scholarly journals Young Stars in the Camelopardalis Dust and Molecular Clouds. VI. YSOs Verified by Spitzer and Akari Infrared Photometry

2010 ◽  
Vol 19 (1-2) ◽  
pp. 1-33
Author(s):  
V. Straižys ◽  
A. Kazlauskas
Keyword(s):  
Spectral Energy Distribution ◽  
Spectral Energy ◽  
H Ii Regions ◽  
Infrared Photometry ◽  
Class Iii ◽  
Star Forming ◽  
Star Forming Regions ◽  
Dusty Galaxies ◽  
Infrared Surveys ◽  
Infrared Sources

AbstractUsing photometric data of infrared surveys, young stellar object (YSO) status is verified for 141 objects selected in our previous papers in the Cassiopeia and Camelopardalis segment of the Milky Way bounded by Galactic coordinates (l, b) = (132-158°, ±12°). The area includes the known star- forming regions in the emission nebulae W3, W4 and W5 and the massive YSO AFGL490. Spectral energy distribution (SED) curves between 700 nm and 160 μm, constructed from the GSC 2, 2MASS, IRAS, MSX, Spitzer and AKARI data, are used to estimate the evolutionary stages of these stars. We confirm the YSO status for most of the objects. If all of the investigated objects were YSOs, 45% of them should belong to Class I, 41% to class II and 14% to Class III. However, SEDs of some of these objects can be affected by nearby extended infrared sources, like compact H II regions, infrared clusters or dusty galaxies.

scholarly journals An obscured AGN population hidden in the VIPERS galaxies: identification through spectral energy distribution decomposition

2020 ◽  
Vol 495 (2) ◽  
pp. 1853-1873
Author(s):  
E Pouliasis ◽  
G Mountrichas ◽  
I Georgantopoulos ◽  
A Ruiz ◽  
M Yang ◽  
...  
Keyword(s):  
Energy Distribution ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
Galactic Nuclei ◽  
Spectral Energy ◽  
X Ray ◽  
Star Forming ◽  
Star Forming Regions ◽  
Redshift Survey ◽  
Selection Of

ABSTRACT The detection of X-ray emission constitutes a reliable and efficient tool for the selection of active galactic nuclei (AGNs), although it may be biased against the most heavily absorbed AGNs. Simple mid-infrared (IR) broad-band selection criteria identify a large number of luminous and absorbed AGNs, yet again host contamination could lead to non-uniform and incomplete samples. Spectral energy distribution (SED) decomposition is able to decouple the emission from the AGN versus that from star-forming regions, revealing weaker AGN components. We aim to identify the obscured AGN population in the VIMOS Public Extragalactic Redshift Survey in the Canada–France–Hawaii Telescope Legacy Survey W1 field through SED modelling. We construct SEDs for 6860 sources and identify 160 AGNs at a high confidence level using a Bayesian approach. Using optical spectroscopy, we confirm the nature of ∼85 per cent of the AGNs. Our AGN sample is highly complete (∼92 per cent) compared to mid-IR colour-selected AGNs, including a significant number of galaxy-dominated systems with lower luminosities. In addition to the lack of X-ray emission (80 per cent), the SED fitting results suggest that the majority of the sources are obscured. We use a number of diagnostic criteria in the optical, IR, and X-ray regimes to verify these results. Interestingly, only 35 per cent of the most luminous mid-IR-selected AGNs have X-ray counterparts suggesting strong absorption. Our work emphasizes the importance of using SED decomposition techniques to select a population of type II AGNs, which may remain undetected by either X-ray or IR colour surveys.

scholarly journals Multiwavelength study of the G345.5+1.5 region

2019 ◽  
Vol 623 ◽  
pp. A141
Author(s):  
M. Figueira ◽  
C. López-Calderón ◽  
L. Bronfman ◽  
A. Zavagno ◽  
C. Hervías-Caimapo ◽  
...  
Keyword(s):  
Star Formation ◽  
Formation Process ◽  
Galactic Plane ◽  
Spectral Energy Distribution ◽  
Formation Rate ◽  
Spectral Energy ◽  
Transition Line ◽  
Star Forming ◽  
Star Forming Regions ◽  
Neutral Material

Context. The star formation process requires the dust and gas present in the Milky Way to self-assemble into dense reservoirs of neutral material where the new generation of stars will emerge. Star-forming regions are usually studied in the context of Galactic surveys, but dedicated observations are sometimes needed when the study reaches beyond the survey area. Aims. A better understanding of the star formation process in the Galaxy can be obtained by studying several regions. This allows increasing the sample of objects (clumps, cores, and stars) for further statistical works and deeper follow-up studies. Here, we studied the G345.5+1.5 region, which is located slightly above the Galactic plane, to understand its star formation properties. Methods. We combined Large Apex BOlometer CAmera (LABOCA) and 12CO(4−3) transition line (NANTEN2) observations complemented with the Hi-GAL and Spitzer-GLIMPSE surveys to study the star formation toward this region. We used the Clumpfind algorithm to extract the clumps from the 870 μm and 12CO(4−3) data. Radio emission at 36 cm was used to estimate the number of H II regions and to remove the contamination from the free–free emission at 870 μm. We employed color–color diagrams and spectral energy distribution (SED) slopes to distinguish between prestellar and protostellar clumps. We studied the boundedness of the clumps through the virial parameter. Finally, we estimated the star formation efficiency (SFE) and star formation rate (SFR) of the region and used the Schmidt–Kennicutt diagram to compare its ability to form stars with other regions of the Galactic plane. Results. Of the 13 radio sources that we found using the MGPS-2 catalog, 7 are found to be associated with H II regions corresponding to late-B or early-O stars. We found 45 870 μm clumps with diameters between 0.4 and 1.2 pc and masses between 43 M⊙ and 3923 M⊙, and 107 12CO clumps with diameters between 0.4 and 1.3 pc and masses between 28 M⊙ and 9433 M⊙. More than 50% of the clumps are protostellar and bounded and are able to host (massive) star formation. High SFR and SFR density (ΣSFR) values are associated with the region, with an SFE of a few percent. Conclusions. With submillimeter, CO transition, and short-wavelength infrared observations, our study reveals a population of massive stars, protostellar and bound starless clumps, toward G345.5+1.5. This region is therefore actively forming stars, and its location in the starburst quadrant of the Schmidt–Kennicutt diagram is comparable to other star-forming regions found within the Galactic plane.

scholarly journals Subaru/HSC deep optical imaging of infrared sources in the AKARI North Ecliptic Pole-Wide field

2020 ◽  
Vol 500 (4) ◽  
pp. 5024-5042
Author(s):  
Nagisa Oi ◽  
Tomotsugu Goto ◽  
Hideo Matsuhara ◽  
Yousuke Utsumi ◽  
Rieko Momose ◽  
...  
Keyword(s):  
Optical Imaging ◽  
Thermal Emission ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
Spectral Energy ◽  
Wide Field ◽  
Star Forming ◽  
The North ◽  
Almost All ◽  
Infrared Sources

ABSTRACT We present a five-broad-band (grizy) photometric catalogue of Subaru/Hyper Suprime-Cam (HSC) optical imaging observations at around the North Ecliptic Pole (NEP) where the AKARI infrared (IR) satellite conducted a large survey (NEP-Wide survey). The observations cover almost all the NEP-Wide survey field down to the depth of 28.1, 26.8, 26.3, 25.5, and 25.0 mag (5σ) at grizy, respectively. The five-band HSC catalogue contains about 2.6 million objects, and 70 959 AKARI NEP-Wide counterpart sources are identified in the catalogue. We added existing supplementary catalogues from the u band to the far-IR band, and estimated photo-z for the AKARI-HSC sources. We achieved σΔz/(1 + zs) = 0.06 and an outlier rate of 13.4 per cent at z = 0.2–1.5. Using the spectral energy distribution (SED) template fitting, we classified the AKARI-HSC galaxies into four categories, namely quiescent, star-forming, Type1 active galactic nucleus (AGN), and Type2 AGN, in each redshift bin. At z > 1, the mean SED of star-forming galaxies in mid-IR (3–10 μm) range is significantly different from that of spiral galaxies in the nearby Universe, indicating that many of star-forming galaxies at z > 1 contain a heat source capable of heating dust to temperatures that radiate thermal emission in the mid-IR range. Furthermore, we estimated the number fraction of AGNs (fAGN) in each bin of redshift and IR luminosity (LIR), and examined the dependence of redshift and LIR. In log(LIR/L⊙) = 11.0–14.0, the fAGN shows a significant increase with increasing redshift, regardless of the LIR bins. In contrast, the fAGN shows a slight increase against LIR at z < 1 and no increase with increasing LIR at z > 1.

scholarly journals ALMA band 8 observations of DLA 2233+131 at z = 3.150

2020 ◽  
Vol 72 (2) ◽  
Author(s):  
Kazuyuki Ogura ◽  
Hideki Umehata ◽  
Yoshiaki Taniguchi ◽  
Yuichi Matsuda ◽  
Nobunari Kashikawa ◽  
...  
Keyword(s):  
Emission Line ◽  
Hubble Space Telescope ◽  
High Redshift ◽  
Spectral Energy Distribution ◽  
Spectral Energy ◽  
High Redshift Galaxies ◽  
Star Forming ◽  
Optical Images ◽  
Dusty Galaxies ◽  
Good Laboratory

Abstract We present our ALMA Band 8 observations of a damped Ly$\alpha$ absorption (DLA) system at $z = 3.150$ observed in the spectrum of the quasar Q2233+131 at $z = 3.295$. The optical counterpart of this DLA has been identified and it shows a double-peaked Ly$\alpha$ emission line. Since one possible origin of DLAs at high redshift is an outflowing gas from star-forming galaxies, DLA 2233+131 provides a good laboratory to investigate the nature of high-z DLAs. Motivated by this, we have carried out ALMA band 8 observations to study the [C ii] line in this system. However, we do not detect any significant emission line in the observed pass bands. Instead, we have serendipitously found three submm continuum sources in the observed sky area. One appears to be the quasar Q2233+131 itself while the other two sources are newly identified submm galaxies (SMGs), called SMG1 and SMG2 in this paper. They are located at a separation of ${4{^{\prime \prime }_{.}}7}$ and ${8{^{\prime \prime }_{.}}1}$ from Q2233+131, respectively. Their 646 μm fluxes are $6.35\:$mJy and $6.43\:$mJy, respectively, being higher than that of Q2233+131, $3.62\:$mJy. Since these two SMGs are not detected in the optical images obtained with the Hubble Space Telescope and the Subaru Telescope, they have a very red spectral energy distribution. It is, therefore, suggested that they are high-redshift galaxies or very dusty galaxies at intermediate redshift, although we cannot rule out the possibility that they are optically very faint SMG analogs at low redshift. Follow-up observations will be necessary to explore the nature of this interesting region.

scholarly journals Radiative properties of the first galaxies: rapid transition between UV and infrared bright phases

2019 ◽  
Vol 488 (2) ◽  
pp. 2629-2643 ◽  
Author(s):  
Shohei Arata ◽  
Hidenobu Yajima ◽  
Kentaro Nagamine ◽  
Yuexing Li ◽  
Sadegh Khochfar
Keyword(s):  
Initial Conditions ◽  
Spectral Energy Distribution ◽  
Radiative Properties ◽  
Spectral Energy ◽  
Star Forming ◽  
Star Forming Regions ◽  
Halo Masses ◽  
First Galaxies ◽  
Uv Photons ◽  
Supernova Feedback

ABSTRACT Recent observations have successfully detected UV-bright and infrared-bright galaxies in the epoch of reionization. However, the origin of their radiative properties has not been understood yet. Combining cosmological hydrodynamic simulations and radiative transfer calculations, we present predictions of multiwavelength radiative properties of the first galaxies at z ∼ 6–15. Using zoom-in initial conditions, we investigate three massive galaxies and their satellites in different environment and halo masses at z = 6: $M_{\rm h}= 2.4\times 10^{10}\,$, $1.6\times 10^{11}\, $, and $0.7\times 10^{12}\, {\rm M_{\odot }}$. We find that most of the gas and dust are ejected from star-forming regions by supernova feedback, which allows the UV photons to escape. We show that the peak of the spectral energy distribution (SED) rapidly changes between UV and infrared wavelengths on a time-scale of ∼ 100 Myr due to intermittent star formation and feedback, and the escape fraction of UV photons fluctuates in the range of 0.2–0.8 at z < 10 with a time-averaged value of 0.3. When dusty gas covers the star-forming regions, the galaxies become bright in the observed-frame sub-millimeter wavelengths. We predict the detectability of high-z galaxies with the Atacama Large Millimeter Array (ALMA). For a sensitivity limit of $0.1\, {\rm mJy}$ at $850\, {\rm \mu m}$, the detection probability of galaxies in haloes $M_{\rm h}\gtrsim 10^{11}\, \, {\rm M_{\odot }}$ at z ≲ 7 exceeds fifty per cent. We argue that supernova feedback can produce the observed diversity of SEDs for high-z galaxies.

scholarly journals An infrared study of the high-mass, multistage star-forming region IRAS 12272−6240

2020 ◽  
Vol 496 (3) ◽  
pp. 3358-3370
Author(s):  
Mauricio Tapia ◽  
Paolo Persi ◽  
Miguel Roth ◽  
Davide Elia
Keyword(s):  
Near Infrared ◽  
Narrow Band ◽  
Spectral Energy Distribution ◽  
Central Star ◽  
Young Stellar Objects ◽  
High Mass ◽  
Spectral Energy ◽  
H Ii Regions ◽  
Infrared Study ◽  
Star Forming

ABSTRACT IRAS 12272−6240 is a complex star-forming region with a compact massive dense clump (DC) and several associated masers, located at a well-determined distance of d = 9.3 kpc from the Sun. For this study, we obtained sub-arcsec broad- and narrow-band near-infrared (near-IR) imaging and low-resolution spectroscopy with the Baade/Magellan telescope and its camera PANIC. Mosaics of size 2 × 2 arcmin2 in the JHKs bands and with narrow-band filters centred in the 2.12 μm H2 and 2.17 μm Br γ lines were analysed in combination with Hi-GAL/Herschel and archive IRAC/Spitzer and WISE observations. We found that the compact DC houses two Class I young stellar objects (YSOs) that probably form a 21000 -au-wide binary system. Its combined 1–1200 μm spectral energy distribution is consistent with an O9V central star with a $10^{-2} \, \mathrm{M}_\odot$ disc and a $1.3 \times 10^4 \, \mathrm{M}_\odot$ dust envelope. Its total luminosity is $8.5 \times 10^4 \, \mathrm{L}_\odot$. A series of shocked H2 emission knots are found in its close vicinity, confirming the presence of outflows. IRAS 12272−6240 is at the centre of an embedded cluster with a mean age of 1 Myr and 2.6 pc in size that contains more than 150 stars. At its nucleus, we found a more compact and considerably younger subcluster containing the YSOs. We also identified and classified the O-type central stars of two dusty radio/IR H ii regions flanking the protostars. Our results confirm that these elements form a single giant young complex where massive star formation processes started some 1 Myr ago and are still active.

scholarly journals Hardness of ionizing radiation fields in MaNGA star-forming galaxies

2021 ◽  
Author(s):  
Nimisha Kumari ◽  
Ricardo Amorín ◽  
Enrique Pérez-Montero ◽  
Jose Vílchez ◽  
Roberto Maiolino
Keyword(s):  
Ionizing Radiation ◽  
Spectral Energy Distribution ◽  
Radiation Hardness ◽  
Spectral Energy ◽  
H Ii Regions ◽  
Low Mass Stars ◽  
Data Set ◽  
Star Forming ◽  
Radiation Fields ◽  
Hard Radiation

Abstract We investigate radiation hardness within a representative sample of 67 nearby (0.02 ≲  z  ≲ 0.06) star-forming (SF) galaxies using the integral field spectroscopic data from the MaNGA survey. The softness parameter η = $\frac{O^{+}/O^{2+}}{S^{+}/S^{2+}}$ is sensitive to the spectral energy distribution of the ionizing radiation. We study η via the observable quantity η′ ($=\frac{[O\rm \small {II}]/[O\rm \small {III}]}{[S\rm \small {II}][S\rm \small {III}]}$) We analyse the relation between radiation hardness (traced by η and η′) and diagnostics sensitive to gas-phase metallicity, electron temperature, density, ionization parameter, effective temperature and age of ionizing populations. It is evident that low metallicity is accompanied by low log η′, i.e. hard radiation field. No direct relation is found between radiation hardness and other nebular parameters though such relations can not be ruled out. We provide empirical relations between log $\rm \eta$ and strong emission line ratios N2, O3N2 and Ar3O3 which will allow future studies of radiation hardness in SF galaxies where weak auroral lines are undetected. We compare the variation of [O iii]/[O ii] and [S iii]/[S ii] for MaNGA data with SF galaxies and H ii regions within spiral galaxies from literature, and find that the similarity and differences between different data set is mainly due to the metallicity. We find that predictions from photoionizaion models considering young and evolved stellar populations as ionizing sources in good agreement with the MaNGA data. This comparison also suggests that hard radiation fields from hot and old low-mass stars within or around SF regions might significantly contribute to the observed η values.

scholarly journals Age Spreads and Systematics in λ Orionis with Gaia DR2 and the SPOTS Tracks

2022 ◽  
Vol 924 (2) ◽  
pp. 84
Author(s):  
Lyra Cao ◽  
Marc H. Pinsonneault ◽  
Lynne A. Hillenbrand ◽  
Michael A. Kuhn
Keyword(s):  
Main Sequence ◽  
Spectral Energy Distribution ◽  
Open Clusters ◽  
Spectral Energy ◽  
Class Iii ◽  
Distribution Fitting ◽  
Star Forming ◽  
Derived Properties ◽  
Minimum Age ◽  
Stellar Models

Abstract In this paper we investigate the robustness of age measurements, age spreads, and stellar models in young pre-main-sequence stars. For this effort, we study a young cluster, λ Orionis, within the Orion star-forming complex. We use Gaia data to derive a sample of 357 targets with spectroscopic temperatures from spectral types or from the automated spectroscopic pipeline in APOGEE Net. After accounting for systematic offsets between the spectral type and APOGEE temperature systems, the derived properties of stars on both systems are consistent. The complex interstellar medium, with variable local extinction, motivates a star-by-star dereddening approach. We use a spectral energy distribution fitting method calibrated on open clusters for the Class III stars. For the Class II population, we use a Gaia G-RP dereddening method, minimizing systematics from disks, accretion, and other physics associated with youth. The cluster age is systematically different in models incorporating the structural impact of starspots or magnetic fields than in nonmagnetic models. Our mean ages range from 2–3 Myr (nonmagnetic models) to 3.9 ± 0.2 Myr in the SPOTS model (f = 0.34). We find that star-by-star dereddening methods distinguishing between pre-main-sequence classes provide a smaller age spread than techniques using a uniform extinction, and we infer a minimum age spread of 0.19 dex and a typical age spread of 0.35 dex after modeling age distributions convolved with observed errors. This suggests that the λ Ori cluster may have a long star formation timescale and that spotted stellar models significantly change age estimates for young clusters.

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