Characterizing the Protolunar Disk of the Accreting Companion GQ Lupi B*

Abstract GQ Lup B is a young and accreting, substellar companion that appears to drive a spiral arm in the circumstellar disk of its host star. We report high-contrast imaging observations of GQ Lup B with VLT/NACO at 4–5 μm and medium-resolution integral field spectroscopy with VLT/MUSE. The optical spectrum is consistent with an M9 spectral type, shows characteristics of a low-gravity atmosphere, and exhibits strong Hα emission. The H − M′ color is ≳1 mag redder than field dwarfs with similar spectral types, and a detailed analysis of the spectral energy distribution (SED) from optical to mid-infrared wavelengths reveals excess emission in the L′, NB4.05, and M′ bands. The excess flux is well described by a blackbody component with T disk ≈ 460 K and R disk ≈ 65 R J and is expected to trace continuum emission from small grains in a protolunar disk. We derive an extinction of A V ≈ 2.3 mag from the broadband SED with a suspected origin in the vicinity of the companion. We also combine 15 yr of astrometric measurements and constrain the mutual inclination with the circumstellar disk to 84 ± 9 deg, indicating a tumultuous dynamical evolution or a stellar-like formation pathway. From the measured Hα flux and the estimated companion mass, M p ≈ 30 M J, we derive an accretion rate of M ̇ ≈ 10 − 6.5 M J yr − 1 . We speculate that the disk is in a transitional stage in which the assembly of satellites from a pebble reservoir has opened a central cavity while GQ Lup B is in the final stages of its formation.

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High gas-to-dust size ratio indicating efficient radial drift in the mm-faint CX Tauri disk

Astronomy and Astrophysics ◽

10.1051/0004-6361/201935496 ◽

2019 ◽

Vol 626 ◽

pp. L2 ◽

Cited By ~ 16

Author(s):

S. Facchini ◽

E. F. van Dishoeck ◽

C. F. Manara ◽

M. Tazzari ◽

L. Maud ◽

...

Keyword(s):

Near Infrared ◽

Angular Resolution ◽

Spectral Energy Distribution ◽

Theoretical Models ◽

Intensity Profile ◽

Continuum Emission ◽

Spectral Energy ◽

High Angular Resolution ◽

Sharp Drop ◽

Large Program

The large majority of protoplanetary disks have very compact continuum emission (≲15 AU) at millimeter wavelengths. However, high angular resolution observations that resolve these small disks are still lacking, due to their intrinsically fainter emission compared with large bright disks. In this Letter we present 1.3 mm ALMA data of the faint disk (∼10 mJy) orbiting the TTauri star CX Tau at a resolution of ∼40 mas, ∼5 AU in diameter. The millimeter dust disk is compact, with a 68% enclosing flux radius of 14 AU, and the intensity profile exhibits a sharp drop between 10 and 20 AU, and a shallow tail between 20 and 40 AU. No clear signatures of substructure in the dust continuum are observed, down to the same sensitivity level of the DSHARP large program. However, the angular resolution does not allow us to detect substructures on the scale of the disk aspect ratio in the inner regions. The radial intensity profile closely resembles the inner regions of more extended disks imaged at the same resolution in DSHARP, but with no rings present in the outer disk. No inner cavity is detected, even though the disk has been classified as a transition disk from the spectral energy distribution in the near-infrared. The emission of 12CO is much more extended, with a 68% enclosing flux radius of 75 AU. The large difference of the millimeter dust and gas extents (> 5) strongly points to radial drift, and closely matches the predictions of theoretical models.

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Big Three Dragons: A [N ii] 122 μm Constraint and New Dust-continuum Detection of a z = 7.15 Bright Lyman-break Galaxy with ALMA

The Astrophysical Journal ◽

10.3847/1538-4357/ac2a36 ◽

2021 ◽

Vol 923 (1) ◽

pp. 5

Author(s):

Yuma Sugahara ◽

Akio K. Inoue ◽

Takuya Hashimoto ◽

Satoshi Yamanaka ◽

Seiji Fujimoto ◽

...

Keyword(s):

Spectral Energy Distribution ◽

Far Infrared ◽

Abundance Ratio ◽

Continuum Emission ◽

Spectral Energy ◽

High Ionization ◽

The Galaxy ◽

Infrared Spectral ◽

Best Fit ◽

Redshift Galaxies

Abstract We present new Atacama Large Millimeter/submillimeter Array Band 7 observational results of a Lyman-break galaxy at z = 7.15, B14-65666 (“Big Three Dragons”), which is an object detected in [O iii] 88 μm, [C ii] 158 μm, and dust continuum emission during the epoch of reionization. Our targets are the [N ii] 122 μm fine-structure emission line and the underlying 120 μm dust continuum. The dust continuum is detected with a ∼19σ significance. From far-infrared spectral energy distribution sampled at 90, 120, and 160 μm, we obtain a best-fit dust temperature of 40 K (79 K) and an infrared luminosity of log 10 ( L IR / L ⊙ ) = 11.6 (12.1) at the emissivity index β = 2.0 (1.0). The [N ii] 122 μm line is not detected. The 3σ upper limit of the [N ii] luminosity is 8.1 × 107 L ⊙. From the [N ii], [O iii], and [C ii] line luminosities, we use the Cloudy photoionization code to estimate nebular parameters as functions of metallicity. If the metallicity of the galaxy is high (Z > 0.4 Z ⊙), the ionization parameter and hydrogen density are log 10 U ≃ − 2.7 ± 0.1 and n H ≃ 50–250 cm−3, respectively, which are comparable to those measured in low-redshift galaxies. The nitrogen-to-oxygen abundance ratio, N/O, is constrained to be subsolar. At Z < 0.4 Z ⊙, the allowed U drastically increases as the assumed metallicity decreases. For high ionization parameters, the N/O constraint becomes weak. Finally, our Cloudy models predict the location of B14-65666 on the BPT diagram, thereby allowing a comparison with low-redshift galaxies.

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Non-thermal emission and spectral evolution properties of G54.1+0.3

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz1704 ◽

2019 ◽

Vol 487 (4) ◽

pp. 5781-5787

Author(s):

Ji-Yang Ren ◽

Quan-Gui Gao ◽

Huai-Zhen Li ◽

Ju Ma ◽

Shan-Shan Zhao ◽

...

Keyword(s):

Thermal Emission ◽

Spectral Energy Distribution ◽

Photon Emission ◽

Dynamical Evolution ◽

Spectral Energy ◽

Model Parameters ◽

Spectral Evolution ◽

Proton Proton ◽

X Ray ◽

Γ Ray

ABSTRACT The multiband photon emission and spectral evolution of G54.1+0.3 are investigated in the framework of leptonic and leptonic–hadronic models. We model the spectral energy distribution (SED) of the pulsar wind nebula (PWN) and find that both the leptonic and leptonic–hadronic models can well reproduce the multiband observations of the nebula with appropriate model parameters. Combining with dynamical evolution of the PWN, we investigate the time evolution of photon SED and radiative luminosity in the X-ray and TeV γ-ray bands of G54.1+0.3. The results indicate that the synchrotron spectrum and radiative luminosity in the X-ray band of the PWN calculated with these two models have obvious differences as the age increases to about 4 kyr, and the largest difference is present at about 40 kyr. The γ-ray luminosity calculated by the leptonic–hadronic model shows that the contribution of TeV photons arising from the decay of neutral pions produced in proton–proton interaction also changes with time and is always important for modifying the TeV γ-ray spectrum of G54.1+0.3 during the evolution of the PWN.

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Nature of the Dusty S-cluster Object (DSO/G2): Pre-main-sequence star with non-spherical dusty envelope

Proceedings of the International Astronomical Union ◽

10.1017/s1743921316011741 ◽

2016 ◽

Vol 11 (S322) ◽

pp. 231-232

Author(s):

M. Zajaček ◽

M. Valencia-S. ◽

B. Shahzamanian ◽

F. Peissker ◽

A. Eckart ◽

...

Keyword(s):

Energy Distribution ◽

Main Sequence ◽

Near Infrared ◽

Spectral Energy Distribution ◽

Main Sequence Star ◽

Continuum Emission ◽

Spectral Energy ◽

Galactic Centre ◽

Infrared Excess ◽

Sgr A

AbstractNear-infrared observations reveal several infrared-excess sources near the Galactic Centre with emission lines present in their spectra. One of these objects, DSO/G2, which moves around the supermassive black hole (Sgr A*) on a highly eccentric orbit, passed the pericentre at approximately 160 AU in 2014. It remained compact, which implies that at least in this case it is a star embedded in a dusty envelope. The spectral energy distribution and the detection of polarized continuum emission indicate that it is probably a pre-main-sequence star surrounded by a dense envelope with bipolar cavities. In addition, the star associated with DSO/G2 plausibly develops a bow shock due to its supersonic motion. The model of the star surrounded by the non-spherical dusty envelope can reproduce the main characteristics of the DSO/G2 source: 1. spectral energy distribution in near-infrared bands; 2. linear polarization in Ks band; and 3. the overall compact behaviour.

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A multi-wavelength view of magnetic flaring from PMS stars

Astronomy and Astrophysics ◽

10.1051/0004-6361/201833308 ◽

2018 ◽

Vol 620 ◽

pp. A55 ◽

Cited By ~ 7

Author(s):

E. Flaccomio ◽

G. Micela ◽

S. Sciortino ◽

A. M. Cody ◽

M. G. Guarcello ◽

...

Keyword(s):

Spectral Energy Distribution ◽

Circumstellar Disks ◽

Stellar Atmospheres ◽

Spectral Energy ◽

Circumstellar Disk ◽

The Sun ◽

X Rays ◽

X Ray ◽

Multi Wavelength ◽

Pms Stars

Context. Flaring is an ubiquitous manifestation of magnetic activity in low mass stars including, of course, the Sun. Although flares, both from the Sun and from other stars, are most prominently observed in the soft X-ray band, most of the radiated energy is released at optical/UV wavelengths. In spite of decades of investigation, the physics of flares, even solar ones, is not fully understood. Even less is known about magnetic flaring in pre-main sequence (PMS) stars, at least in part because of the lack of suitable multi-wavelength data. This is unfortunate since the energetic radiation from stellar flares, which is routinely observed to be orders of magnitude greater than in solar flares, might have a significant impact on the evolution of circumstellar, planet-forming disks. Aims. We aim at improving our understanding of flares from PMS stars. Our immediate objectives are constraining the relation between flare emission at X-ray, optical, and mid-infrared (mIR) bands, inferring properties of the optically emitting region, and looking for signatures of the interaction between flares and the circumstellar environment, i.e. disks and envelopes. This information might then serve as input for detailed models of the interaction between stellar atmospheres, circumstellar disks and proto-planets. Methods. Observations of a large sample of PMS stars in the NGC 2264 star forming region were obtained in December 2011, simultaneously with three space-borne telescopes, Chandra (X-rays), CoRoT (optical), and Spitzer (mIR), as part of the “Coordinated Synoptic Investigation of NGC 2264” (CSI-NGC 2264). Shorter Chandra and CoRoT observations were also obtained in March 2008. We analyzed the lightcurves obtained during the Chandra observations (∼300 ks and ∼60 ks in 2011 and 2008, respectively), to detect X-ray flares with an optical and/or mIR counterpart. From the three datasets we then estimated basic flare properties, such as emitted energies and peak luminosities. These were then compared to constrain the spectral energy distribution of the flaring emission and the physical conditions of the emitting regions. The properties of flares from stars with and without circumstellar disks were also compared to establish any difference that might be attributed to the presence of disks. Results. Seventy-eight X-ray flares (from 65 stars) with an optical and/or mIR counterpart were detected. The optical emission of flares (both emitted energy and peak flux) is found to correlate well with, and to be significantly larger than, the X-ray emission. The slopes of the correlations suggest that the difference becomes smaller for the most powerful flares. The mIR flare emission seems to be strongly affected by the presence of a circumstellar disk: flares from stars with disks have a stronger mIR emission with respect to stars without disks. This might be attributed to either a cooler temperature of the region emitting both the optical and mIR flux or, perhaps more likely, to the reprocessing of the optical (and X-ray) flare emission by the inner circumstellar disk, providing evidence for flare-induced disk heating.

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CDFS-6664: A Candidate of Lyman-continuum Emission at z ∼ 3.8 Detected by the Hubble Deep UV Legacy Survey

The Astrophysical Journal ◽

10.3847/2041-8213/ac4170 ◽

2021 ◽

Vol 923 (2) ◽

pp. L28

Author(s):

Fang-Ting Yuan ◽

Zhen-Ya Zheng ◽

Ruqiu Lin ◽

Shuairu Zhu ◽

P. T. Rahna

Keyword(s):

Spectral Energy Distribution ◽

Continuum Emission ◽

Spectral Energy ◽

Lyman Break Galaxies ◽

Lyman Continuum ◽

The Galaxy ◽

Average Transmission ◽

Galaxy Center ◽

Deep Uv

Abstract We report the detection of Lyman continuum (LyC) emission from the galaxy, CDFS-6664, at z = 3.797 in a sample of Lyman break galaxies with detected [O iii] emission lines. The LyC emission is detected with a significance ∼5σ in the F336W band of the Hubble Deep UV Legacy Survey, corresponding to the 650–770 Å rest frame. The light centroid of the LyC emission is offset from the galaxy center by about 0.″2 (1.4 pkpc). The Hubble deep images at longer wavelengths show that the emission is unlikely provided by low-redshift interlopers. The photometric and spectroscopic data show that the possible contribution of an active galactic nucleus is quite low. Fitting the spectral energy distribution of this source to stellar population synthesis models, we find that the galaxy is young (∼50 Myr) and actively forming stars with a rate of 52.1 ± 4.9 M ⊙ yr−1. The significant star formation and the spatially offset LyC emission support a scenario where the ionizing photons escape from the low-density cavities in the ISM excavated by massive young stars. From the nebular model, we estimate the escape fraction of LyC photons to be 38% ± 7% and the corresponding intergalactic medium (IGM) transmission to be 60%, which deviates more than 3σ from the average transmission. The unusually high IGM transmission of LyC photons in CDFS-6664 may be related to a foreground type-2 quasar, CDF-202, at z = 3.7, with a projected separation of 1.′2 only. The quasar may have photoevaporated optically thick absorbers and enhance the transmission on the sightline of CDFS-6664.

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Visible and near-infrared spectro-interferometric analysis of the edge-on Be star o Aquarii

Astronomy and Astrophysics ◽

10.1051/0004-6361/201936039 ◽

2020 ◽

Vol 636 ◽

pp. A110 ◽

Cited By ~ 1

Author(s):

E. S. G. de Almeida ◽

A. Meilland ◽

A. Domiciano de Souza ◽

P. Stee ◽

D. Mourard ◽

...

Keyword(s):

Steady State ◽

Near Infrared ◽

Spectral Energy Distribution ◽

Kinematic Model ◽

Spectral Energy ◽

Circumstellar Disk ◽

Be Stars ◽

Rotational Rate ◽

Disk Structure ◽

Be Star

Aims. We present a detailed visible and near-infrared spectro-interferometric analysis of the Be-shell star o Aquarii from quasi-contemporaneous CHARA/VEGA and VLTI/AMBER observations. Methods. We analyzed spectro-interferometric data in the Hα (VEGA) and Brγ (AMBER) lines using models of increasing complexity: simple geometric models, kinematic models, and radiative transfer models computed with the 3D non-LTE code HDUST. Results. We measured the stellar radius of o Aquarii in the visible with a precision of 8%: 4.0 ± 0.3 R⊙. We constrained the circumstellar disk geometry and kinematics using a kinematic model and a MCMC fitting procedure. The emitting disk sizes in the Hα and Brγ lines were found to be similar, at ~10–12 stellar diameters, which is uncommon since most results for Be stars indicate a larger extension in Hα than in Brγ. We found that the inclination angle i derived from Hα is significantly lower (~15°) than the one derived from Brγ: i ~ 61.2° and 75.9°, respectively. While the two lines originate from a similar region of the disk, the disk kinematics were found to be near to the Keplerian rotation (i.e., β = −0.5) in Brγ (β ~ −0.43), but not in Hα (β ~ −0.30). After analyzing all our data using a grid of HDUST models (BeAtlas), we found a common physical description for the circumstellar disk in both lines: a base disk surface density Σ0 = 0.12 g cm−2 and a radial density law exponent m = 3.0. The same kind of discrepancy, as with the kinematic model, is found in the determination of i using the BeAtlas grid. The stellar rotational rate was found to be very close (~96%) to the critical value. Despite being derived purely from the fit to interferometric data, our best-fit HDUST model provides a very reasonable match to non-interferometric observables of o Aquarii: the observed spectral energy distribution, Hα and Brγ line profiles, and polarimetric quantities. Finally, our analysis of multi-epoch Hα profiles and imaging polarimetry indicates that the disk structure has been (globally) stable for at least 20 yr. Conclusions. Looking at the visible continuum and Brγ emission line only, o Aquarii fits in the global scheme of Be stars and their circumstellar disk: a (nearly) Keplerian rotating disk well described by the viscous decretion disk (VDD) model. However, the data in the Hα line shows a substantially different picture that cannot fully be understood using the current generation of physical models of Be star disks. The Be star o Aquarii presents a stable disk (close to the steady-state), but, as in previous analyses, the measured m is lower than the standard value in the VDD model for the steady-state regime (m = 3.5). This suggests that some assumptions of this model should be reconsidered. Also, such long-term disk stability could be understood in terms of the high rotational rate that we measured for this star, the rate being a main source for the mass injection in the disk. Our results on the stellar rotation and disk stability are consistent with results in the literature showing that late-type Be stars are more likely to be fast rotators and have stable disks.

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Self-consistent population spectral synthesis with FADO

Astronomy and Astrophysics ◽

10.1051/0004-6361/201833438 ◽

2019 ◽

Vol 622 ◽

pp. A56 ◽

Cited By ~ 2

Author(s):

Leandro S. M. Cardoso ◽

Jean Michel Gomes ◽

Polychronis Papaderos

Keyword(s):

Star Formation ◽

Galaxy Evolution ◽

Spectral Synthesis ◽

Spectral Energy Distribution ◽

Formation Rate ◽

Continuum Emission ◽

Spectral Energy ◽

Spectral Evolution ◽

Fitting Procedure ◽

Self Consistent

Context. Spectral population synthesis (PS) is a fundamental tool in extragalactic research that aims to decipher the assembly history of galaxies from their spectral energy distribution (SED). Whereas this technique has led to key insights into galaxy evolution in recent decades, star formation histories (SFHs) inferred therefrom have been plagued by considerable uncertainties stemming from inherent degeneracies and the fact that until recently all PS codes were restricted to purely stellar fits, neglecting the essential contribution of nebular emission (ne). With the advent of FADO (Fitting Analysis using Differential evolution Optimisation), the now possible self-consistent modelling of stellar and ne opens new routes to the exploration of galaxy SFHs. Aims. The main goal of this study is to quantitatively explore the accuracy to which FADO can recover physical and evolutionary properties of galaxies and compare its output with that from purely stellar PS codes. Methods. FADO and STARLIGHT were applied to synthetic SEDs that track the spectral evolution of stars and gas in extinction-free mock galaxies of solar metallicity that form their stellar mass (M⋆) according to different parametric SFHs. Spectral fits were computed for two different set-ups that approximate the spectral range of SDSS and CALIFA (V500) data, using up to seven libraries of simple stellar population spectra in the 0.005–2.5 Z⊙ metallicity range. Results. Our analysis indicates that FADO can recover the key physical and evolutionary properties of galaxies, such as M⋆ and mass- and light-weighted mean age and metallicity, with an accuracy better than 0.2 dex. This is the case even in phases of strongly elevated specific star formation rate (sSFR) and thus with considerable ne contamination (EW(Hα) > 103 Å). Likewise, population vectors from FADO adequately recover the mass fraction of stars younger than 10 Myr and older than 1 Gyr (M⋆<10Myr/M⋆total and M⋆>1Gyr/M⋆total, respectively) and reproduce with a high fidelity the observed Hα luminosity. As for STARLIGHT, our analysis documents a moderately good agreement with theoretical values only for evolutionary phases for which ne drops to low levels (EW(Hα) ≤ 60 Å) which, depending on the assumed SFH, correspond to an age between ∼0.1 Gyr and 2–4 Gyr. However, fits with STARLIGHT during phases of high sSFR severely overestimate both M⋆ and the mass-weighted stellar age, whereas strongly underestimate the light-weighted age and metallicity. Furthermore, our analysis suggests a subtle tendency of STARLIGHT to favour a bi-modal SFH, as well a slightly overestimated M⋆<10Myr/M⋆total, regardless of galaxy age. Whereas the amplitude of these biases can be reduced, depending on the specifics of the fitting procedure (e.g. accuracy and completeness of flagging emission lines, omission of the Balmer and Paschen jump from the fit), they persist even in the idealised case of a line-free SED comprising only stellar and nebular continuum emission. Conclusions. The insights from this study suggest that the neglect of nebular continuum emission in STARLIGHT and similar purely stellar PS codes could systematically impact M⋆ and SFH estimates for star-forming galaxies. We argue that these biases can be relevant in the study of a range of topics in extragalactic research, including the redshift-dependent slope of the star formation (SF) main sequence, the SF frosting hypothesis, and the regulatory role of supermassive black holes on the global SFH of galaxies.

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The ALPINE-ALMA [CII] survey

Astronomy and Astrophysics ◽

10.1051/0004-6361/201936965 ◽

2020 ◽

Vol 643 ◽

pp. A1 ◽

Cited By ~ 10

Author(s):

O. Le Fèvre ◽

M. Béthermin ◽

A. Faisst ◽

G. C. Jones ◽

P. Capak ◽

...

Keyword(s):

Detection Rate ◽

Spectral Energy Distribution ◽

Sample Selection ◽

Reference Sample ◽

Far Infrared ◽

Continuum Emission ◽

Spectral Energy ◽

Signal To Noise ◽

Ancillary Data ◽

Wide Range

The ALMA-ALPINE [CII] survey is aimed at characterizing the properties of a sample of normal star-forming galaxies (SFGs). The ALMA Large Program to INvestigate (ALPINE) features 118 galaxies observed in the [CII]-158 μm line and far infrared (FIR) continuum emission during the period of rapid mass assembly, right after the end of the HI reionization, at redshifts of 4 < z < 6. We present the survey science goals, the observational strategy, and the sample selection of the 118 galaxies observed with ALMA, with an average beam minor axis of about 0.85″, or ∼5 kpc at the median redshift of the survey. The properties of the sample are described, including spectroscopic redshifts derived from the UV-rest frame, stellar masses, and star-formation rates obtained from a spectral energy distribution (SED) fitting. The observed properties derived from the ALMA data are presented and discussed in terms of the overall detection rate in [CII] and FIR continuum, with the observed signal-to-noise distribution. The sample is representative of the SFG population in the main sequence at these redshifts. The overall detection rate in [CII] is 64% for a signal-to-noise ratio (S/N) threshold larger than 3.5 corresponding to a 95% purity (40% detection rate for S/N > 5). Based on a visual inspection of the [CII] data cubes together with the large wealth of ancillary data, we find a surprisingly wide range of galaxy types, including 40% that are mergers, 20% extended and dispersion-dominated, 13% compact, and 11% rotating discs, with the remaining 16% too faint to be classified. This diversity indicates that a wide array of physical processes must be at work at this epoch, first and foremost, those of galaxy mergers. This paper sets a reference sample for the gas distribution in normal SFGs at 4 < z < 6, a key epoch in galaxy assembly, which is ideally suited for studies with future facilities, such as the James Webb Space Telescope (JWST) and the Extremely Large Telescopes (ELTs).

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Medium-resolution integral-field spectroscopy for high-contrast exoplanet imaging

Astronomy and Astrophysics ◽

10.1051/0004-6361/201832902 ◽

2018 ◽

Vol 617 ◽

pp. A144 ◽

Cited By ~ 20

Author(s):

H. J. Hoeijmakers ◽

H. Schwarz ◽

I. A. G. Snellen ◽

R. J. de Kok ◽

M. Bonnefoy ◽

...

Keyword(s):

Adaptive Optics ◽

Cross Correlation ◽

High Contrast ◽

Contrast Imaging ◽

Data Set ◽

Stellar Spectrum ◽

High Contrast Imaging ◽

Medium Resolution ◽

Differential Imaging ◽

Integral Field

Context. Angular differential imaging (ADI) and spectral differential imaging (SDI) are well-established high-contrast imaging techniques, but their application is challenging for companions at small angular separations from their host stars. Aims. The aim of this paper is to investigate to what extent adaptive-optics assisted, medium-resolution (R ~ 5000) integral field spectrographs (IFS) can be used to directly detect the absorption of molecular species in the spectra of planets and substellar companions when these are not present in the spectrum of the star. Methods. We analysed archival data of the β Pictoris system taken with the SINFONI integral field spectrograph located at ESO’s Very Large Telescope, originally taken to image β Pictoris b using ADI techniques. At each spatial position in the field, a scaled instance of the stellar spectrum is subtracted from the data after which the residuals are cross-correlated with model spectra. The cross-correlation co-adds the individual absorption lines of the planet emission spectrum constructively, while this is not the case for (residual) telluric and stellar features. Results. Cross-correlation with CO and H2O models results in significant detections of β Pictoris b with signal-to-noise ratios (S/Ns) of 13.7 and 16.4 respectively. Correlation with a T = 1700 K BT-Settl model provides a detection with an S/N of 22.8. This in contrast to application of ADI, which barely reveals the planet. While the adaptive optics system only achieved modest Strehl ratios of 19–27% leading to a raw contrast of 1:240 at the planet position, cross-correlation achieves a 3σ contrast limit of 2.7 × 10−5 in this 2.5 hr data set, a factor ~40 below the raw noise level at an angular distance of 0.36′′ from the star. Conclusions. Adaptive-optics assisted, medium-resolution IFS, such as SINFONI on the VLT and OSIRIS on the Keck Telescope, can be used for high-contrast imaging utilizing cross-correlation techniques for planets that are close to their star and embedded in speckle noise. We refer to this method as molecule mapping, and advocate its application to observations with future medium resolution instruments, in particular ERIS on the VLT, HARMONI on the ELT and NIRSpec, and MIRI on the JWST.

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