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

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.

Download Full-text

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

BIBECHANA ◽

10.3126/bibechana.v18i1.29466 ◽

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

Download Full-text

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

Journal of Nepal Physical Society ◽

10.3126/jnphyssoc.v7i2.38622 ◽

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.

Download Full-text

A cautionary tale of attenuation in star-forming regions

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa919 ◽

2020 ◽

Vol 494 (4) ◽

pp. 4751-4770 ◽

Cited By ~ 2

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.

Download Full-text

Detection of a high-redshift molecular outflow in a primeval hyperstarburst galaxy

Astronomy and Astrophysics ◽

10.1051/0004-6361/201936989 ◽

2019 ◽

Vol 632 ◽

pp. L7 ◽

Cited By ~ 3

Author(s):

G. C. Jones ◽

R. Maiolino ◽

P. Caselli ◽

S. Carniani

Keyword(s):

Star Formation ◽

High Redshift ◽

Formation Rate ◽

Host Galaxy ◽

Starburst Galaxy ◽

High Excitation ◽

Star Formation Region ◽

Molecular Outflow ◽

Outflow Rate ◽

Major Merger

We report the discovery of a high-redshift, massive molecular outflow in the starburst galaxy SPT 0346-52 (z = 5.656) via the detected absorption of high-excitation water transitions (H2O 42,3 − 41,4 and H2O 33,0 − 32,1) with the Atacama Large Millimeter/submillimeter Array (ALMA). The host galaxy is one of the most powerful starburst galaxies at high redshift (star formation rate; SFR ∼3600 M⊙ year−1), with an extremely compact (∼320 pc) star formation region and a SFR surface density (ΣSFR ∼ 5500 M⊙ year−1 kpc−2) five times higher than “maximum” (i.e. Eddington-limited) starbursts, implying a highly transient phase. The estimated outflow rate is ∼500 M⊙ year−1, which is much lower than the SFR, implying that in this extreme starburst the outflow capabilities saturate and the outflow is no longer capable of regulating star formation, resulting in a runaway process in which star formation will use up all available gas in less than 30 Myr. Finally, while previous kinematic investigations of this source revealed possible evidence for an ongoing major merger, the coincidence of the hyper-compact starburst and high-excitation water absorption indicates that this is a single starburst galaxy surrounded by a disc.

Download Full-text

Extended X-ray emission in PKS 1718−649

Astronomy and Astrophysics ◽

10.1051/0004-6361/201833064 ◽

2018 ◽

Vol 612 ◽

pp. L4 ◽

Cited By ~ 5

Author(s):

T. Beuchert ◽

A. Rodríguez-Ardila ◽

V. A. Moss ◽

R. Schulz ◽

M. Kadler ◽

...

Keyword(s):

Large Scale ◽

Star Formation Rate ◽

Formation Rate ◽

Effective Area ◽

Radio Spectrum ◽

Host Galaxy ◽

X Rays ◽

Radio Structure ◽

X Ray ◽

Close Proximity

PKS 1718−649 is one of the closest and most comprehensively studied candidates of a young active galactic nucleus (AGN) that is still embedded in its optical host galaxy. The compact radio structure, with a maximal extent of a few parsecs, makes it a member of the group of compact symmetric objects (CSO). Its environment imposes a turnover of the radio synchrotron spectrum towards lower frequencies, also classifying PKS 1718−649 as gigahertz-peaked radio spectrum (GPS) source. Its close proximity has allowed the first detection of extended X-ray emission in a GPS/CSO source with Chandra that is for the most part unrelated to nuclear feedback. However, not much is known about the nature of this emission. By co-adding all archival Chandra data and complementing these datasets with the large effective area of XMM-Newton, we are able to study the detailed physics of the environment of PKS 1718−649. Not only can we confirm that the bulk of the ≲kiloparsec-scale environment emits in the soft X-rays, but we also identify the emitting gas to form a hot, collisionally ionized medium. While the feedback of the central AGN still seems to be constrained to the inner few parsecs, we argue that supernovae are capable of producing the observed large-scale X-ray emission at a rate inferred from its estimated star formation rate.

Download Full-text

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

Astronomy and Astrophysics ◽

10.1051/0004-6361/201935495 ◽

2019 ◽

Vol 631 ◽

pp. A19 ◽

Cited By ~ 11

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.

Download Full-text

THE STAR FORMATION RATE AND METALLICITY OF THE HOST GALAXY OF THE DARK GRB 080325 ATz= 1.78

The Astrophysical Journal ◽

10.1088/0004-637x/806/2/250 ◽

2015 ◽

Vol 806 (2) ◽

pp. 250 ◽

Cited By ~ 13

Author(s):

Tetsuya Hashimoto ◽

Daniel A. Perley ◽

Kouji Ohta ◽

Kentaro Aoki ◽

Ichi Tanaka ◽

...

Keyword(s):

Star Formation ◽

Star Formation Rate ◽

Formation Rate ◽

Host Galaxy

Download Full-text

Stellar Explosions in High-surface Density Galaxies

Proceedings of the International Astronomical Union ◽

10.1017/s174392131600507x ◽

2015 ◽

Vol 11 (A29B) ◽

pp. 232-232

Author(s):

Evan Scannapieco ◽

Sharanya Sur ◽

Eve C. Ostriker

Keyword(s):

Star Formation ◽

Surface Density ◽

Energy Input ◽

Large Scale ◽

Star Formation Rate ◽

High Surface ◽

Formation Rate ◽

Three Dimensional ◽

Velocity Dispersions ◽

The Impact

AbstractHigh surface density, rapidly star-forming galaxies are observed to have ≈ 50 - 100 km s−1 line-of-sight velocity dispersions, which are much higher than expected from supernova driving alone, but may arise from large-scale gravitational instabilities. Using three-dimensional simulations of local regions of the interstellar medium, we explore the impact of high velocity dispersions that arise from these disk instabilities. Parametrizing disks by their surface densities and epicyclic frequencies, we conduct a series of simulations that probe a broad range of conditions. Turbulence is driven purely horizontally and on large scales, neglecting any energy input from supernovae.We find that such motions lead to strong global outflows in the highly-compact disks that were common at high redshifts, but weak or negligible mass loss in the more diffuse disks that are prevalent today. Substantial outflows are generated if the one-dimensional horizontal velocity dispersion exceeds -35 km s−1, as occurs in the dense disks that have star formation rate densities above ≈ 0.1 M⊙ yr−1 kpc−2. These outflows are triggered by a thermal runaway, arising from the inefficient cooling of hot material coupled with successive heating from turbulent driving. Thus, even in the absence of stellar feedback, a critical value of the star-formation rate density for outflow generation can arise due to a turbulent heating instability. This suggests that in strongly self-gravitating disks, outflows may be enhanced by, but need not caused by, energy input from stellar explosions.These results are explained in more detailed in Sur, Scannapieco, & Ostriker (2015).

Download Full-text