ABSTRACT. A brief description is given of the GLIMPSE surveys, including the areas surveyed, sensitivity limits, and products. The primary motivations for this review are to describe some of the main scientific results enabled by the GLIMPSE surveys and to note potential future applications of the GLIMPSE catalogs and images. In particular, we discuss contributions to our understanding of star formation and early evolution, the interstellar medium, galactic structure, and evolved stars. Infrared dark clouds (IRDCs), young stellar objects (YSOs), and infrared bubbles/H II regions are discussed in some detail. A probable triggered star formation associated with expanding infrared bubbles is briefly mentioned. The distribution and morphologies of dust and polycyclic aromatic hydrocarbons (PAHs) in the interstellar medium are discussed. Examples are shown from GLIMPSE images of bow shocks, pillars (elephant trunks), and instabilities in massive star-formation regions. The infrared extinction law of diffuse interstellar dust is discussed. The large-scale structure of the Galaxy has been traced by red-clump giants using the GLIMPSE point-source catalog to reveal the radius and orientation of the central bar, the stellar radial scale length, an obvious increase in star counts toward the tangency to the Scutum-Centaurus spiral arm, the lack of an obvious tangency from star counts toward the Sagittarius spiral arm, and a sharp increase in star counts toward the nuclear bulge. Recent results on evolved stars and some serendipitous discoveries are mentioned. More than 70 refereed papers have been published based on GLIMPSE data as of 2008 November.

A visual examination of the images from the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) has revealed 322 partial and closed rings that we propose represent partially or fully enclosed three-dimensional bubbles. We argue that the bubbles are primarily formed by hot young stars in massive star formation regions. We have found an average of about 1.5 bubbles per square degree. About 25% of the bubbles coincide with known radio H ii regions, and about 13% enclose known star clusters. It appears that B4-B9 stars (too cool to produce detectable radio H ii regions) probably produce about three-quarters of the bubbles in our sample, and the remainder are produced by young O-B3 stars that produce detectable radio H ii regions. Some of the bubbles may be the outer edges of H ii regions where PAH spectral features are excited and may not be dynamically formed by stellar winds. Only three of the bubbles are identified as known SNRs. No bubbles coincide with known planetary nebulae or W-R stars in the GLIMPSE survey area. The bubbles are small. The distribution of angular diameters peaks between 1 0 and 3 0 with over 98% having angular diameters less than 10 0 and 88% less than 4 0. Almost 90% have shell thicknesses between 0.2 and 0.4 of their outer radii. Bubble shell thickness increases approximately linearly with shell radius. The eccentricities are rather large, peaking between 0.6 and 0.7; about 65% have eccentricities between 0.55 and 0.85.

Using images from the Spitzer Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE), we have identified more than 300 extended 4.5 μm sources (Extended Green Objects (EGOs), for the common coding of the [4.5] band as green in three-color composite InfraRed Array Camera images). We present a catalog of these EGOs, including integrated flux density measurements at 3.6, 4.5, 5.8, 8.0, and 24 μm from GLIMPSE and the Multiband Imaging Photometer for Spitzer Galactic Plane Survey. The average angular separation between a source in our sample and the nearest IRAS point source is greater than 1 . The majority of EGOs are associated with infrared dark clouds (IRDCs), and where high-resolution 6.7 GHz CH 3 OH maser surveys overlap the GLIMPSE coverage, EGOs and 6.7 GHz CH 3 OH masers are strongly correlated. Extended 4.5 μm emission is thought to trace shocked molecular gas in protostellar outflows; the association of EGOs with IRDCs and 6.7 GHz CH 3 OH masers suggests that the extended 4.5 μm emission may pinpoint outflows specifically from massive protostars. The mid-IR colors of EGOs lie in regions of color-color space occupied by young protostars still embedded in infalling envelopes.

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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 0.4 Jy to 60 Jy 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 the flux density distribution of sources follows a power law with dN/dS ∝ S −2.4±0.1 and that the mean Galactic latitude for sources is significantly below the midplane: b = (−0.095 ± 0.001) • .

We present the Bolocam Galactic Plane Survey (BGPS), a 1.1 mm continuum survey at 33 effective resolution of 170 square degrees of the Galactic Plane visible from the northern hemisphere. The BGPS is one of the first large area, systematic surveys of the Galactic Plane in the millimeter continuum without arXiv:1011.0691v1 [astro-ph.GA] 2 Nov 2010 -2pre-selected targets. The survey is contiguous over the range −10.5 ≤ l ≤ 90.5, |b| ≤ 0.5. Towards the Cygnus X spiral arm, the coverage was flared to |b| ≤ 1.5 for 75.5 ≤ l ≤ 87.5. In addition, cross-cuts to |b| ≤ 1.5 were made at l = 3, 15, 30 and 31. The total area of this section is 133 square degrees. With the exception of the increase in latitude, no pre-selection criteria were applied to the coverage in this region. In addition to the contiguous region, four targeted regions in the outer Galaxy were observed: IC1396 (9 square degrees, 97.5 ≤ l ≤ 100.5, 2.25 ≤ b ≤ 5.25), a region towards the Perseus Arm (4 square degrees centered on l = 111, b = 0 near NGC7538), W3/4/5 (18 square degrees, 132.5 ≤ l ≤ 138.5) and Gem OB1 (6 square degrees, 187.5 ≤ l ≤ 193.5).The survey has detected approximately 8400 clumps over the entire area to a limiting non-uniform 1-σ noise level in the range 11 to 53 mJy beam −1 in the inner Galaxy. The BGPS source catalog is presented in a companion paper (Rosolowsky et al. 2010). This paper details the survey observations and data reduction methods for the images. We discuss in detail the determination of astrometric and flux density calibration uncertainties and compare our results to the literature. Data processing algorithms that separate astronomical signals from time-variable atmospheric fluctuations in the data time-stream are presented. These algorithms reproduce the structure of the astronomical sky over a limited range of angular scales and produce artifacts in the vicinity of bright sources. Based on simulations, we find that extended emission on scales larger than about 5. 9 is nearly completely attenuated (> 90%) and the linear scale at which the attenuation reaches 50% is 3. 8. Comparison with other millimeterwave data sets implies a possible systematic offset in flux calibration, for which no cause has been discovered.This presentation serves as a companion and guide to the public data release 1 through NASA's Infrared Processing and Analysis Center (IPAC) Infrared Science Archive (IRSA). New data releases will be provided through IPAC-IRSA with any future improvements in the reduction. The BGPS provides a complementary long-wavelength spectral band for the ongoing ATLASGAL and Herschel-SPIRE surveys, and an important database and context for imminent observations with SCUBA-2 and ALMA.

We present a new catalogue of 5106 infrared bubbles created through visual classification via the online citizen science website 'The Milky Way Project'. Bubbles in the new catalogue have been independently measured by at least five individuals, producing consensus parameters for their position, radius, thickness, eccentricity and position angle. Citizen scientists -volunteers recruited online and taking part in this research -have independently rediscovered the locations of at least 86 per cent of three widely used catalogues of bubbles and H II regions whilst finding an order of magnitude more objects. 29 per cent of the Milky Way Project catalogue bubbles lie on the rim of a larger bubble, or have smaller bubbles located within them, opening up the possibility of better statistical studies of triggered star formation. Also outlined is the creation of a 'heat map' of star formation activity in the Galactic plane. This online resource provides a crowd-sourced map of bubbles and arcs in the Milky Way, and will enable better statistical analysis of Galactic star formation sites.

We present the results of a GBT survey of NH 3 (1,1), (2,2), (3,3) lines towards 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 towards 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 − 5 kpc. 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. We have examined the physical properties as a function of Galactocentric distance, and find a mean gas kinetic temperature of 15.6 K, and that the NH 3 column density and abundance decrease by nearly an order of magnitude between R Gal ∼ 3 − 11 kpc. Comparing sources at similar distances demonstrates that the physical properties are indistinguishable, which suggests a similarity in clump structure across the Galactic disk. We have also compared the BGPS sources to criteria for efficient star formation presented independently by Heiderman et al. and Lada et al., and massive star formation presented by Kauffmann et al. 48% 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-IR source.