- ID:
- ivo://CDS.VizieR/J/A+A/595/A80
- Title:
- H_2_O lines reduced spectra in 11 ULIRGs or HyLIRGs
- Short Name:
- J/A+A/595/A80
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report rest-frame submillimeter H_2_O emission line observations of 11 ultra- or hyper-luminous infrared galaxies (ULIRGs or HyLIRGs) at z~2-4 selected among the brightest lensed galaxies discovered in the Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS). Using the IRAM NOrthern Extended Millimeter Array (NOEMA), we have detected 14 new H_2_O emission lines. These include five 3_21_-3_12_ ortho-H_2_O lines (Eup/k=305K) and nine J=2 para-H_2_O lines, either 2_02_-1_11_ (E_up/k=101K) or 2_11_-2_02_ (E_up/k = 137K). The apparent luminosities of the H_2_O emission lines are {mu}L_H2O_~6-21x10^8^L_{sun}_ (3<{mu}<15, where {mu} is the lens magnification factor), with velocity-integrated line fluxes ranging from 4-15Jy.km/s. We have also observed CO emission lines using EMIR on the IRAM 30m telescope in seven sources (most of those have not yet had their CO emission lines observed). The velocity widths for CO and H_2_O lines are found to be similar, generally within 1{sigma} errors in the same source. With almost comparable integrated flux densities to those of the high-J CO line (ratios range from 0.4 to 1.1), H_2_O is found to be among the strongest molecular emitters in high-redshift Hy/ULIRGs. We also confirm our previously found correlation between luminosity of H_2_O (LH_2_O) and infrared (LIR) that LH_2_O~LIR^(1.1-1.2)^, with our new detections. This correlation could be explained by a dominant role of far-infrared pumping in the H_2_O excitation. Modelling reveals that the far-infrared radiation fields have warm dust temperature T_warm_~45-75K, H_2_O column density per unit velocity interval N_H2O_/{DELTA}V>~0.3x10^15^km/s/cm^2^ and 100{mu}m continuum opacity {tau}_100_>1 (optically thick), indicating that H_2_O is likely to trace highly obscured warm dense gas. However, further observations of J>=4 H_2_O lines are needed to better constrain the continuum optical depth and other physical conditions of the molecular gas and dust. We have also detected H_2_O^+^ emission in three sources. A tight correlation between L_H_2_O and L_H_2_O^+^ has been found in galaxies from low to high redshift. The velocity-integrated flux density ratio between H_2_O^+^ and H_2_O suggests that cosmic rays generated by strong star formation are possibly driving the H_2_O^+^ formation.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/764/34
- Title:
- HRDS IV. H, He and C radio recombination lines
- Short Name:
- J/ApJ/764/34
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Green Bank Telescope H II Region Discovery Survey (GBT HRDS) found hundreds of previously unknown Galactic regions of massive star formation by detecting hydrogen radio recombination line (RRL) emission from candidate H II region targets. Since the HRDS nebulae lie at large distances from the Sun, they are located in previously unprobed zones of the Galactic disk. Here, we derive the properties of helium and carbon RRL emission from HRDS nebulae. Our target sample is the subset of the HRDS that has visible helium or carbon RRLs. This criterion gives a total of 84 velocity components (14% of the HRDS) with helium emission and 52 (9%) with carbon emission. For our highest quality sources, the average ^4^He^+^/H^+^ abundance ratio by number, <y^+^>, is 0.068+/-0.023(1{sigma}). This is the same ratio as that measured for the sample of previously known Galactic H II regions. Nebulae without detected helium emission give robust y^+^ upper limits. There are 5 RRL emission components with y^+^ less than 0.04 and another 12 with upper limits below this value. These H II regions must have either a very low ^4^He abundance or contain a significant amount of neutral helium. The HRDS has 20 nebulae with carbon RRL emission but no helium emission at its sensitivity level. There is no correlation between the carbon RRL parameters and the 8um mid-infrared morphology of these nebulae.
- ID:
- ivo://CDS.VizieR/J/ApJ/886/99
- Title:
- HST obs. in the region of 3 young LMC SNIa remnants
- Short Name:
- J/ApJ/886/99
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used two methods to search for surviving companions of Type Ia supernova progenitors in three Balmer-dominated supernova remnants in the Large Magellanic Cloud: 0519-69.0, 0505-67.9 (DEM L71), and 0548-70.4. In the first method, we use the Hubble Space Telescope photometric measurements of stars to construct color-magnitude diagrams (CMDs) and compare positions of stars in the CMDs with those expected from theoretical post-impact evolution of surviving main-sequence or helium star companions. No obvious candidates of surviving companions are identified in this photometric search. Future models for surviving red giant companions or with different explosion mechanisms are needed for thorough comparisons with these observations in order to make more definitive conclusions. In the second method, we use Multi Unit Spectroscopic Explorer observations of 0519-69.0 and DEM L71 to carry out spectroscopic analyses of stars in order to use large peculiar radial velocities as diagnostics of surviving companions. We find a star in 0519-69.0 and a star in DEM L71 moving at radial velocities of 182+/-0km/s and 213+/-0km/s, respectively, more than 2.5{sigma} from the mean radial velocity of the underlying stellar population, 264 and 270km/s, respectively. These stars need higher-quality spectra to investigate their abundances and rotation velocities to determine whether they are indeed surviving companions of the supernova progenitors.
- ID:
- ivo://CDS.VizieR/J/A+A/642/A87
- Title:
- Hub-filament candidates
- Short Name:
- J/A+A/642/A87
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Star formation takes place in giant molecular clouds, resulting in mass-segregated young stellar clusters composed of Sun-like stars, brown dwarves and massive O-type (50-100M_{sun}_) stars. To identify candidate hub-filament systems (HFS) in the Milky-Way and examine their role in the formation of the highest mass stars and star clusters. Filaments around ~35000 HiGAL clumps that are detected using the DisPerSE algorithm. Hub is defined as a junction of three or more filaments. Column density maps were masked by the filament skeletons and averaged for HFS and non-HFS samples to compute the radial profile along the filaments into the clumps. ~3700~(11%) are candidate HFS of which, ~2150~(60%) are pre-stellar, ~1400~(40%) are proto-stellar. All clumps with L>10^4^L_{sun}_ and L>10^5^L_{sun}_ at distances respectively within 2kpc and 5kpc are located in the hubs of HFS. The column-densities of hubs are found to be enhanced by a factor of ~2 (pre-stellar sources) up to ~10 (proto-stellar sources). All high-mass stars preferentially form in the density enhanced hubs of HFS. This amplification can drive the observed longitudinal flows along filaments providing further mass accretion. Radiation pressure and feedback can escape into the inter-filamentary voids. We propose a 'filaments to clusters' unified paradigm for star formation, with the following salient features: a) low-intermediate mass stars form in the filaments slowly (10^6^yr) and massive stars quickly (10^5^yr) in the hub, b) the initial mass function is the sum of stars continuously created in the HFS with all massive stars formed in the hub, c) Feedback dissipation and mass segregation arise naturally due to HFS properties, and c) explain age spreads within bound clusters and formation of isolated OB associations.
- ID:
- ivo://CDS.VizieR/J/A+A/600/A2
- Title:
- Hydrogen in diffuse molecular clouds
- Short Name:
- J/A+A/600/A2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recent sub-millimeter and far-infrared wavelength observations of absorption in the rotational ground state lines of various simple molecules against distant Galactic continuum sources have opened the possibility to study the chemistry of diffuse molecular clouds Milky Way-wide. In order to calculate abundances the column densities of molecular and atomic hydrogen, HI, must be known. We aim at determining the atomic hydrogen column densities for diffuse clouds located on the sight lines toward a sample of prominent high mass star forming regions that were intensely studied with the HIFI instrument onboard Herschel. Based on Jansky Very Large Array data, we employ the 21-cm HI absorption-line technique to construct profiles of the HI opacity versus radial velocity toward our target sources. These profiles are combined with lower resolution archival data of extended HI emission to calculate the HI column densities of the individual clouds along the sight lines. We employ Bayesian inference to estimate the uncertainties of the derived quantities. Our study delivers reliable estimates of the atomic hydrogen column density for a large number of diffuse molecular clouds at various Galactocentric distances. Together with column densities of molecular hydrogen derived from its surrogates observed with HIFI, the measurements can be used to characterize the clouds and, e.g., investigate the dependence of their chemistry on the molecular fraction.
- ID:
- ivo://CDS.VizieR/J/A+A/645/A110
- Title:
- Hypercompact HII regions
- Short Name:
- J/A+A/645/A110
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The derived physical parameters for young HII regions are normally determined assuming the emission region to be optically-thin. However, this is unlikely to hold for young HII regions such as Hyper-compact HII(HCHII) and Ultra-compact HII(UCHII) regions and leads to the underestimation of their properties. This can be overcome by fitting the SEDs over a wide range of radio frequencies. Two primary goals are (1) determining physical properties from radio SEDs and finding potential HCHII regions; (2) using these physical properties to investigate their evolution. We used Karl G. Jansky Very Large Array (VLA) to make observations of X-band and K-band with angular-resolutions of ~1.7" and ~0.7", respectively, toward 114 HII regions with rising-spectra between 1-5GHz. We complement our observations with VLA archival data and construct SEDs between 1-26GHz and model them assuming an ionisation-bounded HII region with uniform density. The sample has a mean electron density of ne=1.6*10^4^cm^-3^, diameter diam=0.14pc, and emission measure EM=1.9*10^7^pc/cm^6^. We identify 16 HCHII region candidates and 8 intermediate objects between the classes of HCHII and UCHII regions. The ne, diam, and EM change as expected, however, the Lyman continuum flux is relatively constant over time. We find that about 67% of Lyman continuum photons are absorbed by dust within these HII regions and the dust absorption fraction tends to be more significant for more compact and younger HII regions. Young HII regions are commonly located in dusty clumps; HCHII regions and intermediate objects are often associated with various masers, outflows, broad radio recombination lines, and extended green objects, and the accretion at the two stages tends to be quickly reduced or halted.
317. IC 3476 Halpha image
- ID:
- ivo://CDS.VizieR/J/A+A/646/A139
- Title:
- IC 3476 Halpha image
- Short Name:
- J/A+A/646/A139
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the IB(s)m galaxy IC 3476 observed in the context of the Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE), a blind narrow-band H{alpha}+[NII] imaging survey of the Virgo cluster carried out with MegaCam at the CFHT. The deep narrow-band image reveals a very pertubed ionised gas distribution that is characterised by a prominent banana-shaped structure in the front of the galaxy formed of giant HII regions crossing the stellar disc. Star-forming structures, at ~8kpc from the edges of the stellar disc, are also detected in a deep far-ultraviolet ASTROSAT/UVIT image. This particular morphology indicates that the galaxy is undergoing an almost edge-on ram pressure stripping event. The same H{alpha}+[NII] image also shows that the star formation activity is totally quenched in the leading edge of the disc, where the gas has been removed during the interaction with the surrounding medium. The spectral energy distribution fitting analysis of the multi-frequency data indicates that this quenching episode is very recent (~50Myr), and roughly corresponds to an increase of the star formation activity by a factor of ~161% in the inner regions with respect to that expected for secular evolution. The analysis of these data, whose angular resolution enables the study of the induced effects of the perturbation down to the scale of individual HII regions (r_eq_~=40pc), also suggests that the increase of star formation activity is due to the compression of the gas along the stellar disc of the galaxy, which is able to increase its mean electron density and boost the star formation process producing bright HII regions with luminosities up to L(H{alpha})~=10^38^erg/s. The combined analysis of the VESTIGE data with deep IFU spectroscopy gathered with MUSE and with high spectral resolution Fabry Perot data also indicates that the hydrodynamic interaction has deeply perturbed the velocity field of the ionised gas component while leaving that of the stellar disc unaffected. The comparison of the data with tuned high-resolution hydrodynamic simulations accounting for the different gas phases (atomic, molecular, ionised) consistently indicates that the perturbing event is very recent (50-150Myr), once again confirming that ram pressure stripping is a violent phenomenon that is able to perturb the evolution of galaxies in rich environments on short timescales.
- ID:
- ivo://CDS.VizieR/J/ApJ/743/131
- Title:
- Infrared absorbance of water H_2_O/H_2_O_2_ ice
- Short Name:
- J/ApJ/743/131
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recent surface chemistry experiments have shown that the hydrogenation of molecular oxygen on interstellar dust grains is a plausible formation mechanism, via hydrogen peroxide (H_2_O_2_), for the production of water (H_2_O) ice mantles in the dense interstellar medium. Theoretical chemistry models also predict the formation of a significant abundance of H_2_O_2_ ice in grain mantles by this route. At their upper limits, the predicted and experimental abundances are sufficiently high that H_2_O_2_ should be detectable in molecular cloud ice spectra. To investigate this further, laboratory spectra have been obtained for H_2_O_2_/H_2_O ice films between 2.5 and 200um, from 10 to 180K, containing 3%, 30%, and 97% H_2_O_2_ ice. Integrated absorbances for all the absorption features in low-temperature H_2_O_2_ ice have been derived from these spectra. For identifying H_2_O_2_ ice, the key results are the presence of unique features near 3.5, 7.0, and 11.3um. Comparing the laboratory spectra with the spectra of a group of 24 protostars and field stars, all of which have strong H_2_O ice absorption bands, no absorption features are found that can definitely be identified with H_2_O_2_ ice. In the absence of definite H_2_O_2_ features, the H_2_O_2_ abundance is constrained by its possible contribution to the weak absorption feature near 3.47um found on the long-wavelength wing of the 3um H_2_O ice band. This gives an average upper limit for H_2_O_2_, as a percentage of H_2_O, of 9%+/-4%. This is a strong constraint on parameters for surface chemistry experiments and dense cloud chemistry models.
- ID:
- ivo://CDS.VizieR/J/A+A/419/999
- Title:
- Infrared knots along protostellar jets
- Short Name:
- J/A+A/419/999
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the near infrared spectra (0.9-2.5 micron) of protostellar jets (HH 24-26, HH72, BHR71). The observations were carried out with Sofi at R~600 with the 1x290arcsec slit. The spectra are dominated by H2 rovibrational lines (v up 5). Faint emission from ionized material in form of [FeII] and [SII] lines is also recognizable. The tables contain the observed lines together with the measured flux. The reported error derives from the rms of the baseline, multiplied by the width of the instrumental profile (30 Angstrom).
- ID:
- ivo://CDS.VizieR/J/A+A/532/A127
- Title:
- Inner Galaxy HII regions
- Short Name:
- J/A+A/532/A127
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report simultaneous H110{alpha} and H_2_CO line observations with the 25m radio telescope of Nanshan station toward 251 HII regions. We used the H110{alpha} line to establish the velocity of the HII regions and H_2_CO absorption lines to distinguish between near and far distances. We detected the H110{alpha} RRLs in 28 sources and H_2_CO absorption lines in 59 sources. In the latter case, 43 features had not previously been observed. H_2_CO and H110{alpha} lines were simultaneously detected toward 23 HII regions. We resolved the kinematic distance ambiguities for 14 HII regions and 20 intervening molecular clouds.
