About

Hector Arce is an Associate Professor at Yale University, affiliated with the Yale Center for Astronomy and Astrophysics. His office is located in Kline Tower 651. The information provided does not include specific details about his research focus, background, or key contributions.

Research topics

• Astrophysics
• Astronomy
• Physics
• Computer Science
• Optics
• Remote sensing
• Meteorology
• Geology

Selected publications

• The Green Bank Ammonia Survey: Data Release 2

  The Astrophysical Journal Supplement Series · 2026-01-01 · 1 citations

  articleOpen access

  Abstract We present an overview of the final data release (DR2) from the Green Bank Ammonia Survey (GAS). GAS is a large program at the Green Bank Telescope to map all Gould Belt star-forming regions with A V ≳ 7 mag visible from the Northern Hemisphere in emission from NH 3 and other key molecular tracers. This final release includes the data for all the regions observed: Heiles Cloud 2 and B18 in Taurus; Barnard 1, Barnard 1-E, IC 348, NGC 1333, L1448, L1451, and Per7/34 in Perseus; L1688 and L1689 in Ophiuchus; Orion A (North and South) and Orion B in Orion; Cepheus; B59 in Pipe; Corona Australis East and West; IC 5146; and Serpens Aquila and MWC297 in Serpens. Similar to what was presented in GAS DR1, we find that the NH 3 emission and dust continuum emission from Herschel correspond closely. We find that the NH 3 emission is generally extended beyond the typical 0.1 pc length scales of dense cores, and we find that the transition between coherent core and turbulent cloud is a common result. This shows that the regions of coherence are common throughout different star-forming regions, with a substantial fraction of the high column density regions displaying subsonic nonthermal velocity dispersions. We produce maps of the gas kinematics, temperature, and NH 3 column densities through forward modeling of the hyperfine structure of the NH 3 (1,1) and (2,2) lines. We show that the NH 3 velocity dispersion, σ v , and gas kinetic temperature, T K , vary systematically between the regions included in this release, with an increase in both the mean value and spread of σ v and T K with increasing star formation activity. The data presented in this paper are publicly available via doi: 10.11570/24.0091 .

  PublisherDOI

• Protostellar Outflows Shed Light on the Dominant Close Companion Star Formation Pathways

  The Astrophysical Journal · 2026-04-13

  articleOpen access

  Abstract Understanding the formation pathway for close-companion protostars is central to unraveling the processes that govern stellar multiplicity and very early star formation. We analyze a large sample of 51 Class 0/I close-companion protostellar systems, of which 38 show detectable outflows, yielding 42 measured outflows used in our analysis. We use Atacama Large Millimeter/submillimeter Array observations of 11 systems in Perseus and 40 systems in Orion. These companions formed either directly at these small scales (≲500 au separations) via disk fragmentation or at larger scales (>1000 au separations) via turbulent fragmentation followed by inward migration. Because of differences in formation mechanism, the former is expected to have preferentially aligned disks and outflows, whereas the latter is expected to show no preferred alignment. The relative prevalence of these formation pathways remains uncertain, yet it is critical to forming a comprehensive picture of star formation. We examine the distribution of position angles (PAs) of companion protostars relative to the PAs of their molecular outflows. The outflow, as traced by 12 CO ( J = 2 → 1), is a useful proxy for the angular momentum of the system, expected to be orthogonal to the binary orbital plane. We use a simple model to account for a random sampling of inclination and orbital phase in each system, finding that the observations are consistent with a distribution where the outflows are preferentially orthogonal to the companions. Based on this analysis, we suggest disk fragmentation is the dominant formation pathway for close-companion protostellar systems.

  PublisherDOI

• Protostellar Outflows Shed Light on the Dominant Close Companion Star Formation Pathways

  arXiv (Cornell University) · 2026-03-02

  preprintOpen access

  Understanding the formation pathway for close-companion protostars is central to unraveling the processes that govern stellar multiplicity and very early star formation. We analyze a large sample of 51 Class 0/I close-companion protostellar systems, of which 38 show detectable outflows, yielding 42 measured outflows used in our analysis. We use ALMA observations of 11 systems in Perseus and 40 systems in Orion. These companions formed either directly at these small scales ($\lesssim 500$ au separations) via disk fragmentation or at larger scales ($> 1000$ au separations) via turbulent fragmentation followed by inward migration. Because of differences in formation mechanism, the former is expected to have preferentially aligned disks and outflows, whereas the latter is expected to show no preferred alignment. The relative prevalence of these formation pathways remains uncertain, yet it is critical to forming a comprehensive picture of star formation. We examine the distribution of position angles of companion protostars relative to the position angles of their molecular outflows. The outflow, as traced by $^{12}$CO ($J=2\rightarrow1$), is a useful proxy for the angular momentum of the system, expected to be orthogonal to the binary orbital plane. We use a simple model to account for random sampling of inclination and orbital phase in each system, finding that the observations are consistent with a distribution in which the outflows are preferentially orthogonal to the companions. Based on this analysis, we suggest disk fragmentation is the dominant formation pathway for close-companion protostellar systems.

  PublisherDOI

• HH 270/110 as a jet/shear layer interaction

  ArXiv.org · 2025-01-22

  preprintOpen access

  New observations obtained with JWST of the proto-stellar HH~270 jet and the "deflected" HH 110 system, show that HH 110 has a morphology of a series of distorted working surfaces. These working surfaces appear to be "deflected versions" of the heads of the incident, HH 270 jet. We compute a series of 3D numerical simulations, in which we explore the possible parameters of a shearing environment that could give origin to the deflection of HH 270 into the HH 110 flow. We find that we need a quite high sideways velocity for the streaming environment (of ~30km/s) in order to produce the complex structure observed in HH 110. This high velocity would be possible in an environment which has been strongly perturbed by the passage of other outflows.

  PublisherOA PDFDOI

• HH 270/110 as a Jet/Shear Layer Interaction

  The Astrophysical Journal · 2025-02-28 · 3 citations

  articleOpen access

  Abstract New observations obtained with JWST of the protostellar HH 270 jet and the “deflected” HH 110 system show that HH 110 has a morphology of a series of distorted working surfaces. These working surfaces appear to be “deflected versions” of the heads of the incident HH 270 jet. We compute a series of 3D numerical simulations, in which we explore the possible parameters of a shearing environment that could give rise to the deflection of HH 270 into the HH 110 flow. We find that we need quite a high sideways velocity for the streaming environment (∼30 km s −1 ) in order to produce the complex structure observed in HH 110. This high velocity would be possible in an environment that has been strongly perturbed by the passage of other outflows.

  PublisherDOI

• PROJECT-J: The Shocking H ₂ Outflow from HH 46

  The Astrophysical Journal · 2025-12-16 · 3 citations

  articleOpen accessCorresponding

  Abstract We analyze the H 2 emission observed in the HH 46 Class I system as part of PROtostellar JEts Cradle Tested with JWST (PROJECT-J), to investigate the origin and excitation of the warm molecular outflow. We used NIRSpec and MIRI spectral maps (1.6–27.9 μ m) to trace the structure and physical conditions of the outflow. By fitting the H 2 rotational diagrams with a multitemperature gas model, we derived key physical parameters, including temperature, extinction, column densities, and the ortho-to-para ratio. This information is combined with a detailed kinematical analysis and comparison with irradiated shock models. We find no evidence of H 2 temperature or velocity stratification from the axis to the edge of the outflow, as would be expected in MHD disk-wind models and as observed in other outflows. Instead, the observations suggest that the H 2 emission arises from shock interactions of jet bow shocks and/or wide-angle winds with the ambient medium and cavity walls. NIRSpec emission and velocity maps reveal expanding molecular shells, likely driven by the less luminous source in the binary system. We infer an accretion rate of ≲10 −9 M ⊙ yr −1 for the secondary source, approximately one order of magnitude lower than that of the primary. The H 2 emission is consistent with excitation by low-velocity (∼10 km s −1 ) J-type shocks, irradiated by an external UV field that may originate from strong dissociative shocks driven by the atomic jet. Future JWST observations will further constrain the evolution of the expanding shell and the mechanisms driving the outflow.

  PublisherDOI

• CAMPOS

  Astronomy and Astrophysics · 2025-07-21 · 6 citations

  articleOpen access

  The 1.3 mm CAMPOS survey has resolved 90 protostellar disks with ~15 au resolution across the Ophiuchus, Corona Australis, and Chamaeleon star-forming regions. To address the fundamental question of when planet formation begins, we combined the CAMPOS sample with literature observations of Class 0-II disks (bolometric temperature, T bol ≤ 1900 K), all mapped at 1.3 mm with resolutions ranging from 4 to 33 au. To investigate substructure detection rates as a function of bolometric temperature, we restricted the sample to disks observed at a wavelength of 1.3 mm, with inclinations below 75° and linear resolutions ≤20 au, and resolved with at least four resolution elements (θ disk /θ res ≥ 4). We also considered the effects of extinction correction and the inclusion of Herschel Space Telescope data on the bolometric temperature measurements to constrain the lower and upper limits of bolometric temperature for each source. We find that by T bol ~ 200-400 K, substructure detection rates increase sharply to ~60%, corresponding to an approximate age of 0.2–0.4 Myr. No substructures are detected in Class 0 disks. The ratio of disk-averaged brightness temperature to predicted dust temperature shows a trend of increasing values toward the youngest Class 0 disks, suggesting higher optical depths in these early stages. Our statistical analysis confirms that substructures similar to the ones in Class II disks are already common by the Class I stage, and the emergence of these structures at T bol ~ 200-400 K could represent only an upper limit. Classifying disks with substructures into those with and without large central cavities, we find both populations coexisting across evolutionary stages, suggesting that they are not necessarily evolutionarily linked. Suppose protostellar disk substructures do follow an evolutionary sequence. In that case, our results imply that disk substructures evolve very rapidly and thus can be present in all Class I/II stages and/or that they can be triggered at different times.

  PublisherDOI

• The Protostars in Orion: Characterizing the Properties of Their Magnetized Envelopes

  The Astrophysical Journal · 2025-02-24 · 4 citations

  articleOpen access

  Abstract We present a study connecting the physical properties of protostellar envelopes to the morphology of the envelope-scale magnetic field. We used the Atacama Large Millimeter/submillimeter Array (ALMA) polarization observations of 61 young protostars at 0.87 mm on ~400–3000 au scales from the B -field Orion Protostellar Survey to infer the envelope-scale magnetic field, and we used the dust emission to measure the envelope properties on comparable scales. We find that protostars showing standard hourglass magnetic field morphology tend to have larger masses, and the nonthermal velocity dispersion is positively correlated with the bolometric luminosity and dust temperature of the envelope. Combining with the disk properties taken from the Orion VLA/ALMA Nascent Disk and Multiplicity survey, we connect envelope properties to fragmentation. Our results show a positive correlation between the fragmentation level and the angle dispersion of the magnetic field, suggesting that the envelope fragmentation tends to be suppressed by the magnetic field. We also find that protostars exhibiting standard hourglass magnetic field structure tend to have a smaller disk and smaller angle dispersion of the magnetic field than other field configurations, especially the rotated hourglass, but also the spiral and others, suggesting a more effective magnetic braking in the standard hourglass morphology of magnetic fields. Nevertheless, significant misalignment between the magnetic field and outflow axes tends to reduce magnetic braking, leading to the formation of larger disks.

  PublisherDOI

• On the Magnetic Field Properties of Protostellar Envelopes in Orion

  The Astrophysical Journal Letters · 2024-02-29 · 18 citations

  preprintOpen access

  Abstract We present 870 μ m polarimetric observations toward 61 protostars in the Orion molecular clouds with ∼400 au (1″) resolution using the Atacama Large Millimeter/submillimeter Array. We successfully detect dust polarization and outflow emission in 56 protostars; in 16 of them the polarization is likely produced by self-scattering. Self-scattering signatures are seen in several Class 0 sources, suggesting that grain growth appears to be significant in disks at earlier protostellar phases. For the rest of the protostars, the dust polarization traces the magnetic field, whose morphology can be approximately classified into three categories: standard-hourglass, rotated-hourglass (with its axis perpendicular to outflow), and spiral-like morphology. A total of 40.0% (±3.0%) of the protostars exhibit a mean magnetic field direction approximately perpendicular to the outflow on several × 10 2 –10 3 au scales. However, in the remaining sample, this relative orientation appears to be random, probably due to the complex set of morphologies observed. Furthermore, we classify the protostars into three types based on the C 17 O (3–2) velocity envelope’s gradient: perpendicular to outflow, nonperpendicular to outflow, and unresolved gradient (≲1.0 km s −1 arcsec −1 ). In protostars with a velocity gradient perpendicular to outflow, the magnetic field lines are preferentially perpendicular to outflow, with most of them exhibiting a rotated hourglass morphology, suggesting that the magnetic field has been overwhelmed by gravity and angular momentum. Spiral-like magnetic fields are associated with envelopes having large velocity gradients, indicating that the rotation motions are strong enough to twist the field lines. All of the protostars with a standard-hourglass field morphology show no significant velocity gradient due to the strong magnetic braking.

  PublisherOA PDFDOI

• PROJECT-J: JWST observations of HH46~IRS and its outflow. Overview and first results

  arXiv (Cornell University) · 2024-04-10

  preprintOpen access

  We present the first results of the JWST program PROJECT-J (PROtostellar JEts Cradle Tested with JWST ), designed to study the Class I source HH46 IRS and its outflow through NIRSpec and MIRI spectroscopy (1.66 to 28 micron). The data provide line-images (~ 6.6" in length with NIRSpec, and up to 20" with MIRI) revealing unprecedented details within the jet, the molecular outflow and the cavity. We detect, for the first time, the red-shifted jet within ~ 90 au from the source. Dozens of shock-excited forbidden lines are observed, including highly ionized species such as [Ne III] 15.5 micron, suggesting that the gas is excited by high velocity (> 80 km/s) shocks in a relatively high density medium. Images of H2 lines at different excitations outline a complex molecular flow, where a bright cavity, molecular shells, and a jet-driven bow-shock interact with and are shaped by the ambient conditions. Additional NIRCam 2 micron images resolve the HH46 IRS ~ 110 au binary system and suggest that the large asymmetries observed between the jet and the H2 wide angle emission could be due to two separate outflows being driven by the two sources. The spectra of the unresolved binary show deep ice bands and plenty of gaseous lines in absorption, likely originating in a cold envelope or disk. In conclusion, JWST has unraveled for the first time the origin of the HH46 IRS complex outflow demonstrating its capability to investigate embedded regions around young stars, which remain elusive even at near-IR wavelengths.

  PublisherOA PDFDOI

Recent grants

• CAREER: Star Formation and Dense Gas Dynamics in Molecular Clouds

  NSF · $750k · 2009–2014

• The Impact of Young Stellar Outflows on their Surroundings

  NSF · $201k · 2004–2007

• Jets from Young Stars and Their Impact on Star Formation

  NSF · $364k · 2017–2023

Frequent coauthors

• Alyssa Goodman

  Center for Astrophysics Harvard & Smithsonian

  69 shared

• Michael M. Dunham

  64 shared

• J. E. Pineda

  57 shared

• John Tobin

  44 shared

• Stella S. R. Offner

  43 shared

• Manuel Fernández-López

  Consejo Nacional de Investigaciones Científicas y Técnicas

  43 shared

• Tyler L. Bourke

  41 shared

• Shuo Kong

  34 shared