Leslie W Looney · University of Illinois Urbana-Champaign · PhdFit
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Leslie W Looney
· Director - Laboratory for Astronomical Imaging, ProfessorVerified
University of Illinois Urbana-Champaign · Astronomy
Leslie W. Looney is a Professor of Astronomy and a faculty member at the National Center for Supercomputing Applications (NCSA) at the University of Illinois. His research group focuses on studying protostars, which are young stars aged between 10,000 to 100,000 years, prior to the onset of hydrogen fusion in their cores. These protostars are enveloped by dust and gas, providing direct evidence of star formation processes and the early stages of planetary system development. Professor Looney's recent research interests include the evolution of circumstellar disks from their earliest stages and the impact of these disks on planet formation through dust grain growth. Additionally, his group investigates the polarization of light from circumstellar disks, which arises from mechanisms such as aligned dust grains influenced by magnetic fields, mechanical alignment of dust grains, and scattering effects. Due to the deeply embedded nature of the sources studied, observations are conducted at wavelengths longer than 10 microns, utilizing advanced facilities such as ALMA, JWST, and the VLA to explore stellar nurseries. Professor Looney has been recognized for his excellence in teaching, having been named to the "List of Teachers Ranked as Excellent" twenty times since 2004, and he teaches a variety of astronomy courses ranging from introductory astronomy to specialized topics like star formation and extraterrestrial life.
Data for the publication Protostellar Outflows Shed Light on the Dominant Close Companion Star Formation Pathways (Sponzilli et al). Contains the fits files, data files, and python scripts. The entire analysis is containerized with Docker. The `Dockerfile` in the root folder can be used to build the image. <b>Note:</b> __MACOSX folder or files starting with dot can be safely ignored or removed.
This dataset includes the FITS files for all ALMA images used in the ApJ publication "Multiband ALMA Polarization Observations of BHB 07-11 Reveal Aligned Dust Grains in Complex Spiral Arm Structures". Additionally, this dataset includes details regarding the data reduction process so that interested users can perform the reduction and imaging themselves.
The Astrophysical Journal · 2026-03-09 · 2 citations
articleOpen access
Abstract The earliest stages of star formation are highlighted by complex interactions between accretion, outflow, and radiative processes, which shape the chemical and physical environment of the emerging protostar. James Webb Space Telescope observations of the low-mass, low-luminosity Class 0 protostar IRAS 16253–2429 (I16253) reveal a central compact source. This object exhibits a rich mid-IR emission spectrum of OH pure rotational lines and CO 2 rovibrational lines. Unusually for a young stellar object, it has no mid-IR line emission from H 2 O to match the other molecules. We demonstrate that the emitting OH molecules arise from UV photodissociation of H 2 O in its second absorption band at λ = 114–145 nm, and that the OH emission is a fluorescent cascade starting with highest-excitation rotational states. This situation offers the opportunity of using the IR OH spectrum to measure the UV flux from the central protostar. Thereby, we determine the disk-to-star accretion rate to be 3 × 10 −10 M ⊙ yr −1 , and demonstrate that the system luminosity arises mostly from the protostar’s photosphere rather than from accretion luminosity. The result is in accord with the measured outflow rate of I16253 and lies within the outflow/accretion-flow rate trend often inferred for protostars, and with episodic accretion as the dominant mechanism by which this protostar has grown.
The Astrophysical Journal · 2025-10-01 · 3 citations
articleOpen access
Abstract We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of the Class 0 protostar IRAS 04166+2706, obtained as part of the ALMA Large Program Early Planet Formation in Embedded Disks. These observations were made in the 1.3 mm dust continuum and molecular lines at angular resolutions of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>∼</mml:mo> <mml:mn>0</mml:mn> <mml:mover accent="true"> <mml:mi>.</mml:mi> <mml:mi>″</mml:mi> </mml:mover> <mml:mn>05</mml:mn> </mml:math> (∼8 au) and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>∼</mml:mo> <mml:mn>0</mml:mn> <mml:mover accent="true"> <mml:mi>.</mml:mi> <mml:mi>″</mml:mi> </mml:mover> <mml:mn>16</mml:mn> </mml:math> (∼25 au), respectively. The continuum emission shows a disklike structure with a radius of ∼22 au. Kinematical analysis of 13 CO (2–1), C 18 O (2–1), H 2 CO (3 0,3 –2 0,2 ), CH 3 OH (4 2 –3 1 ) emission demonstrates that these molecular lines trace the infalling-rotating envelope and possibly a Keplerian disk, enabling us to estimate the protostar mass to be 0.15 M ⊙ < M ⋆ < 0.39 M ⊙ . The dusty disk is found to exhibit a brightness asymmetry along its minor axis in the continuum emission, probably caused by a flared distribution of the dust and the high optical depth of the dust emission. In addition, the 12 CO (2–1) and SiO (5–4) emissions show knotty and wiggling motions in the jets. Our high-angular-resolution observations revealed the most recent mass ejection events, which have occurred within the last ∼25 yr.
We present ALMA observations of the Class 0 protostar IRAS 04166+2706, obtained as part of the ALMA large program Early Planet Formation in Embedded Disks (eDisk). These observations were made in the 1.3 mm dust continuum and molecular lines at angular resolutions of $\sim 0.05''$ ($\sim 8$ au) and $\sim 0.16''$ ($\sim25$ au), respectively. The continuum emission shows a disk-like structure with a radius of $\sim22$ au. Kinematical analysis of $^{13}$CO(2-1), C$^{18}$O(2-1), H$_2$CO (3$_{0,3}$-2$_{0,2}$), CH$_3$OH (4$_2$-3$_1$) emission demonstrates that these molecular lines trace the infalling-rotating envelope and possibly a Keplerian disk, enabling us to estimate the protostar mass to be $0.15 \rm{M_\odot} < \rm{M_\star} < 0.39 M_\odot$. The dusty disk is found to exhibit a brightness asymmetry along its minor axis in the continuum emission, probably caused by a flared distribution of the dust and the high optical depth of the dust emission. In addition, the CO(2-1) and SiO(5-4) emissions show knotty and wiggling motions in the jets. Our high angular resolution observations revealed the most recent mass ejection events, which have occurred within the last $\sim 25$ years.
The earliest stages of star formation are highlighted by complex interactions between accretion, outflow, and radiative processes, which shape the chemical and physical environment of the emerging protostar. James Webb Space Telescope observations of the low-mass, low-luminosity Class 0 protostar IRAS 16253-2429 reveal a central compact source. This object exhibits a rich mid-infrared emission spectrum of OH pure rotational lines and $\rm CO_2$ ro-vibrational lines. Unusually for a young stellar object, it has no mid-infrared line emission from $\rm H_2O$ to match the other molecules. We demonstrate that the emitting OH molecules arise from UV photodissociation of $\rm H_2O$ in its second absorption band at $λ= 114-145$ nm, and that the OH emission is a fluorescent cascade starting with highest-excitation rotational states. This situation offers the opportunity of using the infrared OH spectrum to measure the UV flux from the central protostar. Thereby we determine the disk-star accretion rate to be $3 \times 10^{-10} \ M_\sun \ {\rm year^{-1}}$, and demonstrate that the system luminosity arises mostly from the protostar's photosphere rather than from accretion luminosity. The result is in accord with the measured outflow rate of IRAS 16253-2429 and lies within the outflow/accretion-flow rate trend often inferred for protostars; and with episodic accretion as the dominant mechanism by which this protostar has grown.
Polarization-mode observations from the Atacama Large Millimeter/submillimeter Array (ALMA) are powerful tools for studying the dust grain populations in circumstellar disks. Many sources exhibit polarization signatures consistent with aligned dust grains, yet the physical origin of this alignment remains uncertain. One such source is BHB07-11, a Class I protobinary object in the Pipe Nebula with complex spiral arm structures in its circumbinary disk. While magnetic fields are often invoked to explain grain alignment in the interstellar medium, the contrasting conditions in circumstellar disk environments demand further investigation into grain alignment mechanisms. To determine BHB07-11's dominant polarization mechanism, we leverage ALMA polarization-mode dust continuum observations in Bands 3 ($λ$=3.1 mm), 6 ($λ$=1.3 mm), and 7 ($λ$=0.87 mm), in combination with high-resolution dust continuum and spectral line observations in Band 6. Observed polarization vectors in each band are consistent with emission from aligned grains and follow the structure of the spiral arms as shown in the high-resolution observations. Given the relationship between the observed polarization vector orientation and the spiral arms, we find that the polarization morphology is most consistent with grains aligned through a relative velocity flow between gas and dust in the spiral arms, as envisioned in the recently developed badminton birdie-like alignment mechanism, rather than alignment with a magnetic field or other known alignment mechanisms.
Abstract The majority of stars are born in clustered environments. In these environments, close encounters between young stars with planet-forming disks are expected to occur frequently. However, direct evidence of such interactions remains rare. Here, we report clear signatures of a recent dynamical interaction between the young stellar systems L1448 IRS3A and L1448 IRS3B. Millimeter wavelength observations reveal a distinct, tidally stripped bridge between the two systems. Together with previously reported spiral arm structures at the outer edge of the IRS3A disk and at the inner and outer regions of the IRS3B disk, these features imply that the systems are undergoing a dynamical flyby. Hydrodynamical simulations reproduce these features and suggest that the closest approach occurred about 15,000 yr ago. These findings offer rare insight into how stellar interactions can reshape disk structures and influence the formation of young multiple stellar systems.
Aims. Studying protostellar objects in their earliest stages, particularly during the Class 0 phase, provides key insight into the beginnings of planet formation and dust evolution. Disentangling the various components, such as the envelope, outflow, and nascent disk, to characterize and understand these young systems, however, is particularly challenging. High spatial and spectral resolution observations of molecular line emission with the Atacama Large Millimeter/submillimeter Array (ALMA) are therefore crucial for probing their complex environments. Methods. We present high-resolution (∼30 au) ALMA observations at 1.3 mm of the Class 0 protostellar system IRAS4A2. We analyzed the gas emission surrounding this young source, tracing it from the extended outflow to the most compact inner region and identifying emission lines using the spectral analysis tool CASSIS. Results. We detect large, well-traced outflows in HCN (3–2), H 2 CO (2 12 –1 11 ), and HCO + (3–2), along with numerous complex organic molecules (COMs) such as C 2 H 3 CN, CH 2 (OH)CHO, CH 3 OCHO, and CH 3 C 15 N that trace central, more compact regions. These molecules span upper-energy levels (E u ) ranging from 20 to 487 K and have excitation temperatures between 100 and 300 K. Using moment maps, we analyzed the kinematics and spatial distributions of the molecular emission, revealing a wide range of spatial scales, from compact structures within the IRAS4A2 core at ∼8 au in radius, to extended ∼5000 au outflow emission. Specifically, we find that CH 3 CDO and CH 3 OCHO could both be good tracers of the disk, possibly tracing its rotation. Lines of OCS (22–21), SO 2 (13 3 11 –13 2 12 ), HCN, H 2 CO, and HCO + , which have lower upper-level energies, show more extended structures around IRAS4A2, likely tracing the envelope, disk, accretion shocks, the base of an outflow, and the outflow itself. Some of these molecular lines exhibit signatures consistent with Keplerian rotation, indicating a central protostellar mass of approximately 0.2 M ⊙ . Conclusions. Most COMs appear to trace distinct inner regions near the central protostar, while other molecules like OCS, SO 2 , HCN, and H 2 CO trace more extended structures, such as the envelope or outflows. The kinematics, emission patterns, and position-velocity diagrams suggest that individual molecules trace multiple components simultaneously, making it challenging to disentangle their true origins. Altogether, these findings highlight the complex spatial distribution within the IRAS4A2 system.
We present high-resolution ($\sim$0.05"; 8 au) dust continuum and molecular line observations toward the Class I protostellar system IRAS 04169+2702 in the Taurus B213 region, as part of the ALMA Large Program Early Planet Formation in Embedded Disks (eDisk). The 1.3-mm dust continuum emission traces a circumstellar disk with a central depression toward the protostar. Our VLA observations of the same target reveal a single central peak dominated by the free-free emission, which coincides with the depression of the thermal dust emission. The mean spectral index of the thermal dust emission from 1.3 mm to 1.4 cm is approximately 2.8, suggestive of the presence of grains grown to millimeter or centimeter sizes in the disk. Velocity gradients along the disk major axis are seen in emission from $^{12}$CO (2-1), $^{13}$CO (2-1), and C$^{18}$O (2-1) molecular lines. The position-velocity diagrams of these lines unveil a Keplerian-rotating disk with a radius of $\sim$21 au around a 1.3 $M_{\odot}$ protostar, as well as an infalling and rotating envelope with the angular momentum conserved. In addition to the compact disk, large-scale infalling spiral structures extending up to approximately 1400 au, streamers, are discovered in C$^{18}$O (2-1), SO (6$_5$-5$_4$), and H$_2$CO (3$_{0, 3}$-2$_{0, 2}$) as well as in the 1.3-mm continuum emission. Notably, in the region closer to the protostar, the spatial coincidence of C$^{18}$O and SO may indicate the presence of a shock related to accretion through the spiral arms.
