scholarly journals Accretion and Outflow Activity in the Earliest Phases of Star-Formation: CO, Sub-mm Continuum, and Near-Infrared Observations

1997 ◽  
Vol 163 ◽  
pp. 725-726
Author(s):  
K.-W. Hodapp ◽  
E. F. Ladd
Keyword(s):  
Near Infrared ◽  
Spectral Energy Distribution ◽  
Far Infrared ◽  
Point Sources ◽  
Spectral Energy ◽  
Infrared Observations ◽  
Circumstellar Material ◽  
Dense Cores ◽  
Wavelength Radiation ◽  
Main Component

Stars in the earliest phases of their formation, i.e., those accreting the main component of their final mass, are deeply embedded within dense cores of dust and molecular material. Because of the high line-of-sight extinction and the large amount of circumstellar material, stellar emission is reprocessed by dust into long wavelength radiation, typically in the far-infrared and sub-millimeter bands. Consequently, the youngest sources are strong submillimeter continuum sources, and often undetectable as point sources in the near-infrared and optical. The most deeply embedded of these sources have been labelled “Class 0” sources by André, Ward-Thompson, & Barsony (1994), in an extension of the spectral energy distribution classification scheme first proposed by Adams, Lada, & Shu (1987).

scholarly journals Multiple dust shells around Herbig Ae/Be stars

1987 ◽  
Vol 122 ◽  
pp. 99-100
Author(s):  
P.S. Thé ◽  
D. N. Dawanas
Keyword(s):  
Main Sequence ◽  
Near Infrared ◽  
Spectral Energy Distribution ◽  
Far Infrared ◽  
Central Star ◽  
Spectral Energy ◽  
Be Stars ◽  
Intermediate Mass ◽  
Dust Shells ◽  
Average Size

Intermediate mass (2 < M/M⊙ < 9) pre-main sequence objects, also named Herbig Ae/Be stars, are known to have excess radiation in the near-infrared. From IRAS o bservations it turns out without doubt (quality 3, high S/N radio), that these objects are very strong far-infrared emitters at 12, 25, 60 and often also at 100 μm. The spectral energy distribution, depicted in Fig. 1 for intermediate mass pre-main sequence stars, show clearly this large excess. From the difference curves it is apparent that this excess radiation is most probably caused by several dust shells. Using very simplified methods it is possible to derive the average temperature of the dust shells (see Thé, Wesselius, Tjin A Djie and Steenman, 1986). If the chemical composition of the mixture of the dust grains and their average size are assumed it is also possible to estimate other characteristics like the distance from the central star and the mass of the dust shells (see Thé, Hageman, Westerlund, Tjin A Djie, 1985).

scholarly journals The polarized spectral energy distribution of NGC 4151

2020 ◽  
Vol 496 (1) ◽  
pp. 215-222
Author(s):  
F Marin ◽  
J Le Cam ◽  
E Lopez-Rodriguez ◽  
M Kolehmainen ◽  
B L Babler ◽  
...  
Keyword(s):  
Near Infrared ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
Far Infrared ◽  
Seyfert Galaxies ◽  
Mie Scattering ◽  
Polarization Measurement ◽  
Spectral Energy ◽  
Ngc 4151 ◽  
Near Ir

ABSTRACT NGC 4151 is among the most well-studied Seyfert galaxies that does not suffer from strong obscuration along the observer’s line of sight. This allows to probe the central active galactic nucleus (AGN) engine with photometry, spectroscopy, reverberation mapping, or interferometry. Yet, the broad-band polarization from NGC 4151 has been poorly examined in the past despite the fact that polarimetry gives us a much cleaner view of the AGN physics than photometry or spectroscopy alone. In this paper, we compile the 0.15–89.0 μm total and polarized fluxes of NGC 4151 from archival and new data in order to examine the physical processes at work in the heart of this AGN. We demonstrate that, from the optical to the near-infrared (IR) band, the polarized spectrum of NGC 4151 shows a much bluer power-law spectral index than that of the total flux, corroborating the presence of an optically thick, locally heated accretion flow, at least in its near-IR emitting radii. Specific signatures from the atmosphere of the accretion structure are tentatively found at the shortest ultraviolet (UV) wavelengths, before the onset of absorption opacity. Otherwise, dust scattering appears to be the dominant contributor from the near-UV to near-IR polarized spectrum, superimposed on to a weaker electron component. We also identify a change in the polarization processes from the near-IR to the mid-IR, most likely associated with the transition from Mie scattering to dichroic absorption from aligned dust grains in the dusty torus or narrow-line region. Finally, we present and discuss the very first far-infrared polarization measurement of NGC 4151 at 89 μm.

scholarly journals Revealing the Nature of the Highly Obscured Galactic Source IGR J16318-4848

2004 ◽  
Vol 194 ◽  
pp. 65-66
Author(s):  
S. Chaty ◽  
P. Filliatre
Keyword(s):  
Near Infrared ◽  
Spectral Energy Distribution ◽  
Nir Spectroscopy ◽  
High Mass ◽  
Spectral Energy ◽  
X Ray ◽  
Circumstellar Material ◽  
New Class ◽  
Galactic Source ◽  
Early Type Star

AbstractThe X-ray source IGR J16318-4848 was the first source discovered by INTEGRAL on 2003, January 29. We carried out optical and near-infrared (NIR) observations at the European Southern Observatory (ESO La Silla) in the course of a Target of Opportunity (ToO) programme. We discovered the optical counterpart and confirmed an already proposed NIR candidate. NIR spectroscopy revealed a large amount of emission lines, including forbidden iron lines and P-Cygni profiles. The spectral energy distribution of the source points towards a high luminosity and a high temperature, with an absorption greater than the interstellar absorption, but two orders of magnitude lower than the X-ray absorption. We show that the source is an High Mass X-ray binary (HMXB) at a distance between ~ 1 and ~ 6 kpc, the mass donor being an early-type star, probably a sgB[e] star, surrounded by a rich and absorbing circumstellar material. This would make the second High Mass X-ray Binary (HMXB) with a sgB[e] star after CI Cam, indicating that a new class of strongly absorbed X-ray binaries is being unveiled by INTEGRAL.

scholarly journals HELP: a catalogue of 170 million objects, selected at 0.36–4.5 μm, from 1270 deg2 of prime extragalactic fields

2019 ◽  
Vol 490 (1) ◽  
pp. 634-656 ◽  
Author(s):  
Raphael Shirley ◽  
Yannick Roehlly ◽  
Peter D Hurley ◽  
Veronique Buat ◽  
María del Carmen Campos Varillas ◽  
...  
Keyword(s):  
Near Infrared ◽  
Spectral Energy Distribution ◽  
Value Added ◽  
Far Infrared ◽  
Spectral Energy ◽  
Distribution Modelling ◽  
Sigma Point ◽  
Photometric Redshift ◽  
First Time ◽  
Cross Match

ABSTRACT We present an optical to near-infrared (NIR) selected astronomical catalogue covering 1270 deg2. This is the first attempt to systematically combine data from 23 of the premier extragalactic survey fields – the product of a vast investment of telescope time. The fields are those imaged by the Herschel Space Observatory that form the Herschel Extragalactic Legacy Project (HELP). Our catalogue of 170 million objects is constructed by a positional cross-match of 51 public surveys. This high-resolution optical, NIR, and mid-infrared catalogue is designed for photometric redshift estimation, extraction of fluxes in lower resolution far-infrared maps, and spectral energy distribution modelling. It collates, standardizes, and provides value added derived quantities including corrected aperture magnitudes and astrometry correction over the Herschel extragalactic wide fields for the first time. $grizy$ fluxes are available on all fields with g-band data reaching $5\sigma$ point-source depths in a 2 arcsec aperture of 23.5, 24.4, and 24.6 (AB) mag at the 25th, 50th, and 75th percentiles, by area covered, across all HELP fields. It has K or $K_s$ coverage over 1146 deg2 with depth percentiles of 20.2, 20.4, and 21.0 mag, respectively. The IRAC Ch 1 band is available over 273 deg2 with depth percentiles of 17.7, 21.4, and 22.2 mag, respectively. This paper defines the ‘masterlist’ objects for the first data release (DR1) of HELP. This large sample of standardized total and corrected aperture fluxes, uniform quality flags, and completeness measures provides large well-understood statistical samples over the full Herschel extragalactic sky.

scholarly journals Predicting the global far-infrared SED of galaxies via machine learning techniques

2020 ◽  
Vol 634 ◽  
pp. A57 ◽  
Author(s):  
W. Dobbels ◽  
M. Baes ◽  
S. Viaene ◽  
S. Bianchi ◽  
J. I. Davies ◽  
...  
Keyword(s):  
Machine Learning ◽  
Energy Balance ◽  
Near Infrared ◽  
Spectral Energy Distribution ◽  
Far Infrared ◽  
Space Mission ◽  
Machine Learning Techniques ◽  
Spectral Energy ◽  
Learning Framework ◽  
Learning Techniques

Context. Dust plays an important role in shaping a galaxy’s spectral energy distribution (SED). It absorbs ultraviolet (UV) to near-infrared radiation and re-emits this energy in the far-infrared (FIR). The FIR is essential to understand dust in galaxies. However, deep FIR observations require a space mission, none of which are still active today. Aims. We aim to infer the FIR emission across six Herschel bands, along with dust luminosity, mass, and effective temperature, based on the available UV to mid-infrared (MIR) observations. We also want to estimate the uncertainties of these predictions, compare our method to energy balance SED fitting, and determine possible limitations of the model. Methods. We propose a machine learning framework to predict the FIR fluxes from 14 UV–MIR broadband fluxes. We used a low redshift sample by combining DustPedia and H-ATLAS, and extracted Bayesian flux posteriors through SED fitting. We trained shallow neural networks to predict the far-infrared fluxes, uncertainties, and dust properties. We evaluated them on a test set using a root mean square error (RMSE) in log-space. Results. Our results (RMSE = 0.19 dex) significantly outperform UV–MIR energy balance SED fitting (RMSE = 0.38 dex), and are inherently unbiased. We can identify when the predictions are off, for example when the input has large uncertainties on WISE 22 μm, or when the input does not resemble the training set. Conclusions. The galaxies for which we have UV–FIR observations can be used as a blueprint for galaxies that lack FIR data. This results in a “virtual FIR telescope”, which can be applied to large optical-MIR galaxy samples. This helps bridge the gap until the next FIR mission.

scholarly journals The Formation of Massive Stars: from Herschel to Near-Infrared

2014 ◽  
Vol 1 (1) ◽  
pp. 103-107
Author(s):  
Paolo Persi ◽  
Mauricio Tapia
Keyword(s):  
Near Infrared ◽  
Narrow Band ◽  
Narrow Band Imaging ◽  
Spectral Energy Distribution ◽  
Far Infrared ◽  
High Mass ◽  
Spectral Energy ◽  
Mass Star ◽  
Stellar Cluster ◽  
Star Forming

We have studied a number of selected high mass star forming regions, including high resolution near-infrared broad- and narrow-band imaging, Herschel (70, 160, 250, 350 and 500<em> μ</em>m) and Spitzer (3.6, 4.5, 5.8 and 8.0 m) images. The preliminary results of one of this region, IRAS 19388+2357(MOL110) are discussed. In this region a dense core has been detected in the far-infrared, and a young stellar cluster has been found around this core. Combining near-IR data with Spitzer and Herschel photometry we have derived the spectral energy distribution of Mol110. Finally comparing our H<sub>2</sub> and Kc narrow-band images, we have found an H<sub>2</sub> jet in this region.

scholarly journals Optical and Near Infrared Observations of Post-AGB Stars

1998 ◽  
Vol 11 (1) ◽  
pp. 383-383
Author(s):  
T. Fujii ◽  
T. Ono ◽  
Y. Nakada ◽  
M. Parthasarathy
Keyword(s):  
Near Infrared ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
Asymptotic Giant Branch ◽  
Spectral Energy ◽  
Agb Stars ◽  
Ir Camera ◽  
Infrared Observations ◽  
Infrared Wavelengths ◽  
Band Spectra

The post-AGB stars rapidly change their spectral energy distribution on their way from the asymptotic giant branch(AGB) to planetary nebula stage. They are generally surrounded by cool and extended dust shells emitting largely in the infrared wavelengths. A selected sample of the post-AGB candidates were observed using the CCDand IR camera at Kiso and Nishi-Harima Astronomical Observatory. They were classified based on their broad band spectra from B to K’ band and their evolutionary stages have been discussed using the simple model of the dust shell around a star. The light variation of some of these objects were monitored and their light curves are also presented.

scholarly journals UVIT-HST-Gaia-VISTA study of KRON 3 in the Small Magellanic Cloud: A cluster with an extended red clump in UV

2021 ◽  
Author(s):  
P K Nayak ◽  
A Subramaniam ◽  
S Subramanian ◽  
S Sahu ◽  
C Mondal ◽  
...  
Keyword(s):  
Near Infrared ◽  
Spectral Energy Distribution ◽  
Variable Mass ◽  
Intrinsic Property ◽  
Small Variation ◽  
Magellanic Cloud ◽  
Spectral Energy ◽  
Small Range ◽  
Small Magellanic Cloud ◽  
Red Clump

Abstract We have demonstrated the advantage of combining multi-wavelength observations, from the ultraviolet (UV) to near-infrared, to study Kron 3, a massive star cluster in the Small Magellanic Cloud. We have estimated the radius of the cluster Kron 3 to be 2${_{.}^{\prime}}$0 and for the first time, we report the identification of NUV-bright red clump (RC) stars and the extension of the RC in colour and magnitude in the NUV versus (NUV−optical) colour-magnitude diagram (CMD). We found that extension of the RC is an intrinsic property of the cluster and it is not due to contamination of field stars or differential reddening across the field. We studied the spectral energy distribution of the RC stars, and estimated a small range in temperature ∼5000–5500 K, luminosity ∼60–90 L⊙ and radius ∼8.0–11.0 R⊙ supporting their RC nature. The range of UV magnitudes amongst the RC stars (∼23.3 to 24.8 mag) is likely caused by the combined effects of variable mass loss, variation in initial helium abundance (Yini = 0.23 to 0.28), and a small variation in age (6.5-7.5 Gyr) and metallicity ([Fe/H] = −1.5 to −1.3). Spectroscopic follow-up observations of RC stars in Kron 3 are necessary to confirm the cause of the extended RC.

scholarly journals Towards a census of high-redshift dusty galaxies with Herschel

2018 ◽  
Vol 614 ◽  
pp. A33 ◽  
Author(s):  
D. Donevski ◽  
V. Buat ◽  
F. Boone ◽  
C. Pappalardo ◽  
M. Bethermin ◽  
...  
Keyword(s):  
Galaxy Evolution ◽  
High Redshift ◽  
Spectral Energy Distribution ◽  
Formation Rate ◽  
Far Infrared ◽  
Virgo Cluster ◽  
Spectral Energy ◽  
Distribution Fitting ◽  
Redshift Distribution ◽  
Star Forming

Context. Over the last decade a large number of dusty star-forming galaxies has been discovered up to redshift z = 2 − 3 and recent studies have attempted to push the highly confused Herschel SPIRE surveys beyond that distance. To search for z ≥ 4 galaxies they often consider the sources with fluxes rising from 250 μm to 500 μm (so-called “500 μm-risers”). Herschel surveys offer a unique opportunity to efficiently select a large number of these rare objects, and thus gain insight into the prodigious star-forming activity that takes place in the very distant Universe. Aims. We aim to implement a novel method to obtain a statistical sample of 500 μm-risers and fully evaluate our selection inspecting different models of galaxy evolution. Methods. We consider one of the largest and deepest Herschel surveys, the Herschel Virgo Cluster Survey. We develop a novel selection algorithm which links the source extraction and spectral energy distribution fitting. To fully quantify selection biases we make end-to-end simulations including clustering and lensing. Results. We select 133 500 μm-risers over 55 deg2, imposing the criteria: S500 > S350 > S250, S250 > 13.2 mJy and S500 > 30 mJy. Differential number counts are in fairly good agreement with models, displaying a better match than other existing samples. The estimated fraction of strongly lensed sources is 24+6-5% based on models. Conclusions. We present the faintest sample of 500 μm-risers down to S250 = 13.2 mJy. We show that noise and strong lensing have an important impact on measured counts and redshift distribution of selected sources. We estimate the flux-corrected star formation rate density at 4 < z < 5 with the 500 μm-risers and find it to be close to the total value measured in far-infrared. This indicates that colour selection is not a limiting effect to search for the most massive, dusty z > 4 sources.

scholarly journals Orbital and atmospheric characterization of the planet within the gap of the PDS 70 transition disk

2018 ◽  
Vol 617 ◽  
pp. L2 ◽  
Author(s):  
A. Müller ◽  
M. Keppler ◽  
Th. Henning ◽  
M. Samland ◽  
G. Chauvin ◽  
...  
Keyword(s):  
Adaptive Optics ◽  
Near Infrared ◽  
Direct Detection ◽  
Spectral Energy Distribution ◽  
Spectral Energy ◽  
Infrared Range ◽  
Data Set ◽  
Cloud Properties ◽  
Spectrophotometric Data ◽  
First Time

Context. The observation of planets in their formation stage is a crucial but very challenging step in understanding when, how, and where planets form. PDS 70 is a young pre-main sequence star surrounded by a transition disk, in the gap of which a planetary-mass companion has recently been discovered. This discovery represents the first robust direct detection of such a young planet, possibly still at the stage of formation. Aims. We aim to characterize the orbital and atmospheric properties of PDS 70 b, which was first identified on May 2015 in the course of the SHINE survey with SPHERE, the extreme adaptive-optics instrument at the VLT. Methods. We obtained new deep SPHERE/IRDIS imaging and SPHERE/IFS spectroscopic observations of PDS 70 b. The astrometric baseline now covers 6 yr, which allowed us to perform an orbital analysis. For the first time, we present spectrophotometry of the young planet which covers almost the entire near-infrared range (0.96–3.8 μm). We use different atmospheric models covering a large parameter space in temperature, log g, chemical composition, and cloud properties to characterize the properties of the atmosphere of PDS 70 b. Results. PDS 70 b is most likely orbiting the star on a circular and disk coplanar orbit at ~22 au inside the gap of the disk. We find a range of models that can describe the spectrophotometric data reasonably well in the temperature range 1000–1600 K and log g no larger than 3.5 dex. The planet radius covers a relatively large range between 1.4 and 3.7 RJ with the larger radii being higher than expected from planet evolution models for the age of the planet of 5.4 Myr. Conclusions. This study provides a comprehensive data set on the orbital motion of PDS 70 b, indicating a circular orbit and a motion coplanar with the disk. The first detailed spectral energy distribution of PDS 70 b indicates a temperature typical of young giant planets. The detailed atmospheric analysis indicates that a circumplanetary disk may contribute to the total planetflux.

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