scholarly journals Surveying the Giant H ii Regions of the Milky Way with SOFIA. III. W49A

2021 ◽  
Vol 923 (2) ◽  
pp. 198
Author(s):  
James M. De Buizer ◽  
Wanggi Lim ◽  
Mengyao Liu ◽  
Nicole Karnath ◽  
James T. Radomski
Keyword(s):  
Near Infrared ◽  
Milky Way ◽  
Infrared Imaging ◽  
Physical Nature ◽  
Infrared Emission ◽  
Spectral Energy ◽  
H Ii Regions ◽  
Extended Radio ◽  
The Galaxy ◽  
Western Side

Abstract We present our third set of results from our mid-infrared imaging survey of Milky Way Giant H ii regions with our detailed analysis of W49A, one of the most distant, yet most luminous, GH ii regions in the Galaxy. We used the FORCAST instrument on the Stratospheric Observatory For Infrared Astronomy (SOFIA) to obtain 20 and 37 μm images of the entire ∼5.′0 × 3.′5 infrared-emitting area of W49A at a spatial resolution of ∼3″. Utilizing these SOFIA data in conjunction with previous multiwavelength observations from the near-infrared to radio, including Spitzer-IRAC and Herschel-PACS archival data, we investigate the physical nature of individual infrared sources and subcomponents within W49A. For individual compact sources, we used the multiwavelength photometry data to construct spectral energy distributions (SEDs) and fit them with massive young stellar object (MYSO) SED models and find 22 sources that are likely to be MYSOs. Ten new sources are identified for the first time in this work. Even at 37 μm we are unable to detect infrared emission from the sources on the western side of the extremely extinguished ring of compact radio emission sources known as the Welch Ring. Utilizing multiwavelength data, we derived luminosity-to-mass ratio and virial parameters of the extended radio subregions of W49A to estimate their relative ages and find that overall the subcomponents of W49A have a very small spread in evolutionary state compared to our previously studied GH ii regions.

scholarly journals Planck’s dusty GEMS

2018 ◽  
Vol 620 ◽  
pp. A60 ◽  
Author(s):  
R. Cañameras ◽  
N. P. H. Nesvadba ◽  
M. Limousin ◽  
H. Dole ◽  
R. Kneissl ◽  
...  
Keyword(s):  
Star Formation ◽  
Near Infrared ◽  
Infrared Imaging ◽  
High Redshift ◽  
Dust Emission ◽  
Galaxy Cluster ◽  
Star Forming ◽  
The Galaxy ◽  
Mass Outflow ◽  
Gas Accretion

We report the discovery of a molecular wind signature from a massive intensely star-forming clump of a few 109 M⊙, in the strongly gravitationally lensed submillimeter galaxy “the Emerald” (PLCK_G165.7+49.0) at z = 2.236. The Emerald is amongst the brightest high-redshift galaxies on the submillimeter sky, and was initially discovered with the Planck satellite. The system contains two magnificient structures with projected lengths of 28.5″ and 21″ formed by multiple, near-infrared arcs, falling behind a massive galaxy cluster at z = 0.35, as well as an adjacent filament that has so far escaped discovery in other wavebands. We used HST/WFC3 and CFHT optical and near-infrared imaging together with IRAM and SMA interferometry of the CO(4–3) line and 850 μm dust emission to characterize the foreground lensing mass distribution, construct a lens model with LENSTOOL, and calculate gravitational magnification factors between 20 and 50 in most of the source. The majority of the star formation takes place within two massive star-forming clumps which are marginally gravitationally bound and embedded in a 9 × 1010 M⊙, fragmented disk with 20% gas fraction. The stellar continuum morphology is much smoother and also well resolved perpendicular to the magnification axis. One of the clumps shows a pronounced blue wing in the CO(4–3) line profile, which we interpret as a wind signature. The mass outflow rates are high enough for us to suspect that the clump might become unbound within a few tens of Myr, unless the outflowing gas can be replenished by gas accretion from the surrounding disk. The velocity offset of –200 km s−1 is above the escape velocity of the clump, but not that of the galaxy overall, suggesting that much of this material might ultimately rain back onto the galaxy and contribute to fueling subsequent star formation.

scholarly journals Diffraction Limited Near Infrared Imaging of the Central Parsec of the Galaxy

1994 ◽  
Vol 158 ◽  
pp. 379-381
Author(s):  
A. Eckart ◽  
R. Genzel ◽  
R. Hofmann ◽  
B.J. Sams ◽  
L.E. Tacconi-Garman
Keyword(s):  
Near Infrared ◽  
Infrared Imaging ◽  
Core Radius ◽  
The Galaxy ◽  
K 13 ◽  
Sgr A ◽  
Central Parsec ◽  
Stellar Sources ◽  
Stellar Density ◽  
Source Number

We present deep 1.6 and 2.2 μm images of the central parsec of the Galaxy at a resolution of 0.15″. Most of the flux in earlier seeing limited images comes from about 340 unresolved stellar sources with K≤14. The IRS 16 and 13 complexes are resolved into about two dozen and half a dozen sources, a number of which are probably luminous hot stars. We confirm the presence of a blue near infrared object (K≈13) at the position of the compact radio source Sgr A∗. The spatial centroid of the source number distribution is consistent with the position of Sgr A∗ but not with a position in the IRS 16 complex. The stellar surface density in the central 10″ is very well fitted by an isothermal cluster model with a well defined core radius. The derived core radius of all 340 sources is 0.15±0.05 pc. The central stellar density is a few times 107 M⊙ pc−3. Buildup of massive stars by merging of lower mass stars and collisional disruption of giant atmospheres are very probable processes in the central 0.2 pc.

scholarly journals The Nuclear Star Cluster of the Milky Way: Star Formation, Stellar Collisions and Central Dark Mass

1996 ◽  
Vol 174 ◽  
pp. 81-90
Author(s):  
R. Genzel
Keyword(s):  
Star Formation ◽  
Near Infrared ◽  
Milky Way ◽  
Infrared Imaging ◽  
Star Cluster ◽  
Structure Evolution ◽  
Late Type ◽  
Massive Black Hole ◽  
Imaging And Spectroscopy ◽  
Central Parsec

High resolution near-infrared imaging and spectroscopy now gives detailed information about the structure, evolution and mass distribution in the nuclear star cluster of the Milky Way. The central parsec is powered by a cluster of luminous and helium rich, blue supergiants/Wolf-Rayet stars. The most likely scenario for the formation of the massive stars is a star formation burst a few million years ago at which time a dense gas cloud may have fallen into the center. The stellar density in the ∼ 0.3 pc radius central core is high enough that collisions with main sequence stars destroy the largest late type giant stars. Radial velocity measurements for about 300 early and late type stars between 0.1 and 5pc radius from the dynamic center now strongly favor the existence of a central dark mass of 2.5 − 3.3 × 106M⊙ (density (109M⊙pc−3, M/L2μm) ∼ 100M⊙/L⊙) within 0.1pc of the dynamic center. This central dark mass cannot be a cluster of neutron stars. It is either a compact cluster of stellar black holes or, most likely, a single massive black hole.

scholarly journals Milky Way demographics with the VVV survey

2018 ◽  
Vol 619 ◽  
pp. A4 ◽  
Author(s):  
Javier Alonso-García ◽  
Roberto K. Saito ◽  
Maren Hempel ◽  
Dante Minniti ◽  
Joyce Pullen ◽  
...  
Keyword(s):  
Near Infrared ◽  
Milky Way ◽  
Stellar Populations ◽  
Wide Field ◽  
Public Survey ◽  
Wide Field Of View ◽  
Spread Function ◽  
The Galaxy ◽  
Infrared Wavelengths ◽  
Galactic Stellar Populations

Context. The inner regions of the Galaxy are severely affected by extinction, which limits our capability to study the stellar populations present there. The Vista Variables in the Vía Láctea (VVV) ESO Public Survey has observed this zone at near-infrared wavelengths where reddening is highly diminished. Aims. By exploiting the high resolution and wide field-of-view of the VVV images we aim to produce a deep, homogeneous, and highly complete database of sources that cover the innermost regions of our Galaxy. Methods. To better deal with the high crowding in the surveyed areas, we have used point spread function (PSF)-fitting techniques to obtain a new photometry of the VVV images, in the ZY JHKs near-infrared filters available. Results. Our final catalogs contain close to one billion sources, with precise photometry in up to five near-infrared filters, and they are already being used to provide an unprecedented view of the inner Galactic stellar populations. We make these catalogs publicly available to the community. Our catalogs allow us to build the VVV giga-CMD, a series of color-magnitude diagrams of the inner regions of the Milky Way presented as supplementary videos. We provide a qualitative analysis of some representative CMDs of the inner regions of the Galaxy, and briefly mention some of the studies we have developed with this new dataset so far.

scholarly journals Stellar substructures in the periphery of the magellanic clouds with the VISTA hemisphere survey from the red clump and other tracers

2021 ◽  
Author(s):  
Dalal El Youssoufi ◽  
Maria-Rosa L Cioni ◽  
Cameron P M Bell ◽  
Richard de Grijs ◽  
Martin A T Groenewegen ◽  
...  
Keyword(s):  
Near Infrared ◽  
Infrared Imaging ◽  
Magellanic Clouds ◽  
Imaging Data ◽  
The North ◽  
The Galaxy ◽  
History Of ◽  
Northern Side ◽  
Red Clump ◽  
Interaction History

Abstract We study the morphology of the stellar periphery of the Magellanic Clouds in search of substructure using near–infrared imaging data from the VISTA Hemisphere Survey (VHS). Based on the selection of different stellar populations using the (J − Ks, Ks) colour–magnitude diagram, we confirm the presence of substructures related to the interaction history of the Clouds and find new substructures on the eastern side of the LMC disc which may be owing to the influence of the Milky Way, and on the northern side of the SMC, which is probably associated to the ellipsoidal structure of the galaxy. We also study the luminosity function of red clump stars in the SMC and confirm the presence of a bi–modal distance distribution, in the form of a foreground population. We find that this bi–modality is still detectable in the eastern regions of the galaxy out to a 10○ distance from its centre. Additionally, a background structure is detected in the North between 7○ and 10○ from the centre which might belong to the Counter Bridge, and a foreground structure is detected in the South between 6○ and 8○ from the centre which might be linked to the Old Bridge.

scholarly journals Simulating JWST deep extragalactic imaging surveys and physical parameter recovery

2020 ◽  
Vol 640 ◽  
pp. A67
Author(s):  
O. B. Kauffmann ◽  
O. Le Fèvre ◽  
O. Ilbert ◽  
J. Chevallard ◽  
C. C. Williams ◽  
...  
Keyword(s):  
Star Formation ◽  
Near Infrared ◽  
High Redshift ◽  
Spectral Energy Distribution ◽  
Formation Rate ◽  
Spectral Energy ◽  
Photometric Redshifts ◽  
The Galaxy ◽  
Stellar Masses ◽  
The Impact

We present a new prospective analysis of deep multi-band imaging with the James Webb Space Telescope (JWST). In this work, we investigate the recovery of high-redshift 5 <  z <  12 galaxies through extensive image simulations of accepted JWST programs, including the Early Release Science in the EGS field and the Guaranteed Time Observations in the HUDF. We introduced complete samples of ∼300 000 galaxies with stellar masses of log(M*/M⊙) > 6 and redshifts of 0 <  z <  15, as well as galactic stars, into realistic mock NIRCam, MIRI, and HST images to properly describe the impact of source blending. We extracted the photometry of the detected sources, as in real images, and estimated the physical properties of galaxies through spectral energy distribution fitting. We find that the photometric redshifts are primarily limited by the availability of blue-band and near-infrared medium-band imaging. The stellar masses and star formation rates are recovered within 0.25 and 0.3 dex, respectively, for galaxies with accurate photometric redshifts. Brown dwarfs contaminating the z >  5 galaxy samples can be reduced to < 0.01 arcmin−2 with a limited impact on galaxy completeness. We investigate multiple high-redshift galaxy selection techniques and find that the best compromise between completeness and purity at 5 <  z <  10 using the full redshift posterior probability distributions. In the EGS field, the galaxy completeness remains higher than 50% at magnitudes mUV <  27.5 and at all redshifts, and the purity is maintained above 80 and 60% at z ≤ 7 and 10, respectively. The faint-end slope of the galaxy UV luminosity function is recovered with a precision of 0.1–0.25, and the cosmic star formation rate density within 0.1 dex. We argue in favor of additional observing programs covering larger areas to better constrain the bright end.

scholarly journals GOODS-ALMA: Optically dark ALMA galaxies shed light on a cluster in formation at z = 3.5

2020 ◽  
Vol 642 ◽  
pp. A155 ◽  
Author(s):  
L. Zhou ◽  
D. Elbaz ◽  
M. Franco ◽  
B. Magnelli ◽  
C. Schreiber ◽  
...  
Keyword(s):  
Near Infrared ◽  
Far Infrared ◽  
Spectral Energy ◽  
Photometric Redshifts ◽  
Cluster Galaxy ◽  
Massive Galaxies ◽  
The Galaxy ◽  
Infrared Spectral ◽  
Shed Light

Thanks to its outstanding angular resolution, the Atacama Large Millimeter/submillimeter Array (ALMA) has recently unambiguously identified a population of optically dark galaxies with redshifts greater than z = 3, which play an important role in the cosmic star formation in massive galaxies. In this paper we study the properties of the six optically dark galaxies detected in the 69 arcmin2 GOODS-ALMA 1.1 mm continuum survey. While none of them are listed in the deepest H-band based CANDELS catalog in the GOODS-South field down to H = 28.16 AB, we were able to de-blend two of them from their bright neighbor and measure an H-band flux for them. We present the spectroscopic scan follow-up of five of the six sources with ALMA band 4. All are detected in the 2 mm continuum with signal-to-noise ratios higher than eight. One emission line is detected in AGS4 (νobs = 151.44 GHz with an S/N = 8.58) and AGS17 (νobs = 154.78 GHz with an S/N = 10.23), which we interpret in both cases as being due to the CO(6–5) line at zspecAGS4 = 3.556 and zspecAGS17 = 3.467, respectively. These redshifts match both the probability distribution of the photometric redshifts derived from the UV to near-infrared spectral energy distributions (SEDs) and the far-infrared SEDs for typical dust temperatures of galaxies at these redshifts. We present evidence that nearly 70% (4/6 of galaxies) of the optically dark galaxies belong to the same overdensity of galaxies at z ∼ 3.5. overdensity The most massive one, AGS24 (M⋆ = 1011.32−0.19+0.02 M⊙), is the most massive galaxy without an active galactic nucleus at z > 3 in the GOODS-ALMA field. It falls in the very center of the peak of the galaxy surface density, which suggests that the surrounding overdensity is a proto-cluster in the process of virialization and that AGS24 is the candidate progenitor of the future brightest cluster galaxy.

scholarly journals Helium abundances and its radial gradient from the spectra of H ii regions and ring nebulae of the Milky Way

2020 ◽  
Vol 496 (3) ◽  
pp. 2726-2742 ◽  
Author(s):  
J E Méndez-Delgado ◽  
C Esteban ◽  
J García-Rojas ◽  
K Z Arellano-Córdova ◽  
M Valerdi
Keyword(s):  
Milky Way ◽  
H Ii Regions ◽  
Abundance Gradient ◽  
Radial Gradient ◽  
Physical Conditions ◽  
The Galaxy ◽  
Ring Nebulae ◽  
Gaia Dr2 ◽  
Disc Galaxies ◽  
Weakly Dependent

ABSTRACT We determine the radial abundance gradient of helium in the disc of the Galaxy from published spectra of 19 H ii regions and ring nebulae surrounding massive O-type stars. We revise the Galactocentric distances of the objects considering Gaia DR2 parallaxes (Gaia Collaboration 2018) and determine the physical conditions and the ionic abundance of He+ in a homogeneous way, using between 3 and 10 He i recombination lines in each object. We estimate the total He abundance of the nebulae and its radial abundance gradient using four different ionization correction factor (ICF; He) schemes. The slope of the gradient is always negative and weakly dependent on the ICF(He) scheme, especially when only the objects with log(η) &lt; 0.9 are considered. The slope values go from −0.0078 to −0.0044 dex kpc−1, consistent with the predictions of chemical evolution models of the Milky Way and chemodynamical simulations of disc galaxies. Finally, we estimate the abundance deviations of He, O, and N in a sample of ring nebulae around Galactic Wolf–Rayet stars, finding a quite similar He overabundance of about +0.24 ± 0.11 dex in three stellar ejecta ring nebulae.

scholarly journals Polarized Optical and Infrared Emission from High Redshift Radio Galaxies

1994 ◽  
Vol 159 ◽  
pp. 470-470 ◽  
Author(s):  
Buell T. Jannuzi
Keyword(s):  
Active Galactic Nucleus ◽  
Rest Frame ◽  
Near Infrared ◽  
Uv Light ◽  
High Redshift ◽  
Radio Galaxies ◽  
Infrared Emission ◽  
Significant Component ◽  
Extended Radio ◽  
Polarized Emission

We have detected highly polarized (> 5%) optical and/or infrared emission (rest frame UV to near infrared) from 5 of the 8 high redshift radio galaxies (HZRG; z > 0.7) we have observed. There are now a total of 9 (out of 12 observed) HZRG known to be polarized in spatially integrated measurements (cf.). We have made images of the extended polarized emission from two radio galaxies (3C 265 and 3C 256). Detection of extended polarized emission from a HZRG has previously been reported for 3C 368. All of the existing polarization observations support the hypothesis that the “alignment effect” (the tendency of the extended UV light to be aligned with the extended radio emission, e.g.) is not solely produced by a burst of star formation, but contains a very significant component produced by the scattering of the light from a hidden active galactic nucleus (AGN). Our modeling of the frequency dependence of the polarized flux from 3C 265 suggests that the most probable scatterer is dust.

scholarly journals Interarm islands in the Milky Way – the one near the Cygnus spiral arm

2020 ◽  
Vol 494 (1) ◽  
pp. 1134-1142
Author(s):  
Jacques P Vallée
Keyword(s):  
Observational Data ◽  
Milky Way ◽  
Young Stars ◽  
H Ii Regions ◽  
Spiral Arms ◽  
The Galaxy ◽  
The One ◽  
Loop 2 ◽  
Perseus Arm ◽  
Spiral Arm

ABSTRACT This study extends to the structure of the Galaxy. Our main goal is to focus on the first spiral arm beyond the Perseus arm, often called the Cygnus arm or the ‘Outer Norma’ arm, by appraising the distributions of the masers near the Cygnus arm. The method is to employ masers whose trigonometric distances were measured with accuracy. The maser data come from published literature – see column 8 in Table 1 here, having been obtained via the existing networks (US VLBA, the Japanese VERA, the European VLBI, and the Australian LBA). The new results for Cygnus are split in two groups: those located near a recent CO-fitted global model spiral arm and those congregating within an ‘interarm island’ located halfway between the Perseus arm and the Cygnus arm. Next, we compare this island with other similar interarm objects near other spiral arms. Thus, we delineate an interarm island (6 × 2 kpc) located between the two long spiral arms (Cygnus and Perseus arms); this is reminiscent of the small ‘Local Orion arm’ (4 × 2 kpc) found earlier between the Perseus and Sagittarius arms and of the old ‘Loop’ (2 × 0.5 kpc) found earlier between the Sagittarius and Scutum arms. Various arm models are compared, based on observational data (masers, H II regions, H I gas, young stars, CO 1–0 gas).

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