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 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 Study of Star Formation Rate and Metallicity of an Interacting Dwarf Galaxy NGC 2604

2020 ◽  
Vol 25 (2) ◽  
pp. 55-60
Author(s):  
Daya Nidhi Chhatkuli ◽  
Sanjaya Paudel ◽  
Binil Aryal
Keyword(s):  
Star Formation ◽  
Star Formation Rate ◽  
Dwarf Galaxy ◽  
Formation Rate ◽  
Emission Lines ◽  
A Value ◽  
Characteristic Emission ◽  
Characteristic Lines ◽  
The Galaxy ◽  
Hα Emission

We present a study of the Sloan Digital all Sky Survey Data Release 12 (SDSS DR12) optical spectra of an interacting dwarf galaxy NGC 2604 that has redshift 0.0069. Thirteen characteristic emission lines were identified in the wavelength range of 3885 Å to 6742 Å, the strongest line was due to Hα emission with a value of emission-line flux 1538.8 erg/s/cm2/Å. The other twelve emission lines were observed because of OI doublet, Hβ, Hγ, Hδ, OIII doublet, HeI, SII doublet and NII doublet transitions. Eleven characteristic lines agreed perfectly with the Gaussian distribution with greater than 99.9 % coefficient of regression. However, full-width half maximum (FWHM) was found to be less than 5 Å. No absorption metallic lines were observed in the spectra which indicates that the galaxy was either newly formed. The line metallicity of the galaxy was found to be 8.4 dex and the extinction coefficient was 0.2134. The star formation rate due to Hα emission after extinction correction was found to be 0.0927 Mʘ year -1 which is almost double of the value (0.057 Mʘ year -1) before correction.

scholarly journals Impact of relativistic jets on the star formation rate: A turbulence-regulated framework

2021 ◽  
Author(s):  
Ankush Mandal ◽  
Dipanjan Mukherjee ◽  
Christoph Federrath ◽  
Nicole P H Nesvadba ◽  
Geoffrey V Bicknell ◽  
...  
Keyword(s):  
Star Formation ◽  
Velocity Dispersion ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Star Forming ◽  
Radio Jets ◽  
Star Formation Activity ◽  
The Galaxy ◽  
Individual Star ◽  
The Impact

Abstract We apply a turbulence-regulated model of star formation to calculate the star formation rate (SFR) of dense star-forming clouds in simulations of jet-ISM interactions. The method isolates individual clumps and accounts for the impact of virial parameter and Mach number of the clumps on the star formation activity. This improves upon other estimates of the SFR in simulations of jet–ISM interactions, which are often solely based on local gas density, neglecting the impact of turbulence. We apply this framework to the results of a suite of jet-ISM interaction simulations to study how the jet regulates the SFR both globally and on the scale of individual star-forming clouds. We find that the jet strongly affects the multi-phase ISM in the galaxy, inducing turbulence and increasing the velocity dispersion within the clouds. This causes a global reduction in the SFR compared to a simulation without a jet. The shocks driven into clouds by the jet also compress the gas to higher densities, resulting in local enhancements of the SFR. However, the velocity dispersion in such clouds is also comparably high, which results in a lower SFR than would be observed in galaxies with similar gas mass surface densities and without powerful radio jets. We thus show that both local negative and positive jet feedback can occur in a single system during a single jet event, and that the star-formation rate in the ISM varies in a complicated manner that depends on the strength of the jet-ISM coupling and the jet break-out time-scale.

scholarly journals The Sagittarius Dwarf Galaxy Survey (SDGS): Constraints on the Star Formation History of the Sgr dSph

1999 ◽  
Vol 192 ◽  
pp. 121-128
Author(s):  
M. Bellazzini ◽  
F. R. Ferraro ◽  
R. Buonanno
Keyword(s):  
Star Formation ◽  
Star Formation Rate ◽  
Dwarf Galaxy ◽  
Formation Rate ◽  
Star Formation History ◽  
Full Potential ◽  
Chemical Enrichment ◽  
Formation History ◽  
The Galaxy ◽  
History Of

The main characteristics of a wide photometric survey of the Sgr dwarf spheroidal galaxy are briefly presented. V and I photometry has been obtained for ~90000 stars toward Sgr and for ~9000 stars in a region devoid of Sgr stars (for decontamination purposes).The full potential of this large database is far from being completely explored. Here we present only preliminary results from the analysis of statistically decontaminated Color Magnitude Diagrams, trying to set a scheme of the Star Formation History of the Sgr Galaxy. A scenario is proposed in which star formation in Sgr began very early and lasted for several Gyr, with progressive chemical enrichment of the Inter-Stellar Medium (ISM). Nearly 8 Gyr ago the star formation rate abruptly decreased, perhaps in coincidence with the event that led to the gas depletion of the galaxy. A very small rate of star formation continued until relatively recent times (~ 1 Gyr ago).

scholarly journals Cosmological simulations of low-mass galaxies: some potential issues

2010 ◽  
Vol 6 (S270) ◽  
pp. 503-506
Author(s):  
Pedro Colín ◽  
Vladimir Avila-Reese ◽  
Octavio Valenzuela
Keyword(s):  
Star Formation ◽  
Adaptive Mesh Refinement ◽  
Mass Fraction ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Mesh Refinement ◽  
Adaptive Mesh ◽  
Stellar Mass ◽  
The Galaxy ◽  
Low Mass

AbstractCosmological Adaptive Mesh Refinement simulations are used to study the specific star formation rate (sSFR=SSF/Ms) history and the stellar mass fraction, fs=Ms/MT, of small galaxies, total masses MT between few × 1010 M⊙ to few ×1011 M⊙. Our results are compared with recent observational inferences that show the so-called “downsizing in sSFR” phenomenon: the less massive the galaxy, the higher on average is its sSFR, a trend seen at least since z ~ 1. The simulations are not able to reproduce this phenomenon, in particular the high inferred values of sSFR, as well as the low values of fs constrained from observations. The effects of resolution and sub-grid physics on the SFR and fs of galaxies are discussed.

scholarly journals Satellites and central galaxies in SDSS: the influence of interactions on their properties

2020 ◽  
Vol 501 (1) ◽  
pp. 1046-1058
Author(s):  
Valeria Mesa ◽  
Sol Alonso ◽  
Georgina Coldwell ◽  
Diego García Lambas ◽  
J L Nilo Castellon
Keyword(s):  
Star Formation ◽  
Stellar Population ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Control Sample ◽  
Stellar Populations ◽  
Control Sets ◽  
Central Galaxy ◽  
Star Formation Activity ◽  
Projected Distance

ABSTRACT We use SDSS-DR14 to construct a sample of galaxy systems consisting of a central object and two satellites. We adopt projected distance and radial velocity difference criteria and impose an isolation criterion to avoid membership in larger structures. We also classify the interaction between the members of each system through a visual inspection of galaxy images, finding ${\sim}80{{\ \rm per\ cent}}$ of the systems lack evidence of interactions whilst the remaining ${\sim}20{{\ \rm per\ cent}}$ involve some kind of interaction, as inferred from their observed distorted morphology. We have considered separately, samples of satellites and central galaxies, and each of these samples were tested against suitable control sets to analyse the results. We find that central galaxies showing signs of interactions present evidence of enhanced star formation activity and younger stellar populations. As a counterpart, satellite samples show these galaxies presenting older stellar populations with a lower star formation rate than the control sample. The observed trends correlate with the stellar mass content of the galaxies and with the projected distance between the members involved in the interaction. The most massive systems are less affected since they show no star formation excess, possibly due to their more evolved stage and less gas available to form new stars. Our results suggest that it is arguably a transfer of material during interactions, with satellites acting as donors to the central galaxy. As a consequence of the interactions, satellite stellar population ages rapidly and new bursts of star formation may frequently occur in the central galaxy.

Extreme variations in star formation activity in the first galaxies

2019 ◽  
Vol 15 (S341) ◽  
pp. 226-230
Author(s):  
Christian Binggeli ◽  
Erik Zackrisson ◽  
Xiangcheng Ma ◽  
Akio K. Inoue ◽  
Anton Vikaeus ◽  
...  
Keyword(s):  
Star Formation ◽  
Rest Frame ◽  
High Redshift ◽  
Formation Rate ◽  
High Redshift Galaxies ◽  
James Webb Space Telescope ◽  
Star Formation Activity ◽  
The Galaxy ◽  
First Galaxies ◽  
Star Formation Histories

AbstractRecently, spectroscopic detections of O[III] 88 μm and Ly-α emission lines from the z ≍ 9.1 galaxy MACS1149-JD1 have been presented, and with these, some interesting properties of this galaxy were uncovered. One such property is that MACS1149-JD1 exhibits a significant Balmer break at around rest-frame 4000 Å, which may indicate that the galaxy has experienced large variations in star formation rate prior to z ∼ 9, with a rather long period of low star formation activity. While some simulations predict large variations in star formation activity in high-redshift galaxies, it is unclear whether the simulations can reproduce the kind of variations seen in MACS1149-JD1. Here, we utilize synthetic spectra of simulated galaxies from two simulation suites in order to study to what extent these can accurately reproduce the spectral features (specifically the Balmer break) observed in MACS1149-JD1. We show that while the simulations used in this study produce galaxies with varying star formation histories, galaxies such as MACS1149-JD1 would be very rare in the simulations. In principle, future observations with the James Webb Space Telescope may tell us if MACS1149-JD1 represents something rare, or if such galaxies are more common than predicted by current simulations.

Kinematic asymmetry of galaxy pairs

2019 ◽  
Vol 14 (S353) ◽  
pp. 262-263
Author(s):  
Shuai Feng ◽  
Shi-Yin Shen ◽  
Fang-Ting Yuan
Keyword(s):  
Star Formation ◽  
Velocity Field ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Control Sample ◽  
Interacting Galaxies ◽  
Ionized Gas ◽  
Galaxy Interaction ◽  
The Galaxy

AbstractThe interaction between galaxies is believed to be the main origin of the peculiarities of galaxies. It can disturb not only the morphology but also the kinematics of galaxies. These disturbed and asymmetric features are the indicators of galaxy interaction. We study the velocity field of ionized gas in galaxy pairs based on MaNGA survey. Using the kinemetry package, we fit the velocity field and quantify the degree of kinematic asymmetry. We find that the fraction of high kinematic asymmetry is much higher for galaxy pairs with dp⩽30h−1kpc. Moreover, compared to a control sample of single galaxies, we find that the star formation rate is enhanced in paired galaxies with high kinematic asymmetry. For paired galaxies with low kinematic asymmetry, no significant SFR enhancement has been found. The galaxy pairs with high kinematic asymmetry are more likely to be real interacting galaxies rather than projected pairs.

scholarly journals Infrared Emission from Barred Spiral Galaxies

1996 ◽  
Vol 157 ◽  
pp. 54-62
Author(s):  
Tim G. Hawarden ◽  
J. H. Huang ◽  
Q. S. Gu
Keyword(s):  
Star Formation ◽  
Spiral Galaxies ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Infrared Emission ◽  
Stellar Radiation ◽  
The Galaxy ◽  
Barred Spiral Galaxies ◽  
Star Formation Regions ◽  
Ir Emission

AbstractAmongst relatively undisturbed spiral galaxies of type ≤ Sc barred morphology is unquestionably associated with powerful mid- and Far-IR emission. On the other hand, even amongst early type galaxies, those with LFIR/LB < 1/3 exhibit no association of high relative FIR luminosity with barred morphology, but some association of IR colors resembling those of star formation regions (SFRs). Amongst systems with LFIR/LB < 0.1 this ratio may be anti-correlated with barredness. It appears that enhanced IR emission from those galaxies whose star formation rate is currently elevated by the the bar translates them into the group with higher FIR-to-optical luminosity ratios. Depletion of extended nearnuclear gas and dust, once the bar has swept up the currently-available supplies, may reduce the fraction of the background stellar radiation field which can be converted to FIR radiation in the inner, most luminous parts of the galaxy. Thus, after the starburst has subsided, such galaxies may be less FIR-luminous than unbarred systems. Several uncertainties remain: it is still not clear whether barred morphology is a necessary condition for the generation of a starburst in an otherwise undisturbed galaxy, while evidence as to the effect of differing bar strengths is conflicting.

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 &lt; 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.

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