Recent models and simulations of cluster formation within molecular clumps consider multi-scale, hierarchical accretion, which leads to clump mass growth over time. This mode of mass accumulation could have implications regarding the evolution of observable properties such as mass and radius, bringing into question the interpretation of commonly cited thresholds for high-mass star formation. In this paper, we use the conveyor belt model of cluster formation to create synthetic cores/clumps and derive physical and observational properties. We show that while this model successfully predicts many observed trends, modifications are required to match properties of high-mass prestellar clumps. When the model clumps are observationally classified as intermediate- or high-mass star-forming, the threshold delineating these two groups agrees with those found in the literature; however, results show that high-mass clumps at early evolutionary stages can be misclassified using standard surface density thresholds. Our logistic regression analysis reveals the quantity of material to ever enter a star-forming region is the most important factor in differentiating intermediate- and high-mass star-forming regions. This implies observations characterising the environment surrounding star-forming regions are crucial, especially at early evolutionary stages.

We present spectroscopic evidence for tidal debris associated with the bulge globular cluster NGC 6569, based on medium-resolution (R similar to 11,000) spectra of 303 stars obtained with the Anglo-Australian Telescope. Targets were selected using Blanco DECam Bulge Survey photometry with Gaia DR3 astrometry, and span similar to 7 ' - 30 ' (i.e., 1-5 rt, where rt is the King-model tidal radius) from the cluster center. Theoretical modeling shows that the Jacobi radii can vary between 8 ' - 11 ' and 18 ' - 22 ' over the orbit, likely leaving stars around the cluster that are transitioning into the predicted leading and lagging tidal tails. We identify 40 stars in this sample that exhibit chemical and kinematic properties consistent with previous, or borderline, cluster membership. The seven best candidates have S/N > 30, with [Fe/H] = -0.83 +/- 0.14 dex and [alpha/Fe] = +0.38 +/- 0.06 dex, consistent with NGC 6569's bound population. Our findings provide evidence that NGC 6569 is actively losing stars through tidal stripping, contributing to the bulge field population at a present rate of 1.0-1.6 M-circle dot Myr(-1), which corresponds to approximate to 5.6% +/- 1.3% of its present-day mass per Gyr. This work is part of the Milky Way Bulge Extra-Tidal Star Survey and represents our first detailed study of a massive bulge globular cluster in this context.

We describe the construction and use of the Mid-InfraRed Interstellar Objects and Nebulae (MIRION) catalog, which was compiled from 6176 objects identified as “yellowballs” (YBs) by participants in the Milky Way Project. The majority of YBs are compact photodissociation regions generated by intermediate- and high-mass young stellar objects that are embedded in star-forming clumps ranging in mass from 10 to 10 ^6 M _⊙ and luminosity from 10 to 10 ^4 L _⊙ . The MIRION catalog increases the number of candidate intermediate-mass star-forming regions (SFRs) by nearly 2 orders of magnitude, providing an extensive database with which to explore the transition from isolated low-mass to clustered high-mass star formation. The catalog comprises five tables that include mid- and far-infrared photometry, velocities of source-associated molecular clouds, distances to these molecular clouds, physical properties of source-associated star-forming clumps, and source crossmatches with other catalogs. The structure of the catalog enables users to easily sort objects for further study based on distance or environmental properties. Our preliminary analysis extends our earlier findings that indicate a relationship between infrared (IR) colors and the physical properties and evolutionary stages of SFRs. Photometry will be periodically updated online to incorporate measurements from volunteers participating in a classroom activity known as the People Enabling Research: a Yellowball Survey of the Colors Of Protostellar Environments (or PERYSCOPE) project. These updates will continue to refine the IR flux measurements and reduce photometric errors. A follow-up paper will present a detailed analysis of how IR colors can be used to predict the properties of star-forming environments.

We review participatory science programs that have contributed to the understanding of star formation. The Milky Way Project (MWP), one of the earliest participatory science projects launched on the Zooniverse platform, produced the largest catalog of “bubbles” associated with feedback from hot young stars to date, and enabled the identification of a new class of compact star-forming regions (SFRs) known as “yellowballs” (YBs). The analysis of YBs through their infrared colors and catalog cross-matching led to discovering that YBs are compact photodissociation regions generated by intermediate- and high-mass young stellar objects embedded in clumps that range in mass from 10 - 104 M⊙ and luminosity from 10 - 106 L⊙. The MIRION catalog, assembled from 6176 YBs identified by citizen scientists, increases the number of candidate intermediate-mass SFRs by nearly two orders of magnitude. Ongoing work utilizing data from the Spitzer, Herschel and WISE missions involves analyzing infrared color trends to predict physical properties and ages of YB environments. Methods include applying summary statistics to histograms and color-color plots as well as SED fitting. Students in introductory astronomy classes contribute toward continued efforts refining photometric measurements of YBs while learning fundamental concepts in astronomy through a classroom-based participatory science experience, the PERYSCOPE project. We also describe an initiative that engaged seminaries, family groups, and interfaith communities in a wide variety of science projects on the Zooniverse platform. This initiative produced important guidance on attracting audiences that are underserved, underrepresented, or apprehensive about science.

We present a view of the stellar halo in the inner-central regions of the Milky Way ( R ≲ 10 kpc) mapped by RR Lyrae stars. The combined BRAVA-RR/APOGEE RR Lyrae catalog is used to obtain a sample of 281 RR Lyrae stars located in the bulge region of the Galaxy, but with orbits indicating they belong to the inner-central halo. The RR Lyrae stars in the halo are more metal-poor than the bulge RR Lyrae stars and have pulsation properties more consistent with an accreted population. We use the Milky Way-like zoom-in cosmological simulation Auriga to compare the properties of the RR Lyrae stars to those expected from the “Gaia-Enceladus-Sausage” (GES) merger. The integrals of motions and eccentricities of the RR Lyrae stars are consistent with a small fraction of 6–9% ± 2% of the inner-central halo RR Lyrae population having originated from GES. This fraction, lower than what is seen in the solar neighborhood, is consistent with trends seen in the Auriga simulation, where a GES-like merger would have a decreasing fraction of GES stars at small Galactocentric radii compared to other accreted populations. Very few of the Auriga inner Galaxy GES-18 particles have properties consistent with belonging to a bulge population with ( z _max < 1.1 kpc), indicating that no (or very few) RR Lyrae stars with bulge orbits should have originated from GES.

Here we present an automated method for obtaining wavelength calibrations for one-dimensional spectra, using Dynamic Time Warping (DTW). DTW is a flexible and well-understood algorithm for pattern matching, which has not been widely used in astronomy data analysis. Employing a calibrated template spectrum as a reference, DTW can recover non-linear and even discontinuous dispersion solutions without an initial guess. The algorithm is robust against differing spectral resolution between the template and sample data, and can accommodate some spurious or missing features. We demonstrate the effectiveness of DTW in an automated data reduction workflow, using both simulated and real arc lamp spectra in a Python data reduction framework. Finally, we provide a discussion on the utility and best practices with the DTW algorithm for wavelength calibration. We also introduce the PyKOSMOS data reduction toolkit, which includes our DTW calibration methods.

RR Lyrae stars (RRLs) are excellent tracers of stellar populations for old, metal-poor components in the the Milky Way and the Local Group. Their luminosities have a metallicity dependence, but determining spectroscopic [Fe/H] metallicities for RRLs, especially at distances outside the solar neighborhood, is challenging. Using 40 RRLs with metallicities derived from both Fe( ii ) and Fe( i ) abundances, we verify the calibration between the [Fe/H] of RRLs from the calcium triplet. Our calibration is applied to all RRLs with Gaia Radial Velocity Spectrometer (RVS) spectra in Gaia DR3 and to 80 stars in the inner Galaxy from the BRAVA-RR survey. The coadded Gaia RVS RRL spectra provide RRL metallicities with an uncertainty of 0.25 dex, which is a factor of two improvement over the Gaia photometric RRL metallicities. Within our Galactic bulge RRL sample, we find a dominant fraction with low energies without a prominent rotating component. Due to the large fraction of such stars, we interpret these stars as belonging to the in situ metal-poor Galactic bulge component, although we cannot rule out that a fraction of these belong to an ancient accretion event such as Kraken/Heracles.

The Milky Way Bulge extra-tidal star survey is a spectroscopic survey with the goal of identifying stripped globular cluster stars from inner Galaxy clusters. In this way, an indication of the fraction of metal-poor bulge stars that originated from globular clusters can be determined. We observed and analyzed stars in and around BH 261, an understudied globular cluster in the bulge. From seven giants within the tidal radius of the cluster, we measured an average heliocentric radial velocity of 〈RV〉 = −61 ± 2.6 km s ^−1 with a radial velocity dispersion of 〈 σ 〉 = 6.1 ± 1.9 km s ^−1 . The large velocity dispersion may have arisen from tidal heating in the cluster’s orbit about the Galactic center, or because BH 261 has a high dynamical mass as well as a high mass-to-light ratio. From spectra of five giants, we measure an average metallicity of 〈[Fe/H]〉 = −1.1 ± 0.2 dex. We also spectroscopically confirm an RR Lyrae star in BH 261, which yields a distance to the cluster of 7.1 ± 0.4 kpc. Stars with 3D velocities and metallicities consistent with BH 261 reaching to ∼0.°5 from the cluster are identified. A handful of these stars are also consistent with the spatial distribution of potential debris from models focusing on the most recent disruption of the cluster.

Patchick 99 is a candidate globular cluster located in the direction of the Galactic bulge, with a proper motion almost identical to the field and extreme field star contamination. A recent analysis suggests it is a low-luminosity globular cluster with a population of RR Lyrae stars. We present new spectra of stars in and around Patchick 99, targeting specifically the 3 RR Lyrae stars associated with the cluster as well as the other RR Lyrae stars in the field. A sample of 53 giant stars selected from proper motions and a position on CMD are also observed. The three RR Lyrae stars associated with the cluster have similar radial velocities and distances, and two of the targeted giants also have radial velocities in this velocity regime and [Fe/H] metallicities that are slightly more metal-poor than the field. Therefore, if Patchick 99 is a bonafide globular cluster, it would have a radial velocity of -92+/-10 km s-1, a distance of 6.7+/-0.4 kpc (as determined from the RR Lyrae stars), and an orbit that confines it to the inner bulge.

Yellowballs (YBs) were first discovered during the Milky Way Project (MWP) citizen science initiative. The MWP users noticed compact, yellow regions in Spitzer Space Telescope mid-infrared (MIR) images of the Milky Way plane and asked professional astronomers to explain these “yellow balls.” Follow-up work by Kerton et al. determined that YBs likely trace compact photodissociation regions associated with massive and intermediate-mass star formation. The YBs were included as target objects in a version of the MWP launched in 2016, which produced a listing of over 6000 YB locations. We have measured distances, cross-match associations, physical properties, and MIR colors of ∼500 YBs within a pilot region covering the l = 30°–40°, b = ±1° region of the Galactic plane. We find that ∼20%–30% of YBs in our pilot region contain high-mass star formation capable of becoming expanding H ii regions that produce MIR bubbles. A majority of YBs represent intermediate-mass star-forming regions whose placement in evolutionary diagrams suggest they are still actively accreting and may be precursors to optically revealed Herbig Ae/Be nebulae. Many of these intermediate-mass YBs were missed by surveys of massive star formation tracers; thus, this catalog provides information for many new sites of star formation. Future work will expand this pilot region analysis to the entire YB catalog.

We used the Green Bank Telescope to detect molecular lines observed toward mid-infrared bubbles N62, N65, N90, and N117. The bubbles were selected from Watson et al., who detected non-Gaussian CS (1–0) emission lines toward the bubbles. Two of the bubbles are adjacent to infrared dark clouds (IRDCs); we examined these sources for evidence of interaction between the bubble rim and IRDC. The other two bubbles contain young stellar objects (YSOs) interior to the bubble rim; in these sources, we observed the gas near the YSOs. We detect CS (1–0) emission toward all of the sources, and in several pointings the CS emission shows non-Gaussian line shapes. HC3N (5–4), C34S (1–0), CH3OH (1–0), and SiO (v = 0) (1–0) were also detected in some pointings. We calculate column densities and abundances for the detected molecules. We compare the velocity of optically thick CS emission with the velocity of the other optically thin lines to look for evidence of infall. We find that even in pointings with non-Gaussian CS emission, our detections do not support an infall model. We interpret the kinematics of the gas in N62, N65, and N117 as likely evidence of multiple clouds along the line of sight moving at slightly offset velocities. We do not detect evidence of bubble rims interacting with IRDCs in N62 or N90. The gas interior to bubbles appears more disrupted than the gas in the IRDCs. N65 shows significantly stronger emission lines than the other sources, as well as the most complicated non-Gaussian line shapes.

We survey 44 young stellar objects located near the edges of mid-IR-identified bubbles in CS (1-0) using the Green Bank Telescope. We detect emission in 18 sources, indicating young protostars that are good candidates for being triggered by the expansion of the bubble. We calculate CS column densities and abundances. Three sources show evidence of infall through non-Gaussian line-shapes. Two of these sources are associated with dark clouds and are promising candidates for further exploration of potential triggered star formation. We obtained on-the-fly maps in CS (1-0) of three sources, showing evidence of significant interactions between the sources and the surrounding environment.

Infrared Dark Clouds (IRDCs) harbor the earliest phases of massive star formation, and many of the compact cores in IRDCs, traced by millimeter continuum or by molecular emission in high critical density lines, host massive young stellar objects (YSOs). We used the Robert C. Byrd Green Bank Telescope and the Karl G. Jansky Very Large Array (VLA) to map NH3 and CCS in nine IRDCs to reveal the temperature, density, and velocity structures and explore chemical evolution in the dense (> 10(22) cm(-2)) gas. Ammonia is an excellent molecular tracer for these cold, dense environments. The internal structure and kinematics of the IRDCs include velocity gradients, filaments, and possibly colliding clumps that elucidate the formation process of these structures and their YSOs. We find a wide variety of substructure including filaments and globules at distinct velocities, sometimes overlapping at sites of ongoing star formation. It appears that these IRDCs are still being assembled from molecular gas clumps even as star formation has already begun, and at least three of them appear consistent with the morphology of "hub-filament structures" discussed in the literature. Furthermore, we find that these clumps are typically near equipartition between gravitational and kinetic energies, so these structures may survive for multiple free-fall times.

We present Very Large Array observations of ammonia (NH3) (1,1), (2,2), and dicarbon sulfide (CCS) (2(1)-1(0)) emission toward the infrared dark cloud (IRDC) G19.30+0.07 at similar to 22 GHz. The NH3 emission closely follows the 8 mu m extinction. The NH3 (1,1) and (2,2) lines provide diagnostics of the temperature and density structure within the IRDC, with typical rotation temperatures of similar to 10-20 K and NH3 column densities of similar to 10(15) cm(-2). The estimated total mass of G19.30+0.07 is similar to 1130M(circle dot). The cloud comprises four compact NH3 clumps of mass similar to 30-160M(circle dot). Two coincide with 24 mu m emission, indicating heating by protostars, and show evidence of outflow in the NH3 emission. We report a water maser associated with a third clump; the fourth clump is apparently starless. A non-detection of 8.4 GHz emission suggests that the IRDC contains no bright H II regions and places a limit on the spectral type of an embedded zero-age main-sequence star to early-B or later. From the NH3 emission, we find that G19.30+0.07 is composed of three distinct velocity components or "subclouds." One velocity component contains the two 24 mu m sources and the starless clump, another contains the clump with the water maser, while the third velocity component is diffuse, with no significant high-density peaks. The spatial distribution of NH3 and CCS emission from G19.30+0.07 is highly anti-correlated, with the NH3 predominantly in the high-density clumps and the CCS tracing lower-density envelopes around those clumps. This spatial distribution is consistent with theories of evolution for chemically young low-mass cores, in which CCS has not yet been processed to other species and/or depleted in high-density regions.