Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userFar-infrared Herschel SPIRE spectroscopy of lensed starbursts reveals physical conditions of ionised gas
109
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
The most intensively star-forming galaxies are extremely luminous at far-infrared (FIR) wavelengths, highly obscured at optical and ultraviolet wavelengths, and lie at $zge 1-3$. We present a programme of ${it Herschel}$ FIR spectroscopic observations with the SPIRE FTS and photometric observations with PACS, both on board ${it Herschel}$, towards a sample of 45 gravitationally lensed, dusty starbursts across $zsim 1-3.6$. In total, we detected 27 individual lines down to 3-$sigma$, including nine $[rm C{small II}]$ 158-$mu$m lines with confirmed spectroscopic redshifts, five possible $[rm C{small II}]$ lines consistent with their far-infrared photometric redshifts, and in some individual sources a few $[rm O{small III}]$ 88-$mu$m, $[rm O{small III}]$ 52-$mu$m, $[rm O{small I}]$ 145-$mu$m, $[rm O{small I}]$ 63-$mu$m, $[rm N{small II}]$ 122-$mu$m, and OH 119-$mu$m (in absorption) lines. To derive the typical physical properties of the gas in the sample, we stack all spectra weighted by their intrinsic luminosity and by their 500-$mu$m flux densities, with the spectra scaled to a common redshift. In the stacked spectra, we detect emission lines of $[rm C{small II}]$ 158-$mu$m, $[rm N{small II}]$ 122-$mu$m, $[rm O{small III}]$ 88-$mu$m, $[rm O{small III}]$ 52-$mu$m, $[rm O{small I}]$ 63-$mu$m, and the absorption doublet of OH at 119-$mu$m, at high fidelity. We find that the average electron densities traced by the $[rm N{small II}]$ and $[rm O{small III}]$ lines are higher than the average values in local star-forming galaxies and ULIRGs, using the same tracers. From the $[rm N{small II}]/[rm C{small II}]$ and $[rm O{small I}]/[rm C{small II}]$ ratios, we find that the $[rm C{small II}]$ emission is likely dominated by the photo-dominated regions (PDR), instead of by ionised gas or large-scale shocks.
rate research
Read More
We present spectroscopic observations for a sample of 36 Herschel-SPIRE 250-500um selected galaxies (HSGs) at 2<z<5 from the Herschel Multi-tiered Extragalactic Survey (HerMES). Redshifts are confirmed as part of a large redshift survey of Herschel-SPIRE-selected sources covering ~0.93deg^2 in six extragalactic legacy fields. Observations were taken with the Keck I Low Resolution Imaging Spectrometer (LRIS) and the Keck II DEep Imaging Multi-Object Spectrograph (DEIMOS). Precise astrometry, needed for spectroscopic follow-up, is determined by identification of counterparts at 24um or 1.4GHz using a cross-identification likelihood matching method. Individual source luminosities range from log(L_IR/Lsun)=12.5-13.6 (corresponding to star formation rates 500-9000Msun/yr, assuming a Salpeter IMF), constituting some of the most intrinsically luminous, distant infrared galaxies yet discovered. We present both individual and composite rest-frame ultraviolet spectra and infrared spectral energy distributions (SEDs). The selection of these HSGs is reproducible and well characterized across large areas of sky in contrast to most z>2 HyLIRGs in the literature which are detected serendipitously or via tailored surveys searching only for high-z HyLIRGs; therefore, we can place lower limits on the contribution of HSGs to the cosmic star formation rate density at (7+-2)x10^(-3)Msun/yr h^3Mpc^(-3) at z~2.5, which is >10% of the estimated total star formation rate density (SFRD) of the Universe from optical surveys. The contribution at z~4 has a lower limit of 3x10^(-3)Msun/yr h^3 Mpc^(-3), ~>20% of the estimated total SFRD. This highlights the importance of extremely infrared-luminous galaxies with high star formation rates to the build-up of stellar mass, even at the earliest epochs.
We report the redshift of HATLAS J132427.0+284452 (hereafter HATLAS J132427), a gravitationally lensed starburst galaxy, the first determined blind by the Herschel Space Observatory. This is achieved via the detection of [C II] consistent with z = 1.68 in a far-infrared spectrum taken with the SPIRE Fourier Transform Spectrometer. We demonstrate that the [C II] redshift is secure via detections of CO J = 2 - 1 and 3 - 2 using the Combined Array for Research in Millimeter-wave Astronomy and the Institut de Radioastronomie Millimetriques Plateau de Bure Interferometer. The intrinsic properties appear typical of high-redshift starbursts despite the high lensing-amplified fluxes, proving the ability of the FTS to probe this population with the aid of lensing. The blind detection of [C II] demonstrates the potential of the SAFARI imaging spectrometer, proposed for the much more sensitive SPICA mission, to determine redshifts of multiple dusty galaxies simultaneously without the benefit of lensing.
In this work, we investigate the strength and impact of ionised gas outflows within $z sim 0.04$ MaNGA galaxies. We find evidence for outflows in 322 galaxies ($12%$ of the analysed line-emitting sample), 185 of which show evidence for AGN activity. Most outflows are centrally concentrated with a spatial extent that scales sublinearly with $R_{rm e}$. The incidence of outflows is enhanced at higher masses, central surface densities and deeper gravitational potentials, as well as at higher SFR and AGN luminosity. We quantify strong correlations between mass outflow rates and the mechanical drivers of the outflow of the form $dot{M}_{rm out} propto rm SFR^{0.97}$ and $dot{M}_{rm out} propto L_{rm AGN}^{0.55}$. We derive a master scaling relation describing the mass outflow rate of ionised gas as a function of $M_{star}$, SFR, $R_{rm e}$ and $L_{rm AGN}$. Most of the observed winds are anticipated to act as galactic fountains, with the fraction of galaxies with escaping winds increasing with decreasing potential well depth. We further investigate the physical properties of the outflowing gas finding evidence for enhanced attenuation in the outflow, possibly due to metal-enriched winds, and higher excitation compared to the gas in the galactic disk. Given that the majority of previous studies have focused on more extreme systems with higher SFRs and/or more luminous AGN, our study provides a unique view of the non-gravitational gaseous motions within `typical galaxies in the low-redshift Universe, where low-luminosity AGN and star formation contribute jointly to the observed outflow phenomenology.
Herbig Ae/Be objects, like their lower mass counterparts T Tauri stars, are seen to form a stable circumstellar disk which is initially gas-rich and could ultimately form a planetary system. We present Herschel SPIRE 460-1540 GHz spectra of five targets out of a sample of 13 young disk sources, showing line detections mainly due to warm CO gas.
We employ MUSE/VLT data to study the ionised and highly ionised gas phases of the feedback in Circinus, the closest Seyfert 2 galaxy to us. The analysis of the nebular emission allowed us to detect a remarkable high-ionisation gas outflow beyond the galaxy plane traced by the coronal lines [Fe VII] $lambda$6089 and [Fe X] $lambda$6374, extending up to 700 pc and 350 pc NW from the nucleus, respectively. This is the first time that the [Fe X] emission is observed at such distances from the central engine in an AGN. The gas kinematics reveals expanding gas shells with velocities of a few hundred km s$^{-1}$, spatially coincident with prominent hard X-ray emission detected by Chandra. Density and temperature sensitive line ratios show that the extended high-ionisation gas is characterized by a temperature reaching 25000 K and an electron density > 10$^2$ cm$^{-3}$. We found that local gas excitation by shocks produced by the passage of a radio jet leads to the spectacular high-ionisation emission in this object. This hypothesis is fully supported by photoionisation models that accounts for the combined effects of the central engine and shocks. They reproduce the observed emission line spectrum at different locations inside and outside of the NW ionisation cone. The energetic outflow produced by the radio jet is spatially located close to an extended molecular outflow recently reported using ALMA which suggests that they both represent different phases of the same feedback process acting on the AGN.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
