Star Formation

The majority of stars form in very active star forming regions where feedback from the most massive stars can photo-evaporate the disk of accreting young stellar objects (YSOs), so called proplyds, and thus affect the ongoing star formation. The exact impact of irradiation on proplyds thus has to be studied to understand how it limits mass accretion in these objects.

30 Doradus is an ideal laboratory for studying massive star-forming regions. To better understand these processes, multiple SOFIA instruments have mapped 30 Doradus at a variety of infrared bands. These include FIFI-LS maps of the [CII], [OI], [NII], and [OIII] lines, GREAT maps of the [13CII] isotope transition, and HAWC+ polarization maps at 53, 89, 154, and 214 μm.

Measurements of far infrared cooling lines are ideal tools for studying the interstellar medium (ISM, Wolfire et. al. 2003). The brightest of these cooling lines is often the 158 micron line from singly-ionized carbon, or the [CII] 158 μm line (Luhman et. al. 2003), making it a frequent target of study in both local and high-z galaxies (Léfvre et. al. 2020). This emission line can originate in a wide variety of ISM environments, which complicates the utility of [CII] as an indicator of ISM properties. This complication can be overcome by using velocity-resolved maps of both the [CII] emission and the 205 μm line of singly ionized nitrogen ([NII] 205 μm). Resolved [CII] 158 μm and [NII] 205 μm maps of three HII regions in M33 obtained by the GREAT instrument onboard SOFIA are currently available on the IRS SOFIA Archive. These detailed maps are useful for a wide variety of studies of ISM conditions relating to star formation.

To study the early stages of star formation, the SOFIA archive hosts a wealth of data on the young protostellar object NGC7538 IRS1. These include: images at 7.7, 19.7, 25.3, 31.5 and 37.1 µm from FORCAST, spectral maps covering 75-95 µm and 135-155 µm from FIFI-LS, and high-resolution spectra from 5.5 to 27 µm from EXES. These rich datasets provide key tracers of young stellar envelops and are currently processed and available through IRSA.

The Arches Cluster, one of the densest star cluster in our galaxy, is located within the Galactic Center’s Central Molecular Zone, just about 25 pc from Sagittarius A*. Maps of this cluster are available through the SOFIA archive, including: spectrally-resolved maps of the [CII] line from GREAT, wide-field maps of the [CII] and [NIII] 57 µm lines from FIFI-LS, and 25 µm and 37 µm FORCAST maps.

Understanding and quantifying the effects of feedback in massive star-forming regions is an essential step in decoding galaxy evolution. In pursuit of this goal, the GREAT instrument has mapped the [CII] 158 µm and [OI] 63 µm lines in massive Milky Way star-forming regions as part of the FEEDBACK program.

Over the past several years, EXES observations have contributed to a rich inventory of mid-IR (5.5-8 µm) spectra from YSOs and protoplanetary disks. The available public database includes sources such as: GV Tau's disk, massive protostars AFGL 2136, AFGL 2591, massive star-forming region Orion IRc2, and high-mass YSOs NGC 7538 IRS 1 and IRS 9.

One of the nearest massive star forming regions, OMC-1, is situated just behind the Orion Nebula and has been extensively observed with all SOFIA instruments. Data accessible through the archive includes: HAWC+ photometric and polarization maps at 53, 89, 154, and 214 µm, GREAT ionized carbon [CII] velocity-resolved map at 158 µm, FORCAST and FLITECAM imaging of the Orion Bar at 3.3 and 11.2 µm, and FIFI-LS maps of mid-J CO lines between 69 and 200 µm. These images and maps are only a subset of the SOFIA observations of OMC-1 available.

The inaugural Legacy Program used the FORCAST instrument to observe the Galactic Center using the 25-micron and 37-micron bands. The data have unprecedented spatial resolution – six times higher than past observations — resulting in a vastly improved view of warm dust in the center of the galaxy and revealing signatures of star formation in exquisite detail.

The Carina Nebula is home to several massive star clusters and more than 65 O stars. Using the fully-sampled and velocity-resolved GREAT [OI] and CO maps of these pillars, scientists can probe the kinematics, morphology, and physical conditions within these interesting regions.

Data for an unprecedented infrared polarimetric analysis of the 30 Doradus star-forming region in the Large Magellanic Cloud were taken by HAWC+. At the center is a cluster of O-type and Wolf-Rayet stars that heat the surrounding dust, allowing for in-depth total intensity and polarimetry analysis of star formation in the infrared. SOFIA compiled polarization maps taken at 53, 89, 154, and 214 µm, revealing dust emission between 10-100 K and allowing for an inferred morphology study of the magnetic field.

The Horsehead Nebula (also known as Barnard 33) is a dark nebula and photodissociation region in the Orion Molecular Cloud Complex that is illuminated by the O9.5V star Sigma Orionis. To demonstrate the unique and important scientific capabilities of SOFIA, the upGREAT instrument has provided a velocity resolved map of the Horsehead Nebula in the [C II] line at 158 μm.

The circumnuclear disk, a molecular gas disk surrounding the ionized gas of the Galactic center, gives us the unique opportunity to study spatially resolved molecular gas close to a massive black hole and investigate in detail the gas properties and the effects of the different local processes. The characterization of the molecular gas can be obtained with the CO excitation analysis, combining a sample of CO transitions.