scholarly journals Recent Work on Bipolar Nebulae

1983 ◽  
Vol 103 ◽  
pp. 45-55
Author(s):  
Martin Cohen
Keyword(s):  
Main Sequence ◽  
Near Infrared ◽  
Far Infrared ◽  
Carbon Star ◽  
Infrared Photometry ◽  
Bipolar Structure ◽  
Rapid Transition ◽  
Red Giant ◽  
Dusty Disks ◽  
Heterogeneous Class

Recent results obtained from studies of bipolar nebulae with a variety of techniques are described. Nebular polarization maps and spectropolarimetry, near-infrared spectroscopy, far-infrared photometry, radio maser and continuum work all have contributed to our knowledge of this heterogeneous class of objects. Some are certainly pre-main-sequence; others are likely to represent the rapid transition from red giant to planetary nebula. At least one dust-shrouded carbon star (CIT 6) and one visual binary with an O-star primary (MWC 349) have bipolar structure. Equatorial dusty disks must be common occurrences at different phases of stellar evolution.

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 On the Nature of the Binary Components of RX J0806.3+1527

2004 ◽  
Vol 194 ◽  
pp. 122-123
Author(s):  
K. Reinsch ◽  
V. Burwitz ◽  
R. Schwarz
Keyword(s):  
Main Sequence ◽  
Near Infrared ◽  
Flux Distribution ◽  
Galactic Disk ◽  
Modulation Amplitude ◽  
Direct Impact ◽  
Infrared Photometry ◽  
Short Period ◽  
Cyclotron Emission ◽  
Magnetic Nature

AbstractWe present imaging circular polarimetry and near-infrared photometry of the suspected ultra-short period while-dwarf binary RX J0806.3+1527 obtained with the ESO VLT and discuss the implications for a possible magnetic nature of the white dwarf accretor and the constraints derived for the nature of the donor star. Our V-filter data, show marginally significant circular polarization with a modulation amplitude of ≈ 0.5% typical for cyclotron emission from an accretion column in a magnetic field of order 10MG and not compatible with a direct-impact accretor model. The optical to near-infrared flux distribution is well described by a single blackbody with temperature kTbb = 35000 K and excludes a main-sequence stellar donor unless the binary is located several scale heights above the galactic disk population.

scholarly journals VISION – Vienna survey in Orion

2019 ◽  
Vol 622 ◽  
pp. A149 ◽  
Author(s):  
Josefa Elisabeth Großschedl ◽  
João Alves ◽  
Paula S. Teixeira ◽  
Hervé Bouy ◽  
Jan Forbrich ◽  
...  
Keyword(s):  
Main Sequence ◽  
Near Infrared ◽  
Far Infrared ◽  
Circumstellar Disks ◽  
Mass Star ◽  
Main Sequence Stars ◽  
Star Forming ◽  
Spatial Coverage ◽  
Significant Difference ◽  
Infrared Data

We have extended and refined the existing young stellar object (YSO) catalogs for the Orion A molecular cloud, the closest massive star-forming region to Earth. This updated catalog is driven by the large spatial coverage (18.3 deg2, ∼950 pc2), seeing limited resolution (∼0.7″), and sensitivity (Ks < 19 mag) of the ESO-VISTA near-infrared survey of the Orion A cloud (VISION). Combined with archival mid- to far-infrared data, the VISTA data allow for a refined and more robust source selection. We estimate that among previously known protostars and pre-main-sequence stars with disks, source contamination levels (false positives) are at least ∼6.4% and ∼2.3%, respectively, mostly due to background galaxies and nebulosities. We identify 274 new YSO candidates using VISTA/Spitzer based selections within previously analyzed regions, and VISTA/WISE based selections to add sources in the surroundings, beyond previously analyzed regions. The WISE selection method recovers about 59% of the known YSOs in Orion A’s low-mass star-forming part L1641, which shows what can be achieved by the all-sky WISE survey in combination with deep near-infrared data in regions without the influence of massive stars. The new catalog contains 2980 YSOs, which were classified based on the de-reddened mid-infrared spectral index into 188 protostars, 185 flat-spectrum sources, and 2607 pre-main-sequence stars with circumstellar disks. We find a statistically significant difference in the spatial distribution of the three evolutionary classes with respect to regions of high dust column-density, confirming that flat-spectrum sources are at a younger evolutionary phase compared to Class IIs, and are not a sub-sample seen at particular viewing angles.

scholarly journals Starbursts in and out of the star-formation main sequence

2018 ◽  
Vol 616 ◽  
pp. A110 ◽  
Author(s):  
D. Elbaz ◽  
R. Leiton ◽  
N. Nagar ◽  
K. Okumura ◽  
M. Franco ◽  
...  
Keyword(s):  
Star Formation ◽  
Main Sequence ◽  
Near Infrared ◽  
Compact Star ◽  
Far Infrared ◽  
High Mass ◽  
Star Forming ◽  
Stellar Component ◽  
Public Data ◽  
Gas Fractions

Aims. We use high-resolution continuum images obtained with the Atacama Large Millimeter Array (ALMA) to probe the surface density of star formation in z ~ 2 galaxies and study the different physical properties between galaxies within and above the star-formation main sequence of galaxies. Methods. We use ALMA images at 870 μm with 0.2 arcsec resolution in order to resolve star formation in a sample of eight star-forming galaxies at z ~ 2 selected among the most massive Herschel galaxies in the GOODS-South field. This sample is supplemented with eleven galaxies from the public data of the 1.3 mm survey of the Hubble Ultra-Deep Field, HUDF. We derive dust and gas masses for the galaxies, compute their depletion times and gas fractions, and study the relative distributions of rest-frame ultraviolet (UV) and far-infrared (FIR) light. Results. ALMA reveals systematically dense concentrations of dusty star formation close to the center of the stellar component of the galaxies. We identify two different starburst regimes: (i) the classical population of starbursts located above the SFR-M⋆ main sequence, with enhanced gas fractions and short depletion times and (ii) a sub-population of galaxies located within the scatter of the main sequence that experience compact star formation with depletion timescales typical of starbursts of ~150 Myr. In both starburst populations, the FIR and UV are distributed in distinct regions and dust-corrected star formation rates (SFRs) estimated using UV-optical-near-infrared data alone underestimate the total SFR. Starbursts hidden in the main sequence show instead the lowest gas fractions of our sample and could represent the last stage of star formation prior to passivization. Being Herschel-selected, these main sequence galaxies are located in the high-mass end of the main sequence, hence we do not know whether these “starbursts hidden in the main sequence” also exist below 1011 M⊙. Active galactic nuclei (AGNs) are found to be ubiquitous in these compact starbursts, suggesting that the triggering mechanism also feeds the central black hole or that the active nucleus triggers star formation.

Far-infrared photometry of low-mass pre-main-sequence stars with broad CO wings

1986 ◽  
Vol 301 ◽  
pp. 894 ◽  
Author(s):  
N. J., II Evans ◽  
R. M. Levreault ◽  
P. M. Harvey
Keyword(s):  
Main Sequence ◽  
Far Infrared ◽  
Infrared Photometry ◽  
Main Sequence Stars ◽  
Low Mass

scholarly journals A Comparative Anatomy of Dusty Disks Imaged by NICMOS

2004 ◽  
Vol 202 ◽  
pp. 308-315
Author(s):  
Glenn Schneider ◽  
Dean C. Hines ◽  
Murray Silverstone ◽  
Alycia J. Weinberger ◽  
Keyword(s):  
Main Sequence ◽  
Near Infrared ◽  
Hubble Space Telescope ◽  
Comparative Anatomy ◽  
Scattered Light ◽  
Infrared Camera ◽  
Main Sequence Stars ◽  
Spatially Resolved ◽  
T Tauri ◽  
Dusty Disks

Using the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) on the Hubble Space Telescope we have conducted a coronagraphic imaging survey of 18 main sequence stars with large infrared excesses, searching for circumstellar dust (debris) in scattered light. Dusty disks with radial and hemispheric brightness anisotropies and complex morphologies, both possibly indicative of dynamical interactions with unseen planetary mass companions, were spatially resolved and imaged around three young (≲ 10Myr old) stars. From these observations we describe the debris systems around: a) HR 4796A (A0V), a 70 AU radius ring less than 14 AU wide with unequal ansal flux densities; b) HD 141569A (Herbig Ae/Be), a 400 AU radius disk with a 40 AU wide gap; and c) TW Hya (K7 T-Tauri), a pole-on circularly symmetric disk with a radial break in its surface density of scattering particles. Additionally, our non-detection of scattered light and high precision photometry of a fourth system of similar age, HD 98800 A/B, coupled with mid and thermal IR measurements, greatly constrain a likely model for the debris about the B component.

scholarly journals Infrared observations of GGD objects

1987 ◽  
Vol 122 ◽  
pp. 125-126
Author(s):  
R. Carballo ◽  
C. Eiroa ◽  
A. Mampaso
Keyword(s):  
Main Sequence ◽  
Near Infrared ◽  
Far Infrared ◽  
Infrared Emission ◽  
Be Stars ◽  
Main Sequence Stars ◽  
Infrared Excess ◽  
Dark Clouds ◽  
Infrared Sources ◽  
Different Characteristics

We present accurate positions and near infrared photometry (Table I) of 11 point-like objects in the neighbourhood of GGD objects obtained on the 1.55 m and on the 1.23 m in Teide Obs. and Calar Alto Obs. respectively, in Spain. Several of the near infrared sources are directly associated with the GGD nebulae and/or are candidate for their excitation. In addition some of them seem to be the near infrared counterparts of IRAS sources. We believe, on the basis of their infrared excess, far infrared emission (IRAS), association with nebulosity, coincidence with H2O masers or the fact that in most cases the observed luminosities are higher than those expected for main sequence stars, that most of them (9/12) are young stars embedded in the dark clouds which contain the GGD objects. The loci of the detected sources in an (H-K,K-L) infrared two-colour diagram is the same as that obtained for known pre-main sequence stars, such as T Tauris and Herbig Ae-Be stars, indicating the presence of dust shells with temperatures in the range 800–1500 K. The observed range in luminosity, 10–4600 L⊙, added to other different characteristics found between them, such' as the presence, or absence, of H2O masers, indicates the interest for a detailed study of the infrared sources and related GGD nebulae.

Panchromatic Analysis for Nature of HIgh-z galaxies Tool (PANHIT)

2019 ◽  
Vol 15 (S341) ◽  
pp. 285-286
Author(s):  
Ken Mawatari ◽  
Akio K. Inoue ◽  
Satoshi Yamanaka ◽  
Takuya Hashimoto ◽  
Yoichi Tamura
Keyword(s):  
Physical Properties ◽  
Rest Frame ◽  
Near Infrared ◽  
Broad Band ◽  
Dust Emission ◽  
Far Infrared ◽  
Infrared Photometry ◽  
Spectral Emission ◽  
Line Flux ◽  
Faint Object

AbstractWe have developed a new SED fitting tool specialized for frontier redshift galaxies. It is a common case for high-z galaxies that the available data are restricted to rich optical to near-infrared photometry and few far-infrared (FIR) data deep enough to detect the faint object (e.g., HST/WFC3 + Spitzer/IRAC + ALMA). In such situation, one cannot perform a complicated modeling of dust emission in FIR regime. We then adopt simple treatment for the dust emission using empirical LIRG templates. Instead, we adopt a sophisticated and physically motivated modeling for stellar and nebular emission parts in rest-frame UV-to-optical regime. Our new code fits not only broad band photometry but also spectral emission line flux. There is an option to fit observed SED with two templates with different physical properties. Our new code, PANHIT, is now in public, and was already applied to some high-z frontier galaxies.

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