scholarly journals Big Three Dragons: A z = 7.15 Lyman-break galaxy detected in [O iii] 88 μm, [C ii] 158 μm, and dust continuum with ALMA

2019 ◽  
Vol 71 (4) ◽  
Author(s):  
Takuya Hashimoto ◽  
Akio K Inoue ◽  
Ken Mawatari ◽  
Yoichi Tamura ◽  
Hiroshi Matsuo ◽  
...  
Keyword(s):  
Star Formation ◽  
Rest Frame ◽  
Star Formation Rate ◽  
Hubble Space Telescope ◽  
Formation Rate ◽  
Ultra Violet ◽  
Absolute Magnitude ◽  
Continuum Emission ◽  
Starburst Galaxy ◽  
Dust Temperature

Abstract We present new ALMA observations and physical properties of a Lyman break galaxy at z = 7.15. Our target, B14-65666, has a bright ultra-violet (UV) absolute magnitude, MUV ≈ −22.4, and has been spectroscopically identified in Lyα with a small rest-frame equivalent width of ≈4 Å. A previous Hubble Space TElescope (HST) image has shown that the target is composed of two spatially separated clumps in the rest-frame UV. With ALMA, we have newly detected spatially resolved [O iii] 88 μm, [C ii] 158 μm, and their underlying dust continuum emission. In the whole system of B14-65666, the [O iii] and [C ii] lines have consistent redshifts of 7.1520 ± 0.0003, and the [O iii] luminosity, (34.4 ± 4.1) × 108 L⊙, is about three times higher than the [C ii] luminosity, (11.0 ± 1.4) × 108 L⊙. With our two continuum flux densities, the dust temperature is constrained to be Td ≈ 50–60 K under the assumption of a dust emissivity index of βd = 2.0–1.5, leading to a large total infrared luminosity of LTIR ≈ 1 × 1012 L⊙. Owing to our high spatial resolution data, we show that the [O iii] and [C ii] emission can be spatially decomposed into two clumps associated with the two rest-frame UV clumps whose spectra are kinematically separated by ≈200 km s−1. We also find these two clumps have comparable UV, infrared, [O iii], and [C ii] luminosities. Based on these results, we argue that B14-65666 is a starburst galaxy induced by a major merger. The merger interpretation is also supported by the large specific star formation rate (defined as the star formation rate per unit stellar mass), sSFR $= 260^{+119}_{-57}\:$Gyr−1, inferred from our SED fitting. Probably, a strong UV radiation field caused by intense star formation contributes to its high dust temperature and the [O iii]-to-[C ii] luminosity ratio.

scholarly journals Morphometry as a probe of the evolution of jellyfish galaxies: evidence of broadening in the surface brightness profiles of ram-pressure stripping candidates in the multicluster system A901/A902

2020 ◽  
Vol 500 (1) ◽  
pp. 40-53
Author(s):  
Fernanda Roman-Oliveira ◽  
Ana L Chies-Santos ◽  
Fabricio Ferrari ◽  
Geferson Lucatelli ◽  
Bruno Rodríguez Del Pino
Keyword(s):  
Star Formation ◽  
Surface Brightness ◽  
Quantitative Measurement ◽  
Star Formation Rate ◽  
Hubble Space Telescope ◽  
Formation Rate ◽  
Structural Evolution ◽  
Star Forming ◽  
Irregular Structures ◽  
Ram Pressure

ABSTRACT We explore the morphometric properties of a group of 73 ram-pressure stripping candidates in the A901/A902 multicluster system, at z∼ 0.165, to characterize the morphologies and structural evolution of jellyfish galaxies. By employing a quantitative measurement of morphometric indicators with the algorithm morfometryka on Hubble Space Telescope (F606W) images of the galaxies, we present a novel morphology-based method for determining trail vectors. We study the surface brightness profiles and curvature of the candidates and compare the results obtained with two analysis packages, morfometryka and iraf/ellipse on retrieving information of the irregular structures present in the galaxies. Our morphometric analysis shows that the ram-pressure stripping candidates have peculiar concave regions in their surface brightness profiles. Therefore, these profiles are less concentrated (lower Sérsic indices) than other star-forming galaxies that do not show morphological features of ram-pressure stripping. In combination with morphometric trail vectors, this feature could both help identify galaxies undergoing ram-pressure stripping and reveal spatial variations in the star formation rate.

scholarly journals SDSS J114818.18-013823.7: Forming Compact Dwarf Galaxy through the Dwarf-Dwarf Merger

2021 ◽  
Vol 7 (2) ◽  
pp. 49-57
Author(s):  
D. N. Chhatkuli ◽  
S. Paudel ◽  
A. K. Gautam ◽  
B. Aryal
Keyword(s):  
Star Formation ◽  
Emission Line ◽  
Star Formation Rate ◽  
Dwarf Galaxy ◽  
Formation Rate ◽  
Absolute Magnitude ◽  
Spectroscopic Properties ◽  
Normal Galaxies ◽  
Star Formation Activity ◽  
The Galaxy

We studied the spectroscopic properties of the low redshift (z = 0.0130) interacting dwarf galaxy SDSS J114818.18-013823.7. It is a compact galaxy of half-light radius 521 parsec. It’s r-band absolute magnitude is -16.71 mag. Using a publicly available optical spectrum from the Sloan Sky Survey data archive, we calculated star-formation rate, emission line metallicity, and dust extinction of the galaxy. Star formation rate (SFR) due to Hα is found to be 0.118 Mʘ year-1 after extinction correction. The emission-line metallicity, 12+log(O/H), is 8.13 dex. Placing these values in the scaling relation of normal galaxies, we find that SDSS J114818.18-013823.7 is a significant outlier from both size-magnitude relation and SFR-B-band absolute relation. Although SDSS J114818.18-013823.7 possess enhance rate of star-formation, the current star-formation activity can persist several Giga years in the future at the current place and it remains compact.

scholarly journals The SFR Efficiency of HI Gas in the Outskirts of Star Forming Galaxies

2016 ◽  
Vol 11 (S321) ◽  
pp. 360-362
Author(s):  
Marc Rafelski
Keyword(s):  
Star Formation ◽  
Atomic Hydrogen ◽  
Rest Frame ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Hydrogen Gas ◽  
Star Forming ◽  
Uv Emission ◽  
Atomic Gas

AbstractIn order to understand the origin of the decreased star formation rate (SFR) efficiency of neutral atomic hydrogen gas measured in Damped Lyα Systems (DLAs) at z ~ 3, we measure the SFR efficiency of atomic gas at z ~ 1, z ~ 2, and z ~ 3 around star-forming galaxies. We create galaxy stacks in these three redshift bins, and measure the SFR efficiency by combining DLA absorber statistics with the observed rest-frame UV emission in the galaxies’ outskirts. We find that the SFR efficiency of Hi gas is ~ 3% of that predicted by the KS relation. We find no significant evolution in the SFR efficiency with redshift, although simulations and models predict a decreasing SFR efficiency with decreasing metallicity and thus with increasing redshift. We discuss possible explanations for this decreased efficiency without an evolution with redshift.

scholarly journals Evolution of the Luminosity Function, Star Formation Rate, Morphology, and Size of Star‐forming Galaxies Selected at Rest‐Frame 1500 and 2800 A

2007 ◽  
Vol 654 (1) ◽  
pp. 172-185 ◽  
Author(s):  
Tomas Dahlen ◽  
Bahram Mobasher ◽  
Mark Dickinson ◽  
Henry C. Ferguson ◽  
Mauro Giavalisco ◽  
...  
Keyword(s):  
Star Formation ◽  
Luminosity Function ◽  
Rest Frame ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Star Forming

scholarly journals A spectroscopic study of the low redshift dwarf galaxy SDSS J134326.99+431118.7 to calculate star formation rate

BIBECHANA ◽  
2021 ◽  
Vol 18 (1) ◽  
pp. 100-107
Author(s):  
Daya Nidhi Chhatkuli ◽  
Sanjaya Paudel ◽  
Binil Aryal
Keyword(s):  
Star Formation ◽  
Spectroscopic Study ◽  
Emission Line ◽  
Star Formation Rate ◽  
Dwarf Galaxy ◽  
Formation Rate ◽  
Flux Ratio ◽  
Starburst Galaxy ◽  
Characteristic Lines ◽  
The Galaxy

We present a spectroscopic study of an interacting emission-line dwarf galaxy SDSS J134326.99+431118.7. We analyzed eight-strong emission lines of wavelength in a range of 3902.1Å to 6619.1Å. Among them, the strongest emission line is OIII, with an intensity of 1043.6 x 10-17 erg/s/cm2/Å. These characteristic lines show a perfect Gaussian fit with a coefficient of regression greater than 98%, where the derived full width half maximum (FWHM) is less than 3.8 Å. The line ratio between Ha  and Hb, (Ha/ Hb), is  2.73. This suggests that the galaxy is a starburst galaxy. Star Formation Rate (SFR) of the galaxy derived from Ha  emission line flux is 0.019  and emission line metallicity derived from flux ratio between NII and Ha is 7.85 dex. These morphological and physical properties of SDSSJ134326.99+431118.7 are very similar to those of a typical Blue Compact Dwarf (BCD) galaxy. We conclude that we have presented another evidence of forming a BCD-type galaxy through a merger. BIBECHANA 18 (2021) 100-107

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 Deciphering the radio star formation correlation on kpc scales

2020 ◽  
Vol 633 ◽  
pp. A144 ◽  
Author(s):  
B. Vollmer ◽  
M. Soida ◽  
R. Beck ◽  
M. Powalka
Keyword(s):  
Magnetic Field ◽  
Star Formation ◽  
Spiral Galaxies ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Cosmic Ray ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Smoothing Kernel ◽  
The Magnetic Field

One of the tightest correlations in astronomy is the relation between the integrated radio continuum and the far-infrared (FIR) emission. Within nearby galaxies, variations in the radio–FIR correlation have been observed, mainly because the cosmic ray electrons migrate before they lose their energy via synchrotron emission or escape. The major cosmic-ray electron transport mechanisms within the plane of galactic disks are diffusion, and streaming. A predicted radio continuum map can be obtained by convolving the map of cosmic-ray electron sources, represented by that of the star formation, with adaptive Gaussian and exponential kernels. The ratio between the smoothing lengthscales at 6 cm and 20 cm can be used to determine, between diffusion and streaming, which is the dominant transport mechanism. The dependence of the smoothing lengthscale on the star formation rate bears information on the dependence of the magnetic field strength, or the ratio between the ordered and turbulent magnetic field strengths on star formation. Star formation maps of eight rather face-on local and Virgo cluster spiral galaxies were constructed from Spitzer and Herschel infrared and GALEX UV observations. These maps were convolved with adaptive Gaussian and exponential smoothing kernels to obtain model radio continuum emission maps. It was found that in asymmetric ridges of polarized radio continuum emission, the total power emission is enhanced with respect to the star formation rate. At a characteristic star formation rate of $ \dot{\Sigma}_*=8 \times 10^{-3}\,M_{\odot} $ yr−1 kpc−2, the typical lengthscale for the transport of cosmic-ray electrons is l = 0.9 ± 0.3 kpc at 6 cm, and l = 1.8 ± 0.5 kpc at 20 cm. Perturbed spiral galaxies tend to have smaller lengthscales. This is a natural consequence of the enhancement of the magnetic field caused by the interaction. The discrimination between the two cosmic-ray electron transport mechanisms, diffusion, and streaming is based on (i) the convolution kernel (Gaussian or exponential); (ii) the dependence of the smoothing kernel on the local magnetic field, and thus on the local star formation rate; (iii) the ratio between the two smoothing lengthscales via the frequency dependence of the smoothing kernel, and (iv) the dependence of the smoothing kernel on the ratio between the ordered and the turbulent magnetic field. Based on our empirical results, methods (i) and (ii) cannot be used to determine the cosmic ray transport mechanism. Important asymmetric large-scale residuals and a local dependence of the smoothing length on Bord/Bturb are most probably responsible for the failure of methods (i) and (ii), respectively. On the other hand, the classifications based on l6 cm/l20 cm (method iii) and Bord/Bturb (method iv), are well consistent and complementary. We argue that in the six Virgo spiral galaxies, the turbulent magnetic field is globally enhanced in the disk. Therefore, the regions where the magnetic field is independent of the star formation rate are more common. In addition, Bord/Bturb decreases, leading to a diffusion lengthscale that is smaller than the streaming lengthscale. Therefore, cosmic ray electron streaming dominates in most of the Virgo spiral galaxies.

scholarly journals UV and Lyα luminosity functions of galaxies and star formation rate density at the end of HI reionization from the VIMOS UltraDeep Survey (VUDS)

2020 ◽  
Vol 634 ◽  
pp. A97 ◽  
Author(s):  
Y. Khusanova ◽  
O. Le Fèvre ◽  
P. Cassata ◽  
O. Cucciati ◽  
B. C. Lemaux ◽  
...  
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Excellent Agreement ◽  
Luminosity Function ◽  
Rest Frame ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Selection Function ◽  
Star Forming ◽  
Luminosity Functions

Context. The star formation rate density (SFRD) evolution presents an area of great interest in the studies of galaxy evolution and reionization. The current constraints of SFRD at z >  5 are based on the rest-frame UV luminosity functions with the data from photometric surveys. The VIMOS UltraDeep Survey (VUDS) was designed to observe galaxies at redshifts up to ∼6 and opened a window for measuring SFRD at z >  5 from a spectroscopic sample with a well-controlled selection function. Aims. We establish a robust statistical description of the star-forming galaxy population at the end of cosmic HI reionization (5.0 ≤ z ≤ 6.6) from a large sample of 49 galaxies with spectroscopically confirmed redshifts. We determine the rest-frame UV and Lyα luminosity functions and use them to calculate SFRD at the median redshift of our sample z = 5.6. Methods. We selected a sample of galaxies at 5.0 ≤ zspec ≤ 6.6 from the VUDS. We cleaned our sample from low redshift interlopers using ancillary photometric data. We identified galaxies with Lyα either in absorption or in emission, at variance with most spectroscopic samples in the literature where Lyα emitters (LAE) dominate. We determined luminosity functions using the 1/Vmax method. Results. The galaxies in this redshift range exhibit a large range in their properties. A fraction of our sample shows strong Lyα emission, while another fraction shows Lyα in absorption. UV-continuum slopes vary with luminosity, with a large dispersion. We find that star-forming galaxies at these redshifts are distributed along the main sequence in the stellar mass vs. SFR plane, described with a slope α = 0.85 ± 0.05. We report a flat evolution of the specific SFR compared to lower redshift measurements. We find that the UV luminosity function is best reproduced by a double power law, while a fit with a Schechter function is only marginally inferior. The Lyα luminosity function is best fitted with a Schechter function. We derive a logSFRDUV(M⊙ yr−1 Mpc−3) = −1.45+0.06−0.08 and logSFRDLyα(M⊙ yr−1 Mpc−3) = −1.40+0.07−0.08. The SFRD derived from the Lyα luminosity function is in excellent agreement with the UV-derived SFRD after correcting for IGM absorption. Conclusions. Our new SFRD measurements at a mean redshift of z = 5.6 are ∼0.2 dex above the mean SFRD reported in Madau & Dickinson (2014, ARA&A, 52, 415), but in excellent agreement with results from Bouwens et al. (2015a, ApJ, 803, 34). These measurements confirm the steep decline of the SFRD at z >  2. The bright end of the Lyα luminosity function has a high number density, indicating a significant star formation activity concentrated in the brightest LAE at these redshifts. LAE with equivalent width EW > 25 Å contribute to about 75% of the total UV-derived SFRD. While our analysis favors low dust content in 5.0 <  z <  6.6, uncertainties on the dust extinction correction and associated degeneracy in spectral fitting will remain an issue, when estimating the total SFRD until future surveys extending spectroscopy to the NIR rest-frame spectral domain, such as with JWST.

scholarly journals A LOFAR-IRAS cross-match study: the far-infrared radio correlation and the 150 MHz luminosity as a star-formation rate tracer

2019 ◽  
Vol 631 ◽  
pp. A109 ◽  
Author(s):  
L. Wang ◽  
F. Gao ◽  
K. J. Duncan ◽  
W. L. Williams ◽  
M. Rowan-Robinson ◽  
...  
Keyword(s):  
Star Formation ◽  
Rest Frame ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Value Added ◽  
Far Infrared ◽  
Star Forming ◽  
Dust Extinction ◽  
Best Fit ◽  
Cross Match

Aims. We aim to study the far-infrared radio correlation (FIRC) at 150 MHz in the local Universe (at a median redshift ⟨z⟩∼0.05) and improve the use of the rest-frame 150 MHz luminosity, L150, as a star-formation rate (SFR) tracer, which is unaffected by dust extinction. Methods. We cross-match the 60 μm selected Revised IRAS Faint Source Survey Redshift (RIFSCz) catalogue and the 150 MHz selected LOFAR value-added source catalogue in the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) Spring Field. We estimate L150 for the cross-matched sources and compare it with the total infrared (IR) luminosity, LIR, and various SFR tracers. Results. We find a tight linear correlation between log L150 and log LIR for star-forming galaxies, with a slope of 1.37. The median qIR value (defined as the logarithm of the LIR to L150 ratio) and its rms scatter of our main sample are 2.14 and 0.34, respectively. We also find that log L150 correlates tightly with the logarithm of SFR derived from three different tracers, i.e., SFRHα based on the Hα line luminosity, SFR60 based on the rest-frame 60 μm luminosity and SFRIR based on LIR, with a scatter of 0.3 dex. Our best-fit relations between L150 and these SFR tracers are, log L150 (L⊙) = 1.35(±0.06) × log SFRHα (M⊙ yr−1) + 3.20(±0.06), log L150 (L⊙) = 1.31(±0.05) × log SFR60 (M⊙ yr−1) + 3.14(±0.06), and log L150 (L⊙) = 1.37 (±0.05) × log SFRIR (M⊙ yr−1) + 3.09(±0.05), which show excellent agreement with each other.

scholarly journals Low-redshift quasars in the SDSS Stripe 82 – II. Associated companion galaxies and signature of star formation

2020 ◽  
Vol 501 (1) ◽  
pp. 419-439
Author(s):  
M B Stone ◽  
D Bettoni ◽  
R Falomo ◽  
J K Kotilainen ◽  
K Karhunen ◽  
...  
Keyword(s):  
Star Formation ◽  
Emission Line ◽  
Large Scale ◽  
Strong Influence ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Host Galaxy ◽  
Starburst Galaxy ◽  
Published Paper ◽  
Larger Sample

ABSTRACT We present optical spectroscopy of the close companions of 22 low-redshift (z &lt; 0.5) quasars (QSO) selected from a larger sample of QSO in the SDSS Stripe82 region for which both the host galaxy and the large-scale environments have been investigated in our previous work. The new observations extend the number of QSO studied in our previous paper on close companion galaxies of 12 quasars. Our analysis here covers all 34 quasars from both this work and the previously published paper. We find that half of them (15 QSO; ∼44 per cent) have at least one associated galaxy. Many (12 galaxies; ∼67 per cent) of the associated companions exhibit [O ii] 3727 Å emission line as signature of recent star formation. The star formation rate (SFR) of these galaxies is modest (median SFR ∼ 4.3 M⊙ yr−1). For eight QSO, we are also able to detect the starlight of the host galaxy from which three have a typical spectrum of a post-starburst galaxy. Our results suggest that quasars do not have a strong influence on the star formation of their companion galaxies.

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