scholarly journals High Resolution NIR Imaging of the Starburst Galaxy NGC 1808

1994 ◽  
Vol 159 ◽  
pp. 461-461
Author(s):  
L.E. Tacconi-Garman ◽  
A. Krabbe ◽  
A. Sternberg ◽  
R. Genzel
Keyword(s):  
Star Formation ◽  
Hot Spots ◽  
Active Sites ◽  
Near Infrared ◽  
Large Fraction ◽  
Line Emission ◽  
Far Infrared ◽  
Infrared Light ◽  
Continuum Emission ◽  
Starburst Galaxy

We report 0.6″ res. J, H, and K and 1.5″ res. imaging of 2.17 μm HI Brγ and 2.12 μm H2 1-0 S(1) line emission towards the nucleus of the starburst galaxy NGC 1808. In the K-band data we (partially) resolve the nucleus and see several small knots in the circumnuclear region. Further, our JHK continuum images show that a large fraction of the near infrared light in NGC 1808 is produced in young star forming clusters. The Brγ emission originates from a compact nuclear source and from several distinct emission knots in the circumnuclear region. These knots are spatially well correlated with a family of compact radio sources, but uncorrelated with the optical “hot spots”. We propose that the Brγ knots trace the actual sites of starburst activity, while the optical hot spots are just directions of low foreground extinction.We use our data together with radio and far-infrared continuum emission measurements to constrain the parameters of the individual starburst sites in NGC 1808. The data suggest that the starbursts are unsynchronized and prolonged (5 × 106–5 × 107 yrs). The star formation rates in the active sites range from ∼0.1 to ∼0.6 M⊙ yr−1, and the present rapid rate of star-formation in NGC 1808 can be maintained for at most another ∼7 × 107 yrs.Portions of this work are presently in press (Krabbe, Sternberg, and Genzel 1993), and a second paper is in preparation (Tacconi-Garman et al. 1993).

scholarly journals Near-Infrared View of the Nuclear Region of NGC 1808

1997 ◽  
Vol 159 ◽  
pp. 349-350
Author(s):  
J. K. Kotilainen
Keyword(s):  
Hot Spots ◽  
Near Infrared ◽  
Star Formation Rate ◽  
Hot Spot ◽  
Formation Rate ◽  
Line Emission ◽  
Continuum Emission ◽  
Starburst Galaxy ◽  
Nir Imaging ◽  
Red Supergiants

AbstractWe discuss NIR imaging of the starburst galaxy NGC 1808. The circumnuclear continuum emission shows no morphological change with wavelength and most of it is produced by an evolved bulge population, not by red supergiants or dust. The line emission arises from distinct hot spots. From comparison of Brγ and Hα fluxes, we derive extinction Av = 3–5 toward the hot spots. From modeling of the line and continuum luminosities, we derive a star-formation rate of 0.1–0.6 M⊙ yr–1 and SN rate ~ 0.4–11 × 10–3 yr–1 per hot spot. The age of the burst is 8–17 Myr for the hot spots and ~ 40 Myr for the nucleus. Finally, evidence for and against hidden Seyfert activity in NGC 1808 is discussed.

scholarly journals Radio properties of the OH megamaser galaxy IRAS 02524+2046

2020 ◽  
Vol 638 ◽  
pp. A78
Author(s):  
Hao Peng ◽  
Zhongzu Wu ◽  
Bo Zhang ◽  
Yongjun Chen ◽  
Xingwu Zheng ◽  
...  
Keyword(s):  
Flux Density ◽  
Spectral Index ◽  
Line Emission ◽  
Far Infrared ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Starburst Galaxy ◽  
Radio Flux ◽  
Vlbi Observations

We present results from VLBI observations of continuum and OH line emission in IRAS 02524+2046 as well as arcsecond-scale radio properties of this galaxy using VLA archive data. We found that there is no significant detection of radio continuum emission from VLBI observations. The arcsecond-scale radio images of this source show no clear extended emission. The total radio flux density at L and C bands are approximately 2.9 mJy and 1.0 mJy, respectively, which indicates a steep radio spectral index between the two bands. A steep spectral index, low brightness temperature, and high q-ratio (i.e., the far-infrared to the radio flux density), which are three critical indicators in the classification of radio activity in the nuclei of galaxies, are all consistent with the classification of this source as a starburst galaxy from its optical spectrum. The high-resolution line profile reveals that we detected both the 1665 MHz and 1667 MHz OH maser lines, which show two and three clear components, respectively. The channel maps show that the maser emission are distributed in a region of ∼210 pc × 90 pc. The detected maser components in different regions indicate similar double spectral features, which might be evidence that this galaxy is at a stage of major merger as seen from the optical morphology.

scholarly journals ALMA resolves molecular clouds in metal-poor Magellanic Bridge A

2020 ◽  
Vol 641 ◽  
pp. A97 ◽  
Author(s):  
M. T. Valdivia-Mena ◽  
M. Rubio ◽  
A. D. Bolatto ◽  
H. P. Saldaño ◽  
C. Verdugo
Keyword(s):  
Star Formation ◽  
Molecular Clouds ◽  
Dust Emission ◽  
Line Emission ◽  
Far Infrared ◽  
Continuum Emission ◽  
Molecular Gas ◽  
The North ◽  
Mass Conversion ◽  
North And South

Context. The Magellanic Bridge is a tidal feature located between the Magellanic Clouds, containing young stars formed in situ. Its proximity allows high-resolution studies of molecular gas, dust, and star formation in a tidal low-metallicity environment. Aims. Our goal is to characterize gas and dust emission in Magellanic Bridge A, the source with the highest 870 μm excess of emission found in single-dish surveys. Methods. Using the ALMA telescope including the Morita Array, we mapped a 3′ field of view centered on the Magellanic Bridge A molecular cloud, in 1.3 mm continuum emission and 12CO(2−1) line emission at subparsec resolution. This region was also mapped in continuum at 870 μm and in 12CO(2−1) line emission at ~6 pc resolution with the APEX telescope. To study its dust properties, we also use archival Herschel and Spitzer data. We combine the ALMA and APEX 12CO(2−1) line cubes to study the molecular gas emission. Results. Magellanic Bridge A breaks up into two distinct molecular clouds in dust and 12CO(2−1) emission, which we call North and South. Dust emission in the North source, according to our best parameters from fitting the far-infrared fluxes, is ≈3 K colder than in the South source in correspondence to its less developed star formation. Both dust sources present large submillimeter excesses in LABOCA data: according to our best fits the excess over the modified blackbody (MBB) fit to the Spitzer/Herschel continuum is E(870 μm) ~ 7 and E(870 μm) ~ 3 for the North and South sources, respectively. Nonetheless, we do not detect the corresponding 1.3 mm continuum with ALMA. Our limits are compatible with the extrapolation of the MBB fits, and therefore we cannot independently confirm the excess at this longer wavelength. The 12CO(2−1) emission is concentrated in two parsec-sized clouds with virial masses of around 400 and 700 M⊙. Their bulk volume densities are n(H2) ~ 0.7−2.6 × 103 cm−3, higher than typical bulk densities of Galactic molecular clouds. The 12CO luminosity to H2 mass conversion factor αCO is 6.5 and 15.3 M⊙ (K km s−1 pc2)−1 for the North and South clouds, calculated using their respective virial masses and 12CO(2−1) luminosities. Gas mass estimates from our MBB fits to dust emission yields masses M ~ 1.3 × 103 M⊙ and 2.9 × 103 M⊙ for North and South, respectively, a factor of ~4 higher than the virial masses we infer from 12CO.

5.21. Molecular gas in the center of the elliptical galaxy NGC759

1998 ◽  
Vol 184 ◽  
pp. 253-254
Author(s):  
T. Wiklind ◽  
F. Combes ◽  
C. Henkel ◽  
F. Wyrowski
Keyword(s):  
Star Formation ◽  
Uv Light ◽  
Elliptical Galaxy ◽  
Large Fraction ◽  
Dust Emission ◽  
Far Infrared ◽  
Elliptical Galaxies ◽  
Infrared Emission ◽  
Continuum Emission ◽  
Molecular Gas

Elliptical galaxies are traditionally defined as gas–free, inert stellar systems. Observations of continuum emission in the far–infrared (FIR) and sub–mm wavelength bands have, however, shown that a large fraction of all ellipticals, ~50% (Jura et al. 1987), contain a dust component. The infrared emission is due to warm dust, in many cases associated with star formation and/or weak AGN activity, while cold dust dominates the long wavelength continuum emission (e.g. Wiklind & Henkel 1995). Some elliptical galaxies also contain a molecular gas component, as seen through CO emission (Lees et al. 1991; Wiklind et al. 1995; Knapp & Rupen 1996). The dust and molecular gas are believed to be associated with each other, but it is not clear what powers the emission: star formation activity and/or AGN activity. Both the molecular gas mass and the FIR luminosity are on average lower in ellipticals than in spiral galaxies of similar luminosities. However, the LFIR/MH2 ratio is larger for the elliptical galaxies. If this ratio is a measure of the star formation efficiency, this suggests that gas is being used up more efficiently in elliptical galaxies than in normal spirals (e.g. Wiklind et al. 1995). Other possibilities is that the FIR dust emission is not only powered by UV–light from young stars, but from other sources as well, or that some dust is not spatially associated with the molecular gas.

scholarly journals Submillimeter Surveys at High Redshift

2002 ◽  
Vol 12 ◽  
pp. 469-472
Author(s):  
Amy J. Barger
Keyword(s):  
Star Formation ◽  
Near Infrared ◽  
High Redshift ◽  
Large Fraction ◽  
Far Infrared ◽  
Star Formation History ◽  
Infrared Galaxies ◽  
Small Admixture ◽  
Formation History ◽  
Ultraluminous Infrared Galaxies

AbstractDeep submillimeter (submm) surveys offer an unobscured view of dust-enshrouded star formation or AGN activity at high red-shifts. SCUBA observations above 2 mJy have resolved 20 – 30% of the far-infrared (FIR) background into discrete sources and have revealed the existence of a distant population of galaxies with properties similar to those of local ultraluminous infrared galaxies. A large fraction of the submm sources have extremely faint optical/near-infrared (NIR) counterparts and hence are inaccessible to optical spectroscopy. Millimetric redshift estimation places the submm population atz= 1 to 3. While the cumulative surface density of the submm sources is low, they are so luminous that if powered mainly by star formation, they dominate the high redshift star formation history. Recent combined SCUBA submm andChandrahard X-ray studies suggest that the majority of the submm sources are star formers with only a small admixture of obscured AGN.

scholarly journals Molecular gas in the Herschel-selected strongly lensed submillimeter galaxies at z ~ 2–4 as probed by multi-J CO lines

2017 ◽  
Vol 608 ◽  
pp. A144 ◽  
Author(s):  
C. Yang ◽  
A. Omont ◽  
A. Beelen ◽  
Y. Gao ◽  
P. van der Werf ◽  
...  
Keyword(s):  
Star Formation ◽  
High Redshift ◽  
Line Emission ◽  
Far Infrared ◽  
Molecular Gas ◽  
Kinetic Temperature ◽  
Large Area ◽  
Line Energy ◽  
Submillimeter Galaxies ◽  
Dust Mass

We present the IRAM-30 m observations of multiple-J CO (Jup mostly from 3 up to 8) and [C I](3P2 → 3P1) ([C I](2–1) hereafter) line emission in a sample of redshift ~2–4 submillimeter galaxies (SMGs). These SMGs are selected among the brightest-lensed galaxies discovered in the Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS). Forty-seven CO lines and 7 [C I](2–1) lines have been detected in 15 lensed SMGs. A non-negligible effect of differential lensing is found for the CO emission lines, which could have caused significant underestimations of the linewidths, and hence of the dynamical masses. The CO spectral line energy distributions (SLEDs), peaking around Jup ~ 5–7, are found to be similar to those of the local starburst-dominated ultra-luminous infrared galaxies and of the previously studied SMGs. After correcting for lensing amplification, we derived the global properties of the bulk of molecular gas in the SMGs using non-LTE radiative transfer modelling, such as the molecular gas density nH2 ~ 102.5–104.1 cm-3 and the kinetic temperature Tk  ~ 20–750 K. The gas thermal pressure Pth ranging from~105 K cm-3 to 106 K cm-3 is found to be correlated with star formation efficiency. Further decomposing the CO SLEDs into two excitation components, we find a low-excitation component with nH2 ~ 102.8–104.6 cm-3 and Tk  ~ 20–30 K, which is less correlated with star formation, and a high-excitation one (nH2 ~ 102.7–104.2 cm-3, Tk  ~ 60–400 K) which is tightly related to the on-going star-forming activity. Additionally, tight linear correlations between the far-infrared and CO line luminosities have been confirmed for the Jup ≥ 5 CO lines of these SMGs, implying that these CO lines are good tracers of star formation. The [C I](2–1) lines follow the tight linear correlation between the luminosities of the [C I](2–1) and the CO(1–0) line found in local starbursts, indicating that [C I] lines could serve as good total molecular gas mass tracers for high-redshift SMGs as well. The total mass of the molecular gas reservoir, (1–30) × 1010M⊙, derived based on the CO(3–2) fluxes and αCO(1–0) = 0.8 M⊙ ( K km s-1 pc2)-1, suggests a typical molecular gas depletion time tdep ~ 20–100 Myr and a gas to dust mass ratio δGDR ~ 30–100 with ~20%–60% uncertainty for the SMGs. The ratio between CO line luminosity and the dust mass L′CO/Mdust appears to be slowly increasing with redshift for high-redshift SMGs, which need to be further confirmed by a more complete SMG sample at various redshifts. Finally, through comparing the linewidth of CO and H2O lines, we find that they agree well in almost all our SMGs, confirming that the emitting regions of the CO and H2O lines are co-spatially located.

scholarly journals ALMA witnesses the assembly of first galaxies

2019 ◽  
Vol 15 (S352) ◽  
pp. 27-32
Author(s):  
Stefano Carniani
Keyword(s):  
Star Formation ◽  
Physical Properties ◽  
Rest Frame ◽  
Near Infrared ◽  
Far Infrared ◽  
Star Forming ◽  
Surrounding Environment ◽  
Infrared Surveys ◽  
Formation And Evolution ◽  
First Galaxies

AbstractCharacterising primeval galaxies entails the challenging goal of observing galaxies with modest star formation rates (SFR < 100 Mȯyr−1) and approaching the beginning of the reionisation epoch (z > 6). To date a large number of primeval galaxies have been identified thanks to deep near-infrared surveys. However, to further our understanding on the formation and evolution of such primeval objects, we must investigate their nature and physical properties through multi-band spectroscopic observations. Information on dust content, metallicity, interactions with the surrounding environment, and outflows can be obtained with ALMA observations of far-infrared (FIR) lines such as the [Cii] at 158 μm and [Oiii] at 88 μm. Here, we, thus, discuss the recent results unveiled by ALMA observations and present new [Cii] observations of BDF-3299, a star-forming galaxy at z = 7.1 showing a spatial and spectral offset between the rest-frame UV and the FIR lines emission.

scholarly journals Near-infrared monitoring of the accretion outburst in the massive young stellar object S255-NIRS3

2019 ◽  
Vol 72 (1) ◽  
Author(s):  
Mizuho Uchiyama ◽  
Takuya Yamashita ◽  
Koichiro Sugiyama ◽  
Tatsuya Nakaoka ◽  
Miho Kawabata ◽  
...  
Keyword(s):  
Light Curve ◽  
Near Infrared ◽  
Stellar Object ◽  
Young Stellar Objects ◽  
Infrared Light ◽  
Continuum Emission ◽  
Sudden Increase ◽  
Maser Emission ◽  
Young Stellar Object ◽  
Band Emission

Abstract We followed up the massive young stellar object S255-NIRS3 (= S255-IRS1b) during its recent accretion outburst event in the $K_{\rm s}$ band with Kanata/HONIR for four years after its burst and obtained a long-term light curve. This is the most complete near-infrared light curve of the S255-NIRS3 burst event that has ever been presented. The light curve showed a steep increase reaching a peak flux that was 3.4 mag brighter than the quiescent phase and then a relatively moderate year-scale fading until the last observation, similar to that of the accretion burst events such as EXors found in lower-mass young stellar objects. The behavior of the $K_{\rm s}$-band light curve is similar to that observed in 6.7 GHz class II methanol maser emission, with a sudden increase followed by moderate year-scale fading. However, the maser emission peaks appear 30–50 d earlier than that of the $K_{\rm s}$ band emission. The similarities confirmed that the origins of the maser emission and the $K_{\rm s}$-band continuum emission are common, as previously shown from other infrared and radio observations by Stecklum et al. (2016, Astronomer’s Telegram, 8732), Caratti o Garatti et al. (2017b, Nature Phys., 13, 276), and Moscadelli et al. (2017, A&A, 600, L8). However, the differences in energy transfer paths, such as the exciting/emitting/scattering structures, may cause the delay in the flux-peak dates.

scholarly journals SDSS-IV MaNGA: Bayesian analysis of the star formation history of low-mass galaxies in the local Universe

2020 ◽  
Vol 497 (4) ◽  
pp. 4753-4772
Author(s):  
Shuang Zhou ◽  
H J Mo ◽  
Cheng Li ◽  
Médéric Boquien ◽  
Graziano Rossi
Keyword(s):  
Star Formation ◽  
Near Infrared ◽  
Signal To Noise Ratio ◽  
Large Fraction ◽  
Stellar Mass ◽  
Star Formation History ◽  
Radial Dependence ◽  
High Signal ◽  
Full Spectrum ◽  
Low Mass

ABSTRACT We measure the star formation histories (SFHs) of a sample of low-mass galaxies with M* &lt; 109 M⊙ from the SDSS-IV MaNGA survey. The large number of IFU spectra for each galaxy are either combined to reach a high signal to noise ratio or used to investigate spatial variations. We use Bayesian inferences based on full spectrum fitting. Our analysis based on Bayesian evidence ratio indicates a strong preference for a model that allows the presence of an old stellar population, and that an improper model for the SFH can significantly underestimate the old population in these galaxies. The addition of near-infrared photometry to the constraining data can further distinguish between different SFH model families and significantly tighten the constraints on the mass fraction in the old population. On average more than half of the stellar mass in present-day low-mass galaxies formed at least 8 Gyr ago, while about 30 per cent within the past 4 Gyr. Satellite galaxies on average have formed their stellar mass earlier than central galaxies. The radial dependence of the SFH is quite weak. Our results suggest that most of the low-mass galaxies have an early episode of active star formation that produces a large fraction of their present stellar mass.

scholarly journals Investigations of dust heating in M81, M83 and NGC 2403 with Herschel and Spitzer

2011 ◽  
Vol 7 (S284) ◽  
pp. 97-100
Author(s):  
George J. Bendo ◽  
Keyword(s):  
Star Formation ◽  
Flux Density ◽  
Near Infrared ◽  
Dust Emission ◽  
Far Infrared ◽  
Spectral Energy ◽  
Star Forming ◽  
Star Forming Regions ◽  
Star Formation Activity ◽  
Density Ratios

AbstractWe use Herschel Space Observatory and Spitzer Space Telescope 70-500 μm data along with ground-based optical and near-infrared data to understand how dust heating in the nearby face-on spiral galaxies M81, M83, and NGC 2403 is affected by the starlight from all stars and by the radiation from star-forming regions. We find that 70/160 μm flux density ratios tend to be more strongly influenced by star-forming regions. However, the 250/350 and 350/500 μm micron flux density ratios are more strongly affected by the light from the total stellar populations, suggesting that the dust emission at > 250 μm originates predominantly from a component that is colder than the dust seen at <160 μm and that is relatively unaffected by star formation activity. We conclude by discussing the implications of this for modelling the spectral energy distributions of both nearby and more distant galaxies and for using far-infrared dust emission to trace star formation.

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