Finding evolved stars in the inner Galactic disk with Gaia

The Bulge Asymmetries and Dynamical Evolution (BAaDE) survey will provide positions and line-of-sight velocities of ~20,000 evolved, maser bearing stars in the Galactic plane. Although this Galactic region is affected by optical extinction, BAaDE targets may have Gaia cross-matches, eventually providing additional stellar information. In an initial attempt to cross-match BAaDE targets with Gaia, we have found more than 5,000 candidates. Of these, we may expect half to show SiO emission, which will allow us to obtain velocity information. The cross-match is being refined to avoid false positives using different criteria based on distance analysis, flux variability, and color assessment in the mid- and near-IR. Once the cross-matches can be confirmed, we will have a unique sample to characterize the stellar population of evolved stars in the Galactic bulge, which can be considered fossils of the Milky Way formation.Comment: To appear in the Proceedings of the IAU Symposium No. 330: "Astrometry and Astrophysics in the Gaia sky

COLA. III. Radio Detection of Active Galactic Nucleus in Compact Moderate Luminosity Infrared Galaxies

We present results from 4.8 GHz Very Large Array (VLA) and global very long baseline interferometry (VLBI) observations of the northern half of the moderate FIR luminosity (median L_(IR) = 10^(11.01) L_☉) COLA sample of star-forming galaxies. VLBI sources are detected in a high fraction (20/90) of the galaxies observed. The radio luminosities of these cores (~10^(21) W Hz^(–1)) are too large to be explained by radio supernovae or supernova remnants and we argue that they are instead powered by active galactic nuclei (AGNs). These sub-parsec scale radio cores are preferentially detected toward galaxies whose VLA maps show bright 100-500 parsec scale nuclear radio components. Since these latter structures tightly follow the FIR to radio-continuum correlation for star formation, we conclude that the AGN-powered VLBI sources are associated with compact nuclear starburst environments. The implications for possible starburst-AGN connections are discussed. The detected VLBI sources have a relatively narrow range of radio luminosity consistent with models in which intense compact Eddington-limited starbursts regulate the gas supply onto a central supermassive black hole. The high incidence of AGN radio cores in compact starbursts suggests little or no delay between the starburst phase and the onset of AGN activity

Astrometric Galactic maser measurements cross-matched with Gaia

Using the VLBA, the BeSSeL survey has provided distances and proper motions of young massive stars, allowing an accurate measure of the Galactic spiral structure. By the same technique, we are planning to map the inner Galaxy using positions and velocities of evolved stars (provided by the BAaDE survey). These radio astrometric measurements (BeSSeL and BAaDE) will be complementary to Gaia results and the overlap will provide important clues on the intrinsic properties and population distribution of the stars in the bulge.Comment: To appear in the Proceedings of the IAU Symposium No. 334: "Rediscovering our Galaxy

Maser, infrared and optical emission for late-type stars in the Galactic plane

Radio astrometric campaigns using VLBI have provided distances and proper motions for masers associated with young massive stars (BeSSeL survey). The ongoing BAaDE project plans to obtain astrometric information of SiO maser stars located in the inner Galaxy. These stars are associated with evolved, mass-losing stars. By overlapping optical (Gaia), infrared (2MASS, MSX and WISE) and radio (BAaDE) sources, we expect to obtain important clues on the intrinsic properties and population distribution of late-type stars. Moreover, a comparison of the Galactic parameters obtained with Gaia and VLBI can be done using radio observations on different targets: young massive stars (BeSSeL) and evolved stars (BAaDE).Comment: To appear in the Proceedings of the IAU Symposium No. 336: Astrophysical Masers: Unlocking the Mysteries of the Univers

Proper Motions of H2O Masers in the Water Fountain Source IRAS 19190+1102

We report on the results of two epochs of Very Long Baseline Array (VLBA) observations of the 22 GHz water masers toward IRAS 19190+1102. The water maser emission from this object shows two main arc-shaped formations perpendicular to their NE-SW separation axis. The arcs are separated by ~280 mas in position, and are expanding outwards at an angular rate of 2.35 mas/yr. We detect maser emission at velocities between -53.3 km/s to +78.0 km/s and there is a distinct velocity pattern where the NE masers are blueshifted and the SW masers are redshifted. The outflow has a three-dimensional outflow velocity of 99.8 km/s and a dynamical age of about 59 yr. A group of blueshifted masers not located along the arcs shows a change in velocity of more than 35 km/s between epochs, and may be indicative of the formation of a new lobe. These observations show that IRAS 19190+1102 is a member of the class of "water fountain"' pre-planetary nebulae displaying bipolar structureComment: Accepted for publication in ApJ, corrected typo

Long-period maser-bearing Miras in the Galactic center: period-luminosity relations and extinction estimates

We establish a sample of 370 Mira variables that are likely near the Galactic center (GC). The sources have been selected from the OGLE and BAaDE surveys based on their sky coordinates, OGLE classifications, and BAaDE maser-derived line-of-sight velocities. As the distance to the GC is known to a high accuracy, this sample is a test bed for reddening and extinction studies toward the GC and in Mira envelopes. We calculated separate interstellar- and circumstellar-extinction values for individual sources, showing that there is a wide range of circumstellar extinction values (up to four magnitudes in the K$_s$ band) in the sample, and that circumstellar reddening is statistically different from interstellar reddening laws. Further, the reddening laws in the circumstellar environments of our sample and the circumstellar environments of Large Magellanic Cloud (LMC) Miras are strikingly similar despite the different metallicities of the samples. Period-magnitude relations for the mid-infrared (MIR) WISE and MSX bands are also explored, and in the WISE bands we compare these to period-magnitude relationships derived from Miras in the LMC as it is important to compare these LMC relations to those in a higher metallicity environment. Emission from the envelope itself may contaminate MIR magnitudes altering the relations, especially for sources with thick envelopes.Comment: 14 pages, 10 figures; accepted to A&

Observations of HI Absorbing Gas in Compact Radio Sources at Cosmological Redshifts

We present an overview of the occurrence and properties of atomic gas associated with compact radio sources at redshifts up to z=0.85. Searches for HI 21cm absorption were made with the Westerbork Synthesis Radio Telescope at UHF-high frequencies (725-1200 MHz). Detections were obtained for 19 of the 57 sources with usable spectra (33%). We have found a large range in line depths, from tau=0.16 to tau<=0.001. There is a substantial variety of line profiles, including Gaussians of less than 10km/s, to more typically 150km/s, as well as irregular and multi-peaked absorption profiles, sometimes spanning several hundred km/s. Assuming uniform coverage of the entire radio source, we obtain column depths of atomic gas between 1e19 and 3.3e21(Tsp/100K)(1/f)cm^(-2). There is evidence for significant gas motions, but in contrast to earlier results at low redshift, there are many sources in which the HI velocity is substantially negative (up to v=-1420km/s) with respect to the optical redshift, suggesting that in these sources the atomic gas, rather than falling into the centre, may be be flowing out, interacting with the jets, or rotating around the nucleus.Comment: 10 pages, accepted for publication in A&