models that suggest stellar ejections likely occur often. Unfortunately the intrinsic faintness of white dwarfs, and the uncertainty associated with their direct progenitor systems, makes it difficult to detect and confirm such donors.

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Identifying stellar streams in Gaia DR2 with data mining techniques

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz3479 ◽

2019 ◽

Vol 492 (1) ◽

pp. 1370-1384 ◽

Cited By ~ 5

Author(s):

Nicholas W Borsato ◽

Sarah L Martell ◽

Jeffrey D Simpson

Keyword(s):

Data Mining ◽

Globular Clusters ◽

Dwarf Galaxy ◽

Large Data ◽

Data Sets ◽

Integral Of Motion ◽

Data Mining Techniques ◽

Orbital Parameters ◽

Stellar Streams ◽

Gaia Dr2

ABSTRACT Streams of stars from captured dwarf galaxies and dissolved globular clusters are identifiable through the similarity of their orbital parameters, a fact that remains true long after the streams have dispersed spatially. We calculate the integrals of motion for 31 234 stars, to a distance of 4 kpc from the Sun, which have full and accurate 6D phase space positions in the Gaia DR2 catalogue. We then apply a novel combination of data mining, numerical, and statistical techniques to search for stellar streams. This process returns five high confidence streams (including one which was previously undiscovered), all of which display tight clustering in the integral of motion space. Colour–magnitude diagrams indicate that these streams are relatively simple, old, metal-poor populations. One of these resolved streams shares very similar kinematics and metallicity characteristics with the Gaia-Enceladus dwarf galaxy remnant, but with a slightly younger age. The success of this project demonstrates the usefulness of data mining techniques in exploring large data sets.

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A closer look at the spur, blob, wiggle, and gaps in GD-1

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa917 ◽

2020 ◽

Vol 494 (4) ◽

pp. 5315-5332 ◽

Cited By ~ 1

Author(s):

T J L de Boer ◽

D Erkal ◽

M Gieles

Keyword(s):

Matched Filter ◽

Small Scale ◽

Proper Motions ◽

Stellar Streams ◽

Clear Distance ◽

Filter Approach ◽

To Come ◽

Using Data ◽

Extended View ◽

Gaia Dr2

ABSTRACT The GD-1 stream is one of the longest and coldest stellar streams discovered to date, and one of the best objects for constraining the dark matter properties of the Milky Way. Using data from Gaia DR2, we study the proper motions (PMs), distance, morphology, and density of the stream to uncover small-scale perturbations. The PM cleaned data show a clear distance gradient across the stream, ranging from 7 to 12 kpc. However, unlike earlier studies that found a continuous gradient, we uncover a distance minimum at φ1 ≈ −40 deg, after which the distance increases again. We can reliably trace the stream between −85 < φ1 <15 deg, showing an even further extent to GD-1 beyond the earlier extension of Price-Whelan and Bonaca. We constrain the stream track and density using a Boolean matched filter approach and find three large under densities and significant residuals in the stream track lining up with these gaps. The gaps are located at φ1 = −36, −20, and −3 deg, with the gap at −3 deg being surrounded by a clear sinusoidal wiggle. We argue that this wiggle is due to a perturbation since it has the wrong orientation to come from a progenitor. We compute a total initial stellar mass of the stream segment of 1.58 ± 0.07 × 104 M⊙. With the extended view of the spur in this work, we argue that the spur may be unrelated to the adjacent gap in the stream. Finally, we show that an interaction with the Sagittarius dwarf can create features similar to the spur.

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The hidden giant: discovery of an enormous Galactic dwarf satellite in Gaia DR2

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz1624 ◽

2019 ◽

Vol 488 (2) ◽

pp. 2743-2766 ◽

Cited By ~ 39

Author(s):

G Torrealba ◽

V Belokurov ◽

S E Koposov ◽

T S Li ◽

M G Walker ◽

...

Keyword(s):

Dark Matter ◽

Surface Brightness ◽

Cold Dark Matter ◽

Dwarf Galaxy ◽

Large Magellanic Cloud ◽

Tidal Disruption ◽

Systemic Velocity ◽

Gaia Dr2 ◽

Variability Data

ABSTRACT We report the discovery of a Milky Way satellite in the constellation of Antlia. The Antlia 2 dwarf galaxy is located behind the Galactic disc at a latitude of b ∼ 11° and spans 1.26°, which corresponds to ∼2.9 kpc at its distance of 130 kpc. While similar in spatial extent to the Large Magellanic Cloud, Antlia 2 is orders of magnitude fainter at MV = −9 mag, making it by far the lowest surface brightness system known (at ∼31.9 mag arcsec−2), ∼100 times more diffuse than the so-called ultra diffuse galaxies. The satellite was identified using a combination of astrometry, photometry, and variability data from Gaia Data Release 2, and its nature confirmed with deep archival DECam imaging, which revealed a conspicuous BHB signal. We have also obtained follow-up spectroscopy using AAOmega on the AAT, identifying 159 member stars, and we used them to measure the dwarf’s systemic velocity, 290.9 ± 0.5 km s−1, its velocity dispersion, 5.7 ± 1.1 km s−1, and mean metallicity, [Fe/H] = −1.4. From these properties we conclude that Antlia 2 inhabits one of the least dense dark matter (DM) haloes probed to date. Dynamical modelling and tidal-disruption simulations suggest that a combination of a cored DM profile and strong tidal stripping may explain the observed properties of this satellite. The origin of this core may be consistent with aggressive feedback, or may even require alternatives to cold dark matter (such as ultra-light bosons).

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Gaia GraL: Gaia DR2 gravitational lens systems

Astronomy and Astrophysics ◽

10.1051/0004-6361/201834573 ◽

2019 ◽

Vol 628 ◽

pp. A17 ◽

Cited By ~ 1

Author(s):

O. Wertz ◽

D. Stern ◽

A. Krone-Martins ◽

L. Delchambre ◽

C. Ducourant ◽

...

Keyword(s):

Time Delay ◽

Mass Density ◽

Position Angle ◽

Gravitational Lens ◽

Density Profiles ◽

Data Release ◽

The Impact ◽

Gaia Dr2 ◽

Different Levels

We report the spectroscopic confirmation and modeling of the quadruply imaged quasar GRAL 113100–441959, the first gravitational lens (GL) to be discovered from a machine learning technique that only relies on the relative positions and fluxes of the observed images without considering colour informations. Follow-up spectra obtained with Keck/LRIS reveal the lensing nature of this quadruply imaged quasar with redshift zs = 1.090 ± 0.002, but show no evidence of the central lens galaxy. Using the image positions and G-band flux ratios provided by Gaia Data Release 2 as constraints, we modeled the system with a singular power-law elliptical mass distribution (SPEMD) plus external shear, to different levels of complexity. We show that relaxing the isothermal constraint of the SPEMD does not lead to statistically significant different results in terms of fitting the lensing data. We thus simplified the SPEMD to a singular isothermal ellipsoid to estimate the Einstein radius of the main lens galaxy θE = 0.″851, the intensity and position angle of the external shear (γ,θγ) = (0.044, 11.°5), and we predict the lensing galaxy position to be (θgal,1, θgal,2) = (−0.″424, −0.″744) with respect to image A. We provide time delay predictions for pairs of images, assuming a plausible range of lens redshift values zl between 0.5 and 0.9. Finally, we examine the impact on time delays of the so-called source position transformation, a family of degeneracies existing between different mass density profiles that reproduce most of the lensing observables equally well. We show that this effect contributes significantly to the time delay error budget and cannot be ignored during the modeling. This has implications for robust cosmography applications of lensed systems. GRAL 113100–441959 is the first in a series of seven new spectroscopically confirmed GLs discovered from Gaia Data Release 2.

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