scholarly journals The metallicity–redshift relations for emission-line SDSS galaxies: examination of the dependence on the star formation rate

2013 ◽  
Vol 432 (2) ◽  
pp. 1217-1230 ◽  
Author(s):  
L. S. Pilyugin ◽  
M. A. Lara-López ◽  
E. K. Grebel ◽  
C. Kehrig ◽  
I. A. Zinchenko ◽  
...  
Keyword(s):  
Star Formation ◽  
Emission Line ◽  
Star Formation Rate ◽  
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 A cautionary tale of attenuation in star-forming regions

2020 ◽  
Vol 494 (4) ◽  
pp. 4751-4770 ◽  
Author(s):  
Mallory Molina ◽  
Nikhil Ajgaonkar ◽  
Renbin Yan ◽  
Robin Ciardullo ◽  
Caryl Gronwall ◽  
...  
Keyword(s):  
Star Formation ◽  
Emission Line ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Dust Content ◽  
Physical Parameters ◽  
Star Forming ◽  
Total Dust ◽  
Star Forming Regions ◽  
Field Unit

ABSTRACT The attenuation of light from star-forming galaxies is correlated with a multitude of physical parameters including star formation rate, metallicity and total dust content. This variation in attenuation is even more evident on kiloparsec scales, which is the relevant size for many current spectroscopic integral field unit surveys. To understand the cause of this variation, we present and analyse Swift/UVOT near-UV (NUV) images and SDSS/MaNGA emission-line maps of 29 nearby (z < 0.084) star-forming galaxies. We resolve kiloparsec-sized star-forming regions within the galaxies and compare their optical nebular attenuation (i.e. the Balmer emission line optical depth, $\tau ^{l}_{B}\equiv \tau _{\textrm {H}\beta }-\tau _{\textrm {H}\alpha }$) and NUV stellar continuum attenuation (via the NUV power-law index, β) to the attenuation law described by Battisti et al. We show the data agree with that model, albeit with significant scatter. We explore the dependence of the scatter of the β–$\tau ^{l}_{B}$ measurements from the star-forming regions on different physical parameters, including distance from the nucleus, star formation rate and total dust content. Finally, we compare the measured $\tau ^{l}_{B}$ and β values for the individual star-forming regions with those of the integrated galaxy light. We find a strong variation in β between the kiloparsec scale and the larger galaxy scale that is not seen in $\tau ^{l}_{B}$. We conclude that the sightline dependence of UV attenuation and the reddening of β due to the light from older stellar populations could contribute to the scatter in the β–$\tau ^{l}_{B}$ relation.

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 The VANDELS survey: the role of ISM and galaxy physical properties in the escape of Lyα emission in z ∼ 3.5 star-forming galaxies

2019 ◽  
Vol 631 ◽  
pp. A19 ◽  
Author(s):  
F. Marchi ◽  
L. Pentericci ◽  
L. Guaita ◽  
M. Talia ◽  
M. Castellano ◽  
...  
Keyword(s):  
Star Formation ◽  
Physical Properties ◽  
Emission Line ◽  
Column Density ◽  
Star Formation Rate ◽  
Spectral Energy Distribution ◽  
Formation Rate ◽  
Stellar Mass ◽  
Dust Extinction

Aims. We wish to investigate the physical properties of a sample of Lyα emitting galaxies in the VANDELS survey, with particular focus on the role of kinematics and neutral hydrogen column density in the escape and spatial distribution of Lyα photons. Methods. From all the Lyα emitting galaxies in the VANDELS Data Release 2 at 3.5 ≲ z ≲ 4.5, we selected a sample of 52 galaxies that also have a precise systemic redshift determination from at least one nebular emission line (HeII or CIII]). For these galaxies, we derived different physical properties (stellar mass, age, dust extinction, and star formation rate) from spectral energy distribution (SED) fitting of the exquisite multiwavelength photometry available in the VANDELS fields, using the dedicated spectral modeling tool BEAGLE and the UV β slope from the observed photometry. We characterized the Lyα emission in terms of kinematics, equivalent width (EW), full width at half-maximum, and spatial extension and then estimated the velocity of the neutral outflowing gas. The ultra-deep VANDELS spectra (up to 80 h on-source integration) enable this for individual galaxies without the need to rely on stacks. We then investigated the correlations between the Lyα properties and the other measured properties to study how they affect the shape and intensity of Lyα emission. Results. We reproduce some of the well-known correlations between Lyα EW and stellar mass, dust extinction, and UV β slope, in the sense that the emission line appears brighter in galaxies with lower mass that are less dusty and bluer. We do not find any correlation with the SED-derived star formation rate, while we find that galaxies with brighter Lyα tend to be more compact in both UV and in Lyα. Our data reveal an interesting correlation between the Lyα velocity offset and the shift of the interstellar absorption lines with respect to the systemic redshift, observed for the first time at high redshifts: galaxies with higher interstellar medium (ISM) outflow velocities show smaller Lyα velocity shifts. We interpret this relation in the context of the shell-model scenario, where the velocity of the ISM and the HI column density contribute together in determining the Lyα kinematics. In support to our interpretation, we observe that galaxies with high HI column densities have much more extended Lyα spatial profiles; this is a sign of increased scattering. However, we do not find any evidence that the HI column density is related to any other physical properties of the galaxies, although this might be due in part to the limited range of parameters that our sample spans.

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 < 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.

scholarly journals The evolution of the equivalent width of the Hα emission line and specific star formation rate in star-forming galaxies at 1 < z < 5

2016 ◽  
Vol 460 (4) ◽  
pp. 3587-3597 ◽  
Author(s):  
E. Mármol-Queraltó ◽  
R. J. McLure ◽  
F. Cullen ◽  
J. S. Dunlop ◽  
A. Fontana ◽  
...  
Keyword(s):  
Star Formation ◽  
Emission Line ◽  
Equivalent Width ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Star Forming ◽  
Hα Emission

scholarly journals J-PLUS: Measuring Hα emission line fluxes in the nearby universe

2019 ◽  
Vol 622 ◽  
pp. A180 ◽  
Author(s):  
R. Logroño-García ◽  
G. Vilella-Rojo ◽  
C. López-Sanjuan ◽  
J. Varela ◽  
K. Viironen ◽  
...  
Keyword(s):  
Star Formation ◽  
Emission Line ◽  
Star Formation Rate ◽  
Narrow Band ◽  
Formation Rate ◽  
Photometric Data ◽  
Star Forming ◽  
Spatially Resolved ◽  
Band Filter ◽  
Narrow Band Filter

In this paper we aim to validate a methodology designed to obtain Hα emission line fluxes from J-PLUS photometric data. J-PLUS is a multi narrow-band filter survey carried out with the 2 deg2 field of view T80Cam camera, mounted on the JAST/T80 telescope in the OAJ, Teruel, Spain. The information of the twelve J-PLUS bands, including the J0660 narrow-band filter located at rest-frame Hα, is used over the first 42 deg2 observed to retrieve de-reddened and [NII] decontaminated Hα emission line fluxes of 46 star-forming regions with previous SDSS and/or CALIFA spectroscopic information. The agreement between the J-PLUS Hα fluxes and those obtained with spectroscopic data is remarkable, finding a median comparison ratio with a scatter of $ \mathcal{R}\,{=}\,F^{\mathrm{J-PLUS}}_{\mathrm{H\alpha}}/F^{\mathrm{spec}}_{\mathrm{H\alpha}}\,{=}\,1.05\,{\pm}\,0.25 $. This demonstrates that it is possible to retrieve reliable Hα emission line fluxes from J-PLUS photometric data. With an expected area of thousands of square degrees upon completion, the J-PLUS dataset will allow the study of several star formation science cases in the nearby universe, as the spatially resolved star formation rate of nearby galaxies at z  ≤  0.015, and how it is influenced by the environment, morphology, stellar mass, and nuclear activity. As an illustrative example, the close pair of interacting galaxies NGC 3994 and NGC 3995 is analysed, finding an enhancement of the star formation rate not only in the centre, but also in outer parts of the disk of NGC 3994.

Wolf-Rayet Stars as Tracers of the Recent History of the Star Formation Rate

1994 ◽  
Vol 159 ◽  
pp. 451-451
Author(s):  
G. Meynet
Keyword(s):  
Star Formation ◽  
Emission Line ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Mass Function ◽  
Emission Feature ◽  
Initial Mass Function ◽  
Order Of Magnitude ◽  
History Of ◽  
Conversion Formula

Recently Vacca & Conti (1992) have measured the ratio of the luminosity in the broad He II λ4686 emission feature to that in the Hβ emission line in fourteen starburst galaxies. They related these luminosity ratios to the relative numbers of Wolf-Rayet (type WNL) to O-type stars in these galaxies (higher is the ratio L(λ4686)/L(Hβ), higher is NWNL/NO). They found that in general the number ratios are an order of magnitude larger than those expected in region of constant star formation rate. On Fig. 1 the predicted line ratios of our starbursts models (instantaneous burst of star formation at time t = 0; initial mass function dN/dM = CM−2; stellar models from Meynet et al. 1993; conversion formula between the line ratios and the number ratios of WNL to O-type stars given by Vacca & Conti 1992, with η = 1) are compared with the observed values given by these authors. This figure shows that a starburst taking place about 2–3 millions years ago can account for the high observed values of L(λ4686)/L(Hβ). One sees that the effects of the age of the burst (i.e. the time elapsed since the burst) and of the metallicity are quite important. It is the hope that in a next future, it will be possible on the base of this kind of luminosity ratios to disentangle the various effects influencing the WR population resulting from a starburst.

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