We derive unbiased distance estimates for the Gaia-TGAS data set by correcting for the bias due to the distance dependence of the selection function, which we measure directly from the data. From these distances and proper motions, we estimate the vertical and azimuthal velocities, W and V_{phi}_, and angular momentum L_z_ for stars in the Galactic centre and anticentre directions. The resulting mean vertical motion W^-^ hows a linear increase with both V_{phi}_ and L_z_ at 10{sigma} significance. Such a trend is expected from and consistent with the known Galactic warp. This signal extends to stars with guiding centre radii R_g_<R_0_, placing the onset of the warp at R<=7kpc. At equally high significance, we detect a previously unknown wave-like pattern of W^-^ over guiding centre R_g_ with an amplitude ~1km/s and a wavelength ~2.5kpc. This pattern is present in both the centre and anticentre directions, consistent with a winding (corrugated) warp or bending wave, likely related to known features in the outer disc (TriAnd and Monoceros overdensities), and may be caused by the interaction with the Sgr dwarf galaxy ~1Gyr ago. The only significant deviation from this simple fit is a stream-like feature near R_g_~9kpc (|L_z_|~2150kpc.km/s).
We present the results of a Green Bank Telescope survey of NH_3_(1,1), (2,2), (3,3) lines toward 631 Bolocam Galactic Plane Survey (BGPS) sources at a range of Galactic longitudes in the inner Galaxy. We have detected the NH_3_(1,1) line toward 72% of our targets (456), demonstrating that the high column density features identified in the BGPS and other continuum surveys accurately predict the presence of dense gas. We have determined kinematic distances and resolved the distance ambiguity for all BGPS sources detected in NH_3_. The BGPS sources trace the locations of the Scutum and Sagittarius spiral arms, with the number of sources peaking between R_Gal_~4 and 5kpc. We measure the physical properties of each source and find that depending on the distance, BGPS sources are primarily clumps, with some cores and clouds. Forty-eight percent of our sample should be forming stars (including massive stars) with high efficiency, and 87% contain subregions that should be efficiently forming stars. Indeed, we find that 67% of the sample exhibit signs of star formation activity based on an association with a mid-infrared source.
The Bolocam Galactic Plane Survey (BGPS) is a 1.1 mm continuum survey of dense clumps of dust throughout the Galaxy covering 170deg^2^. We present spectroscopic observations using the Heinrich Hertz Submillimeter Telescope of the dense gas tracers, HCO^+^ and N_2_H^+^3-2, for all 6194 sources in the BGPS v1.0.1 catalog between 7.5{deg}<=l<=194{deg}. This is the largest targeted spectroscopic survey of dense molecular gas in the Milky Way to date. We find unique velocities for 3126 (50.5%) of the BGPS v1.0.1 sources observed. Strong N_2_H^+^ 3-2 emission (T_mb_>0.5K) without HCO^+^ 3-2 emission does not occur in this catalog. We characterize the properties of the dense molecular gas emission toward the entire sample. HCO^+^ is very sub-thermally populated and the 3-2 transitions are optically thick toward most BGPS clumps. The median observed line width is 3.3 km/s consistent with supersonic turbulence within BGPS clumps. We find strong correlations between dense molecular gas integrated intensities and 1.1 mm peak flux and the gas kinetic temperature derived from previously published NH_3_observations. These intensity correlations are driven by the sensitivity of the 3-2 transitions to excitation conditions rather than by variations in molecular column density or abundance. We identify a subset of 113 sources with stronger N_2_H^+^ than HCO^+^ integrated intensity, but we find no correlations between the N_2_H^+^/HCO^+^ ratio and 1.1 mm continuum flux density, gas kinetic temperature, or line width. Self-absorbed profiles are rare (1.3%).
The Bolocam Galactic Plane Survey (BGPS) data for a 6deg^2^ region of the Galactic plane containing the Galactic center are analyzed and compared to infrared and radio continuum data. The BGPS 1.1mm emission consists of clumps interconnected by a network of fainter filaments surrounding cavities, a few of which are filled with diffuse near-IR emission indicating the presence of warm dust or with radio continuum characteristic of HII regions or supernova remnants. New 350um images of the environments of the two brightest regions, Sgr A and B, are presented. Sgr B2 is the brightest millimeter-emitting clump in the Central Molecular Zone (CMZ) and may be forming the closest analog to a super star cluster in the Galaxy. The CMZ contains the highest concentration of millimeter- and submillimeter-emitting dense clumps in the Galaxy. Most 1.1mm features at positive longitudes are seen in silhouette against the 3.6-24um background observed by the Spitzer Space Telescope. However, only a few clumps at negative longitudes are seen in absorption, confirming the hypothesis that positive longitude clumps in the CMZ tend to be on the near side of the Galactic center, consistent with the suspected orientation of the central bar in our Galaxy. The Bolocat catalog of 1.1mm clumps contains 1428 entries in the Galactic center between l=358.5{deg} and l=4.5{deg} of which about 80% are likely to be within about 500pc of the center.
We present a catalog of 8358 sources extracted from images produced by the Bolocam Galactic Plane Survey (BGPS). The BGPS is a survey of the millimeter dust continuum emission from the northern Galactic plane. The catalog sources are extracted using a custom algorithm, Bolocat, which was designed specifically to identify and characterize objects in the large-area maps generated from the Bolocam instrument. The catalog products are designed to facilitate follow-up observations of these relatively unstudied objects. The catalog is 98% complete from 0.4Jy to 60Jy over all object sizes for which the survey is sensitive (<3.5'). We find that the sources extracted can best be described as molecular clumps-large dense regions in molecular clouds linked to cluster formation. We find that the flux density distribution of sources follows a power law with dN/dS{prop.to}S^-2.4+/-0.1^ and that the mean Galactic latitude for sources is significantly below the midplane: <b>=(-0.095+/-0.001{deg}).
The ensemble of chemical element abundance measurements for stars, along with precision distances and orbit properties, provides high-dimensional data to study the evolution of the MilkyWay.With this third data release of the Galactic Archaeology with HERMES (GALAH) survey, we publish 678 423 spectra for 588 571 mostly nearby stars (81.2 per cent of stars are within <2 kpc), observed with the HERMES spectrograph at the Anglo-Australian Telescope. This release (hereafter GALAH+ DR3) includes all observations from GALAH Phase 1 (bright, main, and faint survey, 70 per cent), K2-HERMES (17 per cent), TESS-HERMES (5 per cent), and a subset of ancillary observations (8 per cent) including the bulge and >75 stellar clusters. We derive stellar parameters Teff, logg, [Fe/H], vmic, vbroad, and vrad using our modified version of the spectrum synthesis code Spectroscopy Made Easy (SME) and 1D MARCS model atmospheres. We break spectroscopic degeneracies in our spectrum analysis with astrometry from Gaia DR2 and photometry from 2MASS. We report abundance ratios [X/Fe] for 30 different elements (11 of which are based on non-LTE computations) covering five nucleosynthetic pathways. We describe validations for accuracy and precision, flagging of peculiar stars/measurements and recommendations for using our results. Our catalogue comprises 65 per cent dwarfs, 34 per cent giants, and 1 per cent other/unclassified stars. Based on unflagged chemical composition and age, we find 62 per cent young low-alpha, 9 per cent young high-alpha, 27 per cent old high-alpha, and 2 per cent stars with [Fe/H]<=-1. Based on kinematics, 4 per cent are halo stars. Several Value-Added-Catalogues, including stellar ages and dynamics, updated after Gaia eDR3, accompany this release and allow chrono-chemodynamic analyses, as we showcase.
We present time-series BVI photometry for the Galactic globular cluster NGC 6402 (M14). The data consist of ~137 images per filter, obtained using the 0.9 and 1.0 m SMARTS telescopes at the Cerro Tololo Inter-American Observatory. The images were obtained during two observing runs in 2006-2007. The image-subtraction package ISIS, along with DAOPHOT II/ALLFRAME, was used to perform crowded-field photometry and search for variable stars. We identified 130 variables, eight of which are new discoveries. The variable star population is comprised of 56 ab-type RR Lyrae stars, 54 c-type RR Lyrae, 6 type II Cepheids, 1 W UMa star, 1 detached eclipsing binary, and 12 long-period variables. We provide Fourier decomposition parameters for the RR Lyrae, and discuss the physical parameters and photometric metallicity derived therefrom. The M14 distance modulus is also discussed, based on different approaches for the calibration of the absolute magnitudes of RR Lyrae stars. The possible presence of second-overtone RR Lyrae in M14 is critically addressed, with our results arguing against this possibility. By considering all of the RR Lyrae stars as members of the cluster, we derive <P_ab_>=0.589 days. This, together with the position of the RR Lyrae stars of both Bailey types in the period-amplitude diagram, suggests an Oosterhoff-intermediate classification for the cluster. Such an intermediate Oosterhoff type is much more commonly found in nearby extragalactic systems, and we critically discuss several other possible indications that may point to an extragalactic origin for this cluster.
The ISOGAL survey is one of the largest imaging programme performed by the ISO satellite. About 16deg^2^ mainly distributed in the inner Galactic disk were mapped at 7 and/or 15 micron ({mu}m). Because of highly structured background and high source density, a special point source extraction algorithm was used and resulted in a 100000 point source catalogue. The mid-infrared data have been associated with near-infrared DENIS sources, providing an up to five wavelength photometric catalogue with a typical astrometric accuracy better than 1 arcsecond. The point source catalogue contains the positional and photometric parameters of all ISOGAL sources, together with various quality flags aimed at giving an estimate of the reliability of the detections and of the associations between the different bands (see the paper for a complete description).
We present a catalog of compact sources derived from the QUaD Galactic Plane Survey. The survey covers ~800deg^2^ of the inner galaxy (|b|<4{deg}) in Stokes I, Q, and U parameters at 100 and 150GHz, with angular resolutions of 5 and 3.5 arcmin, respectively. Five hundred and twenty-six unique sources are identified in I, of which 239 are spatially matched between frequency bands, with 53 (234) detected at 100 (150)GHz alone; 170 sources are identified as ultracompact HII regions. Four sources are detected in polarized intensity P, of which three have matching counterparts in I. Three of the polarized sources lie close to the Galactic center, Sagittarius A*, Sagittarius B2, and the Galactic Radio Arc, while the fourth is RCW 49, a bright HII region. An extended polarized source, undetected by the source extraction algorithm on account of its ~0.5{deg} size, is identified visually, and is an isolated example of large-scale polarized emission oriented distinctly from the bulk Galactic dust polarization.
We investigate the orbital motion of the Quintuplet cluster near the Galactic center with the aim of constraining formation scenarios of young, massive star clusters in nuclear environments. Three epochs of adaptive optics high-angular resolution imaging with the Keck/NIRC2 and Very Large Telescope/NAOS-CONICA systems were obtained over a time baseline of 5.8 yr, delivering an astrometric accuracy of 0.5-1 mas/yr. Proper motions were derived in the cluster reference frame and were used to distinguish cluster members from the majority of the dense field star population toward the inner bulge. Fitting the cluster and field proper motion distributions with two-dimensional (2D) Gaussian models, we derive the orbital motion of the cluster for the first time. The Quintuplet is moving with a 2D velocity of 132+/-15 km/s with respect to the field along the Galactic plane, which yields a three-dimensional orbital velocity of 167+/-15 km/s when combined with the previously known radial velocity. From a sample of 119 stars measured in three epochs, we derive an upper limit to the velocity dispersion of {sigma}_1D_< 10 km/s in the core of the Quintuplet cluster. Knowledge of the three velocity components of the Quintuplet allows us to model the cluster orbit in the potential of the inner Galaxy. Under the assumption that the Quintuplet is located in the central 200 pc at the present time, these simulations exclude the possibility that the cluster is moving on a circular orbit. Comparing the Quintuplet's orbit with our earlier measurements of the Arches' orbit, we discuss the possibility that both clusters originated in the same area of the central molecular zone (CMZ). According to the model of Binney et al., two families of stable cloud orbits are located along the major and minor axes of the Galactic bar, named x1 and x2 orbits, respectively. The formation locus of these clusters is consistent with the outermost x2 orbit and might hint at cloud collisions at the transition region between the x1 and x2 orbital families located at the tip of the minor axis of the Galactic bar. The formation of young, massive star clusters in circumnuclear rings is discussed in the framework of the channeling in of dense gas by the bar potential. We conclude that the existence of a large-scale bar plays a major role in supporting ongoing star and cluster formation, not only in nearby spiral galaxies with circumnuclear rings, but also in the Milky Way's CMZ.
