Preparing to Discover the Unknown with Rubin LSST: Time Domain

Abstract Perhaps the most exciting promise of the Rubin Observatory Legacy Survey of Space and Time (LSST) is its capability to discover phenomena never before seen or predicted: true astrophysical novelties; but the ability of LSST to make these discoveries will depend on the survey strategy. Evaluating candidate strategies for true novelties is a challenge both practically and conceptually. Unlike traditional astrophysical tracers like supernovae or exoplanets, for anomalous objects, the template signal is by definition unknown. We approach this problem by assessing survey completeness in a phase space defined by object color and flux (and their evolution), and considering the volume explored by integrating metrics within this space with the observation depth, survey footprint, and stellar density. With these metrics, we explore recent simulations of the Rubin LSST observing strategy across the entire observed spatial footprint and in specific Local Volume regions: the Galactic Plane and Magellanic Clouds. Under our metrics, observing strategies with greater diversity of exposures and time gaps tend to be more sensitive to genuinely new transients, particularly over time-gap ranges left relatively unexplored by previous surveys. To assist the community, we have made all of the tools developed publicly available. While here we focus on transients, an extension of the scheme to include proper motions and the detection of associations or populations of interest will be communicated in Paper II of this series. This paper was written with the support of the Vera C. Rubin LSST Transients and Variable Stars and Stars, Milky Way, Local Volume Science Collaborations.

Download Full-text

25 Years of the Southern Skies Monitoring by OGLE

Proceedings of the International Astronomical Union ◽

10.1017/s174392131800265x ◽

2017 ◽

Vol 14 (S339) ◽

pp. 226-229 ◽

Cited By ~ 1

Author(s):

Ł. Wyrzykowski ◽

P. Pietrukowicz ◽

Keyword(s):

Time Domain ◽

Gravitational Lensing ◽

Milky Way ◽

Extrasolar Planets ◽

Variable Stars ◽

Matter Content ◽

Magellanic Clouds ◽

Photometric Data ◽

Galactic Bulge ◽

Selection Of

AbstractThe Optical Gravitational Lensing Experiment (OGLE) started at Las Campanas Observatory in 1992 with a pilot monitoring programme of two million stars in the Galactic Bulge. It is still operating today, collecting time-domain photometric data of a billion stars from the densest regions in the southern sky. Among its main achievements are discoveries of thousands of microlensing events, a few dozen extrasolar planets and candidates for black holes, a million variable stars, and thousands of quasars and supernovæ. It has made a major contribution to the studies of the dark-matter content of the Milky Way halo, the structure of the Galactic Bulge, the Magellanic Clouds, and new classes of variable stars. In this its 25th anniversary year, we presented a selection of the major scientific highlights of OGLE.

Download Full-text

The VMC survey

Astronomy and Astrophysics ◽

10.1051/0004-6361/202037478 ◽

2020 ◽

Vol 641 ◽

pp. A134

Author(s):

Thomas Schmidt ◽

Maria-Rosa L. Cioni ◽

Florian Niederhofer ◽

Kenji Bekki ◽

Cameron P. M. Bell ◽

...

Keyword(s):

Proper Motion ◽

Milky Way ◽

Dwarf Galaxies ◽

Dynamical Evolution ◽

Large Magellanic Cloud ◽

Small Population ◽

Magellanic Cloud ◽

Magellanic Clouds ◽

Proper Motions ◽

Flow Motion

Context. The Magellanic Clouds are a nearby pair of interacting dwarf galaxies and satellites of the Milky Way. Studying their kinematic properties is essential to understanding their origin and dynamical evolution. They have prominent tidal features and the kinematics of these features can give hints about the formation of tidal dwarfs, galaxy merging and the stripping of gas. In addition they are an example of dwarf galaxies that are in the process of merging with a massive galaxy. Aims. The goal of this study is to investigate the kinematics of the Magellanic Bridge, a tidal feature connecting the Magellanic Clouds, using stellar proper motions to understand their most recent interaction. Methods. We calculated proper motions based on multi-epoch Ks-band aperture photometry, which were obtained with the Visible and Infrared Survey Telescope for Astronomy (VISTA), spanning a time of 1−3 yr, and we compared them with Gaia Data Release 2 (DR2) proper motions. We tested two methods for removing Milky Way foreground stars using Gaia DR2 parallaxes in combination with VISTA photometry or using distances based on Bayesian inference. Results. We obtained proper motions for a total of 576 411 unique sources over an area of 23 deg2 covering the Magellanic Bridge including mainly Milky Way foreground stars, background galaxies, and a small population of possible Magellanic Bridge stars (< 15 000), which mostly consist of giant stars with 11.0 < Ks < 19.5 mag. The first proper motion measurement of the Magellanic Bridge centre is 1.80 ± 0.25 mas yr−1 in right ascension and −0.72 ± 0.13 mas yr−1 in declination. The proper motion measurements of stars along the Magellanic Bridge from the VISTA survey of the Magellanic Cloud system (VMC) and Gaia DR2 data confirm a flow motion from the Small to the Large Magellanic Cloud. This flow can now be measured all across the entire length of the Magellanic Bridge. Conclusions. Our measurements indicate that the Magellanic Bridge is stretching. By converting the proper motions to tangential velocities, we obtain ∼110 km s−1 in the plane of the sky. Therefore it would take a star roughly 177 Myr to cross the Magellanic Bridge.

Download Full-text

New analysis of the proper motions of the Magellanic Clouds using HST/WFPC2

Proceedings of the International Astronomical Union ◽

10.1017/s1743921308028305 ◽

2008 ◽

Vol 4 (S256) ◽

pp. 93-98 ◽

Cited By ~ 1

Author(s):

Nitya Kallivayalil ◽

Roeland P. van der Marel ◽

Jay Anderson ◽

Gurtina Besla ◽

Charles Alcock

Keyword(s):

Relative Velocity ◽

Milky Way ◽

Three Dimensional ◽

Magellanic Clouds ◽

Dark Halo ◽

Escape Velocity ◽

Proper Motions ◽

First Passage ◽

Good Consistency ◽

Better Than

AbstractIn HST Cycles 11 and 13 we obtained two epochs of ACS/HRC data for fields in the Magellanic Clouds centered on background quasars. We used these data to determine the proper motions of the LMC and SMC to better than 5% and 15% respectively. The results had a number of unexpected implications for the Milky Way-LMC-SMC system. The implied three-dimensional velocities were larger than previously believed and close to the escape velocity in a standard 1012 M⊙ Milky Way dark halo, implying that the Clouds may be on their first passage. Also, the relative velocity between the LMC and SMC was larger than expected, leaving open the possibility that the Clouds may not be bound to each other. To further verify and refine our results we requested an additional epoch of data in Cycle 16 which is being executed with WFPC2/PC due to the failure of ACS. We present the results of an ongoing analysis of these WFPC2 data which indicate good consistency with the two-epoch results.

Download Full-text

The SRC Near-Infrared Survey of the Galactic Plane

Publications of the Astronomical Society of Australia ◽

10.1017/s1323358000016532 ◽

1981 ◽

Vol 4 (2) ◽

pp. 251-254 ◽

Cited By ~ 12

Author(s):

M. Hartley ◽

J. A. Dawe

Keyword(s):

Near Infrared ◽

Milky Way ◽

Galactic Plane ◽

Magellanic Clouds ◽

Schmidt Telescope ◽

Photographic Paper ◽

Infrared Survey

In 1975, Hoessel, Elias, Wade and Huchra commenced a near infrared survey of 80 fields in the northern Milky Way with the Palomar 1.2 m Schmidt telescope, (Hoessel et al. 1979). This has now been issued as an atlas reproduced in the form of photographic paper prints. In 1977, the SRC 1.2 m Schmidt telescope at Siding Spring was authorized to commence a complementary survey of the southern Milky Way, consisting of the 151 ESO/SRC survey fields which have centres within 10° of the galactic plane and negative declinations (see Fig. 1). A further 12 fields have subsequently been added to the survey to permit coverage of the Large and Small Magellanic Clouds.

Download Full-text

Evolution of abundance gradients for galactic plane PNe

Proceedings of the International Astronomical Union ◽

10.1017/s1743921310011701 ◽

2009 ◽

Vol 5 (H15) ◽

pp. 792-792

Author(s):

A.F. Kholtygin ◽

Yu.V. Milanova ◽

V.V. Akimkin

Keyword(s):

Milky Way ◽

Galactic Plane ◽

Planetary Nebulae ◽

Thin Disk ◽

Magellanic Clouds ◽

Element Abundances

AbstractThe modern observations of planetary nebulae (PNe) are used to recalculate the element abundances for more than 150 PNe of the Milky Way and Magellanic Clouds. Basing on our data, we study the evolution of the abundance gradients for PNe in the thin disk and in the bulge.

Download Full-text

Workshop Reports

Proceedings of the International Astronomical Union ◽

10.1017/s1743921318002612 ◽

2017 ◽

Vol 14 (S339) ◽

pp. 205-205

Keyword(s):

Machine Learning ◽

Time Domain ◽

Milky Way ◽

Magellanic Clouds ◽

Unique Challenge ◽

X Ray ◽

New Instrumentation ◽

Radio Transients

Abstract14 Workshops were held during the Symposium, and all but one submitted a report of the discussions that took place. The reports are arranged in the following order:1. Radio Transients in the Era of Multi-Messenger Astrophysics………. 2072. Stellar Variability: From Citizen Science to Citizen Astronomy………. 2153. Getting Ready for TESS: an On-Hand Software Tutorial………. 2204. 25 Years of the Southern Skies Monitoring by OGLE………. 2265. A-Type Stars as a Unique Challenge in Time-Domain Studies………. 2306. X-ray Binary Transients in the Magellanic Clouds and the Milky Way………. 2367. Towards Science with LSST: Data Products and Communications………. 2418. Supernovæ………. 2459. Exploring Data Sonification to Enable, Enhance, and Accelerate the Analysis of Big, Noisy, and Multi-Dimensional Data ………. 25110. New Instrumentation for Transient Follow-Up ………. 25711. Nuclear Transients ………. 26312. Accessing Data for Long-Term Variability ………. 26913. Machine Learning for Transient Classification ………. 27414. Calibration and Standardisation ………. 275

Download Full-text

Disk stars in the Milky Way detected beyond 25 kpc from its center

Astronomy and Astrophysics ◽

10.1051/0004-6361/201832880 ◽

2018 ◽

Vol 612 ◽

pp. L8 ◽

Cited By ~ 7

Author(s):

M. López-Corredoira ◽

C. Allende Prieto ◽

F. Garzón ◽

H. Wang ◽

C. Liu ◽

...

Keyword(s):

Milky Way ◽

Galactic Plane ◽

Maximum Size ◽

Maximum Distance ◽

Stellar Disk ◽

Stellar Density ◽

Metallicity Distribution

Context. The maximum size of the Galactic stellar disk is not yet known. Some studies have suggested an abrupt drop-off of the stellar density of the disk at Galactocentric distances R ≳ 15 kpc, which means that in practice no disk stars or only very few of them should be found beyond this limit. However, stars in the Milky Way plane are detected at larger distances. In addition to the halo component, star counts have placed the end of the disk beyond 20 kpc, although this has not been spectroscopically confirmed so far. Aims. Here, we aim to spectroscopically confirm the presence of the disk stars up to much larger distances. Methods. With data from the LAMOST and SDSS-APOGEE spectroscopic surveys, we statistically derived the maximum distance at which the metallicity distribution of stars in the Galactic plane is distinct from that of the halo populations. Results. Our analysis reveals the presence of disk stars at R > 26 kpc (99.7% C.L.) and even at R > 31 kpc (95.4% C.L.).

Download Full-text

VVVX-Gaia discovery of a low luminosity globular cluster in the Milky Way disk

Astronomy and Astrophysics ◽

10.1051/0004-6361/202039233 ◽

2020 ◽

Vol 642 ◽

pp. L19

Author(s):

E. R. Garro ◽

D. Minniti ◽

M. Gómez ◽

J. Alonso-García ◽

R. H. Barbá ◽

...

Keyword(s):

Globular Clusters ◽

Near Infrared ◽

Milky Way ◽

Galactic Plane ◽

Galactic Disk ◽

Ring Structure ◽

Galactic Centre ◽

Distance Modulus ◽

Proper Motions ◽

Optical Photometry

Context. Milky Way globular clusters (GCs) are difficult to identify at low Galactic latitudes because of high differential extinction and heavy star crowding. The new deep near-infrared (IR) images and photometry from the VISTA Variables in the Via Láctea Extended Survey (VVVX) allow us to chart previously unexplored regions. Aims. Our long term aim is to complete the census of Milky Way GCs. The immediate goals are to estimate the astrophysical parameters for the newly discovered GC candidates, measuring their reddenings, extinctions, distances, total luminosities, proper motions, sizes, metallicities, and ages. Methods. We used the near-IR VVVX survey database, in combination with the optical photometry and proper motions (PMs) from Gaia Data Release 2 (DR2), and with the Two Micron All Sky Survey photometry to search for and characterise new GCs within the southern Galactic plane (|b| < 5°). Results. We report the detection of a heretofore unknown Galactic GC at RA = 14:09:00.0; Dec = −65:37:12 (J2000) corresponding to l = 310.828 deg; and b = −3.944 deg in galactic coordinates. We calculate a reddening of E(J − Ks) = (0.3 ± 0.03) mag and an extinction of AKs = (0.15 ± 0.01) mag for this new GC. Its distance modulus and corresponding distance were measured as (m − M) = (15.93 ± 0.03) mag and D = (15.5 ± 1.0) kpc, respectively. We also estimate the metallicity and age by comparison with known GCs and by fitting PARSEC and Dartmouth isochrones, finding [Fe/H] = ( − 0.70 ± 0.2) dex and t = (11.0 ± 1.0) Gyr. The mean GC PMs from Gaia DR2 are μα* = ( − 4.68 ± 0.47) mas yr−1 and μδ = ( − 1.34 ± 0.45) mas yr−1. The total luminosity of our cluster is estimated to be MKs = ( − 7.76 ± 0.5) mag. The core and tidal radii from the radial density profile are rc ∼ 2.1′ (4.6 pc) and rt = 6.5′ (14.6 pc) at the cluster distance. Conclusions. We have found a new low luminosity, old and metal-rich GC, situated in the far side of the Galactic disk at RG = 11.2 kpc from the Galactic centre and at z = 1.0 kpc below the plane. Interestingly, the location, metallicity, and age of this GC are coincident with the Monoceros ring structure.

Download Full-text

Galactic orbits of stars

Symposium - International Astronomical Union ◽

10.1017/s0074180900105340 ◽

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.

Download Full-text

Remarkable Symmetries in the Milky Way Disc's Magnetic Field

Publications of the Astronomical Society of Australia ◽

10.1071/as10045 ◽

2011 ◽

Vol 28 (2) ◽

pp. 171-176 ◽

Cited By ~ 15

Author(s):

P. P. Kronberg ◽

K. J. Newton-McGee

Keyword(s):

Magnetic Structure ◽

Large Scale ◽

Milky Way ◽

Galactic Center ◽

Galactic Plane ◽

Galactic Disk ◽

Field Structure ◽

Field Pattern ◽

Close Coupling ◽

Sign Change

AbstractWe apply a new, expanded compilation of extragalactic source Faraday rotation measures (RM) to investigate the broad underlying magnetic structure of the Galactic disk at latitudes ∣b∣ ≲15° over all longitudes l, where our total number of RMs is comparable to those in the combined Canadian Galactic Plane Survey (CGPS) at ∣b∣ < 4° and the Southern Galactic Plane (SGPS) ∣b∣<1.5°. We report newly revealed, remarkably coherent patterns of RM at ∣b∣≲15° from l∼270° to ∼90° and RM(l) features of unprecedented clarity that replicate in l with opposite sign on opposite sides of the Galactic center. They confirm a highly patterned bisymmetric field structure toward the inner disc, an axisymmetic pattern toward the outer disc, and a very close coupling between the CGPS/SGPS RMs at ∣b∣≲3° (‘mid-plane’) and our new RMs up to ∣b∣∼15° (‘near-plane’). Our analysis also shows the vertical height of the coherent component of the disc field above the Galactic disc's mid-plane—to be ∼1.5 kpc out to ∼6 kpc from the Sun. This identifies the approximate height of a transition layer to the halo field structure. We find no RM sign change across the plane within ∣b∣∼15° in any longitude range. The prevailing disc field pattern and its striking degree of large-scale ordering confirm that our side of the Milky Way has a very organized underlying magnetic structure, for which the inward spiral pitch angle is 5.5°±1° at all ∣b∣ up to ∼12° in the inner semicircle of Galactic longitudes. It decreases to ∼0° toward the anticentre.

Download Full-text