Serpens/Aquila Rift

Serpens/Aquila Rift
Name	Serpens/Aquila Rift
Constellation	Serpens, Aquila

Serpens/Aquila Rift is a complex, obscuring band of interstellar dust and molecular gas straddling the constellations Serpens and Aquila. It forms a prominent dark region against the Milky Way visible in optical surveys and is associated with active star-forming regions cataloged in radio, infrared, and X-ray studies. The Rift influences sightlines toward the Galactic Center, affects distance determinations used in mapping the Local Arm, and has been a target for multiwavelength campaigns by observatories such as Spitzer Space Telescope, James Clerk Maxwell Telescope, and Chandra X-ray Observatory.

Overview

The structure commonly described as the Rift appears in optical photographic surveys alongside features like the Great Rift and interleaves with emission nebulae cataloged by Messier and NGC. Research teams from institutions including the National Radio Astronomy Observatory and the European Southern Observatory have used the Rift to study the interplay between molecular clouds cataloged in the Barnard Catalogue and embedded stellar populations identified by the Two Micron All Sky Survey and the Wide-field Infrared Survey Explorer. The region has been referenced in major projects such as the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire and the CO Galactic Plane Survey.

Location and Structure

The Rift extends across Galactic longitudes that intersect the constellations Serpens Caput, Serpens Cauda, and Aquila, lying near sightlines toward the Scutum-Centaurus Arm and the Galactic Center. Its morphology is mapped using CO and dust continuum observations from facilities like the IRAM 30m Telescope, Atacama Pathfinder Experiment, and the Submillimeter Array, revealing filamentary structures comparable to those in the Taurus Molecular Cloud and Orion Molecular Cloud Complex. The Rift encompasses several dark clouds listed in the Lynds Dark Nebula catalogue and overlaps catalog entries from the Planck Catalogue of Galactic Cold Clumps.

Star Formation and Molecular Clouds

Embedded within the Rift are molecular clouds with masses estimated from CO surveys by the FCRAO and the CfA 1.2 m Millimeter-Wave Telescope, showing active low- and intermediate-mass star formation similar to that in Perseus Molecular Cloud and Ophiuchus Cloud Complex. Protostellar objects detected by Spitzer Space Telescope and Herschel Space Observatory surveys are associated with young stellar objects classified with schemes developed by the Harvard–Smithsonian Center for Astrophysics and the Max Planck Institute for Astronomy. Observations of molecular tracers such as HCN and NH3 using the Green Bank Telescope and the Nobeyama Radio Observatory have constrained densities and kinematics comparable to regions studied by the Carnegie Institution for Science and the Smithsonian Astrophysical Observatory.

Notable Objects and Subregions

Prominent dark clouds and star-forming cores within the Rift correspond to catalogued objects such as entries in the Barnard Catalogue and the Clemens and Barvainis globule lists; nearby emission regions include complexes cataloged in the Sharpless Catalog and HII regions mapped by the Very Large Array. Subregions linked to historical surveys include fields targeted by the Palomar Observatory Sky Survey and follow-up spectroscopy by the Keck Observatory and the European Southern Observatory's Very Large Telescope. Herbig–Haro objects and jets identified in the Rift have been imaged by the Hubble Space Telescope and ground-based adaptive optics systems from facilities like Gemini Observatory.

Observational History and Surveys

The Rift has been recognized since early photographic atlases such as those by Edward Emerson Barnard and was systematically catalogued in the mid-20th century by teams at the Mount Wilson Observatory and the Lick Observatory. Modern characterization has relied on multiwavelength surveys including the Galactic Plane Infrared Polarization Survey, the Bolocam Galactic Plane Survey, and the Planck mission's dust emission maps. Spectroscopic surveys from the Sloan Digital Sky Survey and targeted campaigns with the Apache Point Observatory and the European Space Agency instrumentation have refined cloud velocities used in Galactic rotation models like those developed by researchers at the Max Planck Institute for Radio Astronomy.

Distance and Extinction Studies

Distances to components of the Rift have been constrained using trigonometric parallaxes from the Very Long Baseline Array and the European VLBI Network, photometric extinction mapping with data from the Gaia mission and the 2MASS catalogue, and reddening analyses coordinated with the Pan-STARRS survey. Extinction laws calibrated by teams at the STScI and the Institute for Astronomy, University of Hawaii have been applied to disentangle multiple cloud layers along sightlines overlapping the Scutum Cloud and the Aquila Rift nomenclature used in historical literature. These studies inform Galactic scale height determinations and comparisons with distances to maser sources catalogued by the BeSSeL Survey.

Impact on Galactic Structure and Research Importance

Because the Rift obscures starlight toward the inner Galaxy, it shapes interpretations of stellar density fields used by projects such as the Gaia-ESO Survey and the APOGEE program, and affects extinction corrections in studies by the Sloan Digital Sky Survey and the Two Micron All Sky Survey. Its molecular content and star formation activity provide empirical tests for theories developed at institutions like the Institute of Astronomy, Cambridge and the California Institute of Technology, and for numerical simulations run at centers including the Max Planck Institute for Astrophysics and the Princeton Center for Theoretical Science. The Rift remains a benchmark for cross-calibrating instruments on observatories such as the James Webb Space Telescope and radio arrays like the ALMA.

Category:Interstellar clouds