arXiv subjects

Frédérick Poidevin

Publications and source records attributed to Frédérick Poidevin.

At least 19 recordsLinked to original sources

arXiv2026

B-fields In STar-forming Region Observations (BISTRO): Technical Foundations for Quantitative 450/850 $μ$m JCMT SCUBA-2/POL-2 Polarimetry

We present five technical validations of SCUBA-2/POL-2 polarimetry on the James Clerk Maxwell Telescope at 450 and 850 $μ$m, using 174 archival fields in 69 molecular cloud regions and subsets appropriate to each test. Extended-source calibration avoids a deterministic shift of $Δβ=-1.05$ in the dust emissivity index $β$ that would result from calibrating extended emission using peak brightness. We modeled Stokes $I$ noise with additive and signal-dependent components. The measured median ratio of surface-brightness noise at 450/850 $μ$m is 25. Independent tests of Stokes $Q,U$ noise support approximately equal additive variances and weak error correlations, providing a basis for propagating polarization uncertainties. Corrections determined for individual fields reduce additive zero-level offsets of order $1$ mJy arcsec$^{-2}$ in the 450 $μ$m Stokes $Q$ and $U$ intensities. The three-step regression leaves a median combined residual amplitude of $0.07$ mJy arcsec$^{-2}$. Independent comparisons with SOFIA/HAWC+ at 154 and 214 $μ$m support the correction in strongly affected fields. We matched the 450 $μ$m maps to the modeled 850 $μ$m beam and the common $12.6''$-$300''$ range of angular scales. We compared three reductions of the same 450 $μ$m observations across 30 sources. Taking the median angular residual relative to the final product for each source, we find that beam matching reduces the median over sources from $6.3^\circ$ to $4.7^\circ$. After matching, 29 of the 30 sources have median residuals below $10^\circ$. We also quantified how residual $Q/U$ offsets propagate in ratios of polarization fractions, differences in spectral indices, and polarization angles. These validations provide procedures and quantitative references for interpreting POL-2 measurements and combining them with polarimetry at other wavelengths.

astro-ph.GA↗

arXiv2026

B-fields In STar-forming Region Observations (BISTRO): Dual-Wavelength Constraints on Size-Dependent Grain Alignment in Star-Forming Regions

We compared 450 and 850 $μ$m POL-2 observations from the James Clerk Maxwell Telescope at $12.6''$ resolution. The median absolute difference in polarization angle between bands is $6.7^\circ$ across 21 regions. For total intensity $I\proptoν^α$ and polarized intensity $PI\proptoν^γ$, 24-27 of 35 regions have $γ<α$, allowing for $3σ$ limits on weak polarized intensities. The median $γ-α$ is $-0.51$, ranging from $-0.57$ to $-0.45$ under these limits. The ratio of polarization fractions is $P_{450}/P_{850}=0.69\pm0.02_{\rm sys}\pm0.03_{\rm stat}$, with no detected dependence on the angle difference. We suggest that the dependence of alignment on grain size offers the simplest explanation of these findings. For optically thin components sharing a polarization angle and opacity law, temperature mixing reproduces the median $-0.51$ only if the warm dust is polarized less efficiently than the cold dust. If the cold dust is at 10 K or warmer and the warm dust at 40 K or cooler, the median requires a ratio of warm to cold effective polarization efficiencies $r\lesssim0.18$. We tested mixtures with opacity index $β=2$ in four fields against Herschel dust temperatures and Green Bank Ammonia Survey kinetic temperatures. We assumed equal gas and dust temperatures, ammonia tracing cold gas, and model ranges of 3-20 K for cold dust and 25-40 K for warm dust carrying at most half the mass. Mixtures matching both temperatures cannot reproduce $γ-α$ within $1σ$ in three fields, including OMC 2 tentatively, even for $r=0$. Allowing warm dust at 10-100 K and up to 95% of the mass permits solutions only for $r\leq0.041$. To explain these three fields by temperature mixing, we need wider model ranges and a very strong contrast in polarization efficiency. The origin of this contrast remains undetermined.

astro-ph.GA↗

arXiv2026

SN 2023iop: An Extreme 1987A-like Supernova and the Death of Very Massive Stars

Supernova (SN) 1987A showed that some hydrogen-rich core-collapse supernovae (SNe) rise slowly to peak, defining a distinct subclass. Wide-field surveys have uncovered more extreme members, such as OGLE-2014-SN-73, SN 2020faa, and SN 2023vbw, that challenge neutrino-driven explosion models. We present ultraviolet-to-infrared, radio, X-ray, and spectropolarimetric observations of SN 2023iop at $z = 0.1020$, the most extreme 87A-like event to date. It rose for $\gtrsim88$ rest-frame days to $M_r \approx -20.1$ mag, also placing it among the hydrogen-rich superluminous SNe, and radiated $\gtrsim4\times10^{50}$ erg. Its spectra resemble those of typical Type II SNe and remain photospheric at $\sim330$ days post-maximum. Continuum polarization of 0.8-1.0% indicates an aspherical system. Hydrogen-rich pair-instability supernova (PISN) models of a $190~M_\odot$ star reproduce the light-curve up to 150 days after peak, but not the late-time emission. A late-time spectrum shows a feature near 7300 Å, tentatively identified as [Ni II] $λ$7378. The implied $\approx0.02~M_\odot$ of stable $^{58}$Ni is reached only in the most massive PISN models. The low-mass host galaxy ($\sim10^{8.2}~M_\odot$) is consistent with a metal-poor progenitor as required by the PISN channel. Fallback accretion reproduces the light-curve morphology, but not the colors. We consider a pair-instability explosion the most plausible scenario, with the late-time light-curve excess powered by circumstellar interaction, which shows no signatures in the spectra. SN 2023iop shows that the most luminous 87A-like events occupy an underexplored region of massive-star evolution.

astro-ph.HE↗

arXiv2026

Early Near-Infrared Excess and Rapid Disk-Corona Evolution in the Tidal Disruption Event 2024aepd

We present multi-wavelength observations of the tidal disruption event (TDE) 2024aepd, spanning primarily the first $\sim$300 days after discovery. A prominent near-infrared (NIR) excess is detected as early as $\sim$40 days. Its nearly flat power-law spectrum strongly deviates from the Rayleigh-Jeans tail of the UV-optical blackbody. Although a conventional dust-echo origin cannot be completely ruled out, free-free emission from a reprocessing photospheric envelope provides a more plausible explanation. The spectral break between the UV-optical and NIR components shifts to higher frequencies, while the inferred density-profile index remains nearly constant, suggesting evolving reprocessing conditions within a broadly unchanged density structure. In addition, the X-ray spectrum is initially dominated by a thermal disk component accompanied by a hard excess. From $\sim$178 days onward, the spectrum becomes power-law dominated and subsequently hardens, indicating the rapid emergence and strengthening of a hot corona. These results provide evidence for frequency-dependent reprocessing at early times and for the rapid development of a disk-corona system, placing new constraints on the structure and evolution of the reprocessing layer around supermassive black holes.

astro-ph.HE↗

arXiv2026

Magnetic field alignment with dense cores in the transition between cloud and core scales

In a magnetically-dominated model of star formation, we expect to see alignments between the magnetic field orientation of star-forming dense cores and the cloud-scale magnetic field. Pandhi et al. (2023) showed instead, however, that the orientation of cores and their angular momentum vectors appear random with respect to the larger-scale magnetic field, implying that magnetic fields may play a diminished role in core formation and evolution. Here, we use higher-resolution dust polarization data from the B-Fields In Star-forming Region Observations (BISTRO) survey on the James Clerk Maxwell Telescope (JCMT) to investigate the change in the magnetic field orientation from cloud scales to core scales, and reassess any correlations between core-scale magnetic fields, core orientations and core velocity gradients. We produce a catalog of 79 cores over 14 star-forming regions with averaged core-scale magnetic field orientations. We find that the core-scale magnetic field is more disordered compared to the cloud-scale field, as measured by an increased standard deviation in the magnetic field vector orientations. Alignment between the core-scale and cloud-scale field varies greatly between regions. Our results are consistent with random alignments between the core-scale magnetic field, core orientation, and core velocity gradient, in agreement with the results by Pandhi et al. (2023) for the cloud-scale field. We conclude that there is a clear change in the magnetic field in the transition from cloud- to core-scales. Our results suggest that the magnetic field may not play a dominant role in the evolution of dense cores on core scales.

astro-ph.GA↗

arXiv2025

SN 2025coe: A Multiple-Peaked Calcium-Strong Transient from A White-Dwarf Progenitor

SN 2025coe is a calcium-strong transient located at an extremely large projected offset $\sim$39.3 kpc from the center of its host, the nearby early-type galaxy NGC 3277 at a distance of $\sim$25.5 Mpc. In this paper, we present multi-band photometric and spectroscopic observations spanning $\sim$100 days post-discovery. Its multi-band light curves display {multiple} distinct peaks: (1) an initial peak at $t \approx 1.6$ days attributed to shock cooling emission, (2) a secondary peak of $M_{R, \, peak} \approx$ $-$15.8 mag at $t \approx 10.2$ days powered by radioactive decay, and (3) a {possible} late-time bump at $t \approx 42.8$ days likely caused by ejecta-circumstellar material/clump interaction. Spectral evolution of SN 2025coe reveals a fast transition to the nebular phase within 2 months, where it exhibits an exceptionally high [Ca II]/[O I] ratio larger than 6. Modeling of the bolometric light curve suggests an ejecta mass of $M_{\rm ej} = 0.29^{+0.14}_{-0.15} \, M_{\odot}$, a $^{56}$Ni mass of $M_{\rm ^{56}Ni} = 2.4^{+0.06}_{-0.05} \times 10^{-2} M_{\odot}$, and a progenitor envelope with mass $M_e = 1.4^{+6.9}_{-1.2} \times 10^{-3} \, M_{\odot}$ and radius $R_e = 13.5^{+64.1}_{-11.1} \, R_{\odot}$. The tidal disruption of a hybrid HeCO white dwarf (WD) by a low-mass CO WD provides a natural explanation for the low ejecta mass, the small fraction of $^{56}$Ni, and the presence of an extended, low-mass envelope.

astro-ph.HE↗

arXiv2025

SN 2023taz: Implications for the UV Diversity of Superluminous Supernovae

Superluminous supernovae (SLSNe) are some of the brightest explosions in the Universe representing the extremes of stellar deaths. At the upper end of their distribution is SN\,2023taz, one of the most luminous SLSNe discovered to date with a peak absolute magnitude of $M_{g,\rm{peak}}=-22.75 \pm 0.03$ and a lower limit for energy radiated of $E=2.9 \times 10^{51}$\,erg. Magnetar model fits reveal individual parameter values typical of the SLSN population, but the combination of a low $B$-field and ejecta mass with a short spin period places SN\,2023taz in a unusual region of parameter space, accounting for its extreme luminosity. The optical data around peak are consistent with a temperature of $\sim$17\,000\,K but SN\,2023taz shows a surprising deficit in the UV compared to other events in this temperature range. We find no indication of dust extinction that could plausibly explain the UV deficit. The lower level of UV flux is reminiscent of the absorption seen in lower-luminosity events like SN\,2017dwh, where Fe-group elements are responsible for the effect. However, in the case of SN\,2023taz, there is no evidence for a larger amount of Fe-group elements which could contribute to line blanketing. Comparing to SLSNe with well-observed UV spectra, an underlying temperature of $8000-9000$\,K would match the UV spectral slope, but is not consistent with the optical colour temperatures of these events. The most likely explanation is enhanced absorption by intermediate-mass elements, challenging previous findings that SLSNe exhibit similar UV absorption line equivalent widths. This highlights the need for expanded UV spectroscopic coverage of SLSNe, especially at early times, to build a framework for interpreting their diversity and to enable classification at higher redshifts where optical observations will exclusively probe rest-frame UV emission.

astro-ph.HE↗

arXiv2025

The JCMT BISTRO-3 Survey: Variation of magnetic field orientations on parsec and sub-parsec scales in the massive star-forming region G28.34+0.06

Magnetic fields play a significant role in star-forming processes on core to clump scales. We investigate magnetic field orientations and strengths in the massive star-forming clump P2 within the filamentary infrared dark cloud G28.34+0.06 using dust polarization observations made using SCUBA-2/POL-2 on the James Clerk Maxwell Telescope as part of the B-field In STar-forming Region Observations (BISTRO) survey. We compare the magnetic field orientations at the clump scale of ~2 parsecs from these JCMT observations with those at the core scale of ~0.2 parsecs from archival ALMA data, finding that the magnetic field orientations on these two different scales are perpendicular to one another. We estimate the distribution of magnetic field strengths, which range from 50 to 430 μG over the clump. The region forming the core shows the highest magnetic field strength. We also obtain the distribution of mass-to-flux ratios across the clump. In the region surrounding the core, the mass-to-flux ratio is larger than 1, which indicates the magnetic field strength is insufficient to support the region against gravitational collapse. Therefore, the change in the magnetic field orientation from clump to core scales may be the result of gravitational collapse, with the field being pulled inward along with the flow of material under gravity.

astro-ph.GA↗

arXiv2025

LensWatch. II. Improved Photometry and Time-delay Constraints on the Strongly Lensed Type Ia Supernova 2022qmx ("SN Zwicky") with HST Template Observations

Strongly lensed supernovae (SNe) are a rare class of transient that can offer tight cosmological constraints that are complementary to methods from other astronomical events. We present a follow-up study of one recently-discovered strongly lensed SN, the quadruply-imaged Type Ia SN 2022qmx (aka, "SN Zwicky") at z = 0.3544. We measure updated, template-subtracted photometry for SN Zwicky and derive improved time delays and magnifications. This is possible because SNe are transient, fading away after reaching their peak brightness. Specifically, we measure point spread function (PSF) photometry for all four images of SN Zwicky in three Hubble Space Telescope WFC3/UVIS passbands (F475W, F625W, F814W) and one WFC3/IR passband (F160W), with template images taken $\sim 11$ months after the epoch in which the SN images appear. We find consistency to within $2σ$ between lens model predicted time delays ($\lesssim1$ day), and measured time delays with HST colors ($\lesssim2$ days), including the uncertainty from chromatic microlensing that may arise from stars in the lensing galaxy. The standardizable nature of SNe Ia allows us to estimate absolute magnifications for the four images, with images A and C being elevated in magnification compared to lens model predictions by about $6σ$ and $3σ$ respectively, confirming previous work. We show that millilensing or differential dust extinction is unable to explain these discrepancies and find evidence for the existence of microlensing in images A, C, and potentially D, that may contribute to the anomalous magnification.

astro-ph.HE↗

arXiv2025

The JCMT BISTRO Survey: Unveiling the Magnetic Fields around Galactic Center

We acquired 450 μm and 850 μm dust continuum polarization observations toward the inner region of the Central Molecular Zone (CMZ) as part of the B-Fields In Star-Forming Region Observations (BISTRO) survey using the POL-2 polarimeter on the James Clerk Maxwell Telescope. These observations encompassed three dense structures: the 20 km s{^{-1}} cloud (20MC), 50 km s{^{-1}} cloud (50MC), and circumnuclear disk (CND). Our aim is to investigate the magnetic field morphology and strength in the inner region of the CMZ using polarized dust continuum and the Davis-Chandrasekhar-Fermi method. The magnetic field morphology is highly ordered in all three dense regions. The plane-of-sky magnetic field strengths are {\sim}1 mG for the 20MC and the 50MC, and {\sim}2 mG for the CND. We compare the energy contributions of turbulence, gravity, and thermal motion with that of the magnetic field using the plasma β, mass-to-flux ratio, and Alfvén Mach number. The outcomes reveal the magnetic field stands out as the predominant factor within the inner region of the CMZ. The dominance of the magnetic field may explain the low star-forming rate in the CMZ. We further investigate the dust grain alignment efficiency by exploring the relationship between polarization fraction and total intensity. The results suggest that dust grains are well aligned with the magnetic fields.

astro-ph.GA↗

arXiv2024

Filamentary Network and Magnetic Field Structures Revealed with BISTRO in the High-Mass Star-Forming Region NGC2264 : Global Properties and Local Magnetogravitational Configurations

We report 850 $μ$m continuum polarization observations toward the filamentary high-mass star-forming region NGC 2264, taken as part of the B-fields In STar forming Regions Observations (BISTRO) large program on the James Clerk Maxwell Telescope (JCMT). These data reveal a well-structured non-uniform magnetic field in the NGC 2264C and 2264D regions with a prevailing orientation around 30 deg from north to east. Field strengths estimates and a virial analysis for the major clumps indicate that NGC 2264C is globally dominated by gravity while in 2264D magnetic, gravitational, and kinetic energies are roughly balanced. We present an analysis scheme that utilizes the locally resolved magnetic field structures, together with the locally measured gravitational vector field and the extracted filamentary network. From this, we infer statistical trends showing that this network consists of two main groups of filaments oriented approximately perpendicular to one another. Additionally, gravity shows one dominating converging direction that is roughly perpendicular to one of the filament orientations, which is suggestive of mass accretion along this direction. Beyond these statistical trends, we identify two types of filaments. The type-I filament is perpendicular to the magnetic field with local gravity transitioning from parallel to perpendicular to the magnetic field from the outside to the filament ridge. The type-II filament is parallel to the magnetic field and local gravity. We interpret these two types of filaments as originating from the competition between radial collapsing, driven by filament self-gravity, and the longitudinal collapsing, driven by the region's global gravity.

astro-ph.SR↗

arXiv2022

JCMT BISTRO Observations: Magnetic Field Morphology of Bubbles Associated with NGC 6334

We study the HII regions associated with the NGC 6334 molecular cloud observed in the sub-millimeter and taken as part of the B-fields In STar-forming Region Observations (BISTRO) Survey. In particular, we investigate the polarization patterns and magnetic field morphologies associated with these HII regions. Through polarization pattern and pressure calculation analyses, several of these bubbles indicate that the gas and magnetic field lines have been pushed away from the bubble, toward an almost tangential (to the bubble) magnetic field morphology. In the densest part of NGC 6334, where the magnetic field morphology is similar to an hourglass, the polarization observations do not exhibit observable impact from HII regions. We detect two nested radial polarization patterns in a bubble to the south of NGC 6334 that correspond to the previously observed bipolar structure in this bubble. Finally, using the results of this study, we present steps (incorporating computer vision; circular Hough Transform) that can be used in future studies to identify bubbles that have physically impacted magnetic field lines.

astro-ph.GA↗

arXiv2021

Progenitor and Close-In Circumstellar Medium of Type II Supernova 2020fqv from High-Cadence Photometry and Ultra-Rapid UV Spectroscopy

We present observations of SN 2020fqv, a Virgo-cluster Type II core-collapse supernova (CCSN) with a high temporal resolution light curve from the Transiting Exoplanet Survey Satellite (TESS) covering the time of explosion; ultraviolet (UV) spectroscopy from the Hubble Space Telescope (HST) starting 3.3 days post-explosion; ground-based spectroscopic observations starting 1.1~days post-explosion; along with extensive photometric observations. Massive stars have complicated mass-loss histories leading up to their death as CCSNe, creating circumstellar medium (CSM) with which the SNe interact. Observations during the first few days post-explosion can provide important information about the mass-loss rate during the late stages of stellar evolution. Model fits to the quasi-bolometric light curve of SN 2020fqv reveal ~0.23 $M_{\odot}$ of CSM confined within ~1450 $R_{\odot}$ ($10^{14}$ cm) from its progenitor star. Early spectra (<4 days post-explosion), both from HST and ground-based observatories, show emission features from high-ionization metal species from the outer, optically thin part of this CSM. We find that the CSM is consistent with an eruption caused by the injection of $\sim$$5\times 10^{46}$ erg into the stellar envelope $\sim$300 days pre-explosion, potentially from a nuclear burning instability at the onset of oxygen burning. Light-curve fitting, nebular spectroscopy, and pre-explosion \textit{HST} imaging consistently point to a red supergiant (RSG) progenitor with $M_{\rm ZAMS}$$\approx$$13.5$--$15 \, M_{\odot}$, typical for SN~II progenitor stars. This finding demonstrates that a typical RSG, like the progenitor of SN 2020fqv, has a complicated mass-loss history immediately before core collapse.

astro-ph.SR↗

arXiv2021

28 -- 40 GHz variability and polarimetry of bright compact sources in the QUIJOTE cosmological fields

We observed 51 sources in the Q-U-I JOint TEnerife (QUIJOTE) cosmological fields which were brighter than 1 Jy at 30 GHz in the Planck Point Source Catalogue (version 1), with the Very Large Array at 28 -- 40 GHz, in order to characterise their high-radio-frequency variability and polarization properties. We find a roughly log-normal distribution of polarization fractions with a median of 2%, in agreement with previous studies, and a median rotation measure (RM) of $\approx$ 1110 rad m$^{-2}$ with one outlier up to $\approx$ 64000 rad m$^{-2}$ which is among the highest RMs measured in quasar cores. We find hints of a correlation between the total intensity flux density and median polarization fraction. We find 59% of sources are variable in total intensity, and 100% in polarization at $3σ$ level, with no apparent correlation between total intensity variability and polarization variability. This indicates that it will be difficult to model these sources without simultaneous polarimetric monitoring observations and they will need to be masked for cosmological analysis.

astro-ph.CO↗

arXiv2019

Thermal emission from the amorphous dust: An alternative possibility of the origin of the anomalous microwave emission

Complete studies of the radiative processes of thermal emission from the amorphous dust from microwave through far infrared wavebands are presented by taking into account, self-consistently for the first time, the standard two-level systems (TLS) model of amorphous materials. The observed spectral energy distributions (SEDs) for the Perseus molecular cloud (MC) and W43 from microwave through far infrared are fitted with the SEDs calculated with the TLS model of amorphous silicate. We have found that the model SEDs well reproduce the observed properties of the anomalous microwave emission (AME). The present result suggests an alternative interpretation for the AME being carried by the resonance emission of the TLS of amorphous materials without introducing new species. Simultaneous fitting of the intensity and polarization SEDs for the Perseus MC and W43 are also performed. The amorphous model reproduces the overall observed feature of the intensity and polarization SEDs of the Perseus MC and W43. However, the model's predicted polarization fraction of the AME is slightly higher than the QUIJOTE upper limits in several frequency bands. A possible improvement of our model to resolve this problem is proposed. Our model predicts that interstellar dust is amorphous materials having very different physical characteristics compared with terrestrial amorphous materials.

astro-ph.GA↗

arXiv2019

Analysis of Galactic molecular cloud polarization maps: a review of the methods

The Davis-Chandrasekhar-Fermi (DCF) method using the Angular Dispersion Function (ADF), the Histogram of Relative Orientations (HROs) and the Polarization-Intensity Gradient Relation (P-IGR) are the most common tools used to analyse maps of linearly polarized emission by thermal dust grains at submilliter wavelengths in molecular clouds and star-forming regions. A short review of these methods is given. The combination of these methods will provide valuable tools to shed light on the impact of the magnetic fields on the formation and evolution of subparsec scale hub-filaments that will be mapped with the NIKA2 camera and future experiments.

astro-ph.IM↗

arXiv2019

Relative Alignment Between the Magnetic Field and Molecular Gas Structure in the Vela C Giant Molecular Cloud using Low and High Density Tracers

We compare the magnetic field orientation for the young giant molecular cloud Vela C inferred from 500-$μ$m polarization maps made with the BLASTPol balloon-borne polarimeter to the orientation of structures in the integrated line emission maps from Mopra observations. Averaging over the entire cloud we find that elongated structures in integrated line-intensity, or zeroth-moment maps, for low density tracers such as $^{12}$CO and $^{13}$CO $J$ $\rightarrow$ 1 - 0 are statistically more likely to align parallel to the magnetic field, while intermediate or high density tracers show (on average) a tendency for alignment perpendicular to the magnetic field. This observation agrees with previous studies of the change in relative orientation with column density in Vela C, and supports a model where the magnetic field is strong enough to have influenced the formation of dense gas structures within Vela C. The transition from parallel to no preferred/perpendicular orientation appears to happen between the densities traced by $^{13}$CO and by C$^{18}$O $J$ $\rightarrow$ 1 - 0. Using RADEX radiative transfer models to estimate the characteristic number density traced by each molecular line we find that the transition occurs at a molecular hydrogen number density of approximately $10^3$ cm$^{-3}$. We also see that the Centre-Ridge (the highest column density and most active star-forming region within Vela C) appears to have a transition at a lower number density, suggesting that this may depend on the evolutionary state of the cloud.

astro-ph.GA↗

arXiv2018

Submillimeter Polarization Spectrum of the Carina Nebula

Linear polarization maps of the Carina Nebula were obtained at 250, 350, and 500 $μ$m during the 2012 flight of the BLASTPol balloon-borne telescope. These measurements are combined with Planck 850 $μ$m data in order to produce a submillimeter spectrum of the polarization fraction of the dust emission, averaged over the cloud. This spectrum is flat to within $\pm$15% (relative to the 350 $μ$m polarization fraction). In particular, there is no evidence for a pronounced minimum of the spectrum near 350 $μ$m, as suggested by previous ground-based measurements of other molecular clouds. This result of a flat polarization spectrum in Carina is consistent with recently-published BLASTPol measurements of the Vela C molecular cloud, and also agrees with a published model for an externally-illuminated, dense molecular cloud by Bethell and collaborators. The shape of the spectrum in Carina does not show any dependence on the radiative environment of the dust, as quantified by the Planck-derived dust temperature or dust optical depth at 353 GHz.

astro-ph.GA↗