Search

Gaseous flows inside and outside galaxies are key to understanding galaxy evolution, as they regulate their star formation activity and chemical enrichment across cosmic time. We study the interstellar medium (ISM) kinematics of a sample of 330 galaxies with C III] or He II emission using far-ultraviolet (far-UV) ISM absorption lines detected in the ultra deep spectra of the VANDELS survey. These galaxies span a broad range of stellar masses from 10(8) to 10(11) M-circle dot, and star formation rates (SFRs) from 1 to 500 M-circle dot yr(-1) in the redshift range between 2 and 5. We find that the bulk ISM velocity along the line of sight (v(IS)) is globally in outflow, with a v(IS) of -60 +/- 10 km s(-1) for low-ionisation gas traced by Si II lambda 1260 angstrom, C II lambda 1334 angstrom, Si II lambda 1526 angstrom, and Al II lambda 1670 angstrom absorption lines, and a v(IS) of -160 +/- 30 and -170 +/- 30 km s(-1) for higher ionisation gas traced respectively by Al III lambda lambda 1854-1862 angstrom and Si IV lambda lambda 1393-1402 angstrom. Interestingly, we notice that BPASS models are able to better reproduce the stellar continuum around the Si IV doublet than other stellar population templates. For individual galaxies, 34% of the sample has a positive ISM velocity shift, almost double the fraction reported at lower redshifts. We additionally derive a maximum outflow velocity v(max) for the average population, which is of the order of similar to -500 and similar to -600 km s(-1) for the lower and higher ionisation lines, respectively. Comparing v(IS) to the host galaxies properties, we find no significant correlations with stellar mass M-star or SFR, and only a marginally significant dependence (at similar to 2 sigma) on morphology-related parameters, with slightly higher velocities found in galaxies of smaller size (probed by the equivalent radius r(T)(50)) higher concentration (C-T), and higher SFR surface density Sigma(SFR). From the spectral stacks, v(max) shows a similarly weak dependence on physical properties (at similar or equal to 2 sigma). Moreover, we do not find evidence of enhanced outflow velocities in visually identified mergers compared to isolated galaxies. From a physical point of view, the outflow properties are consistent with accelerating momentum-driven winds, with densities decreasing towards the outskirts. Our moderately lower ISM velocities compared to those found in similar studies at lower redshifts suggest that inflows and internal turbulence might play an increased role at z > 2 and weaken the outflow signatures. Finally, we estimate mass-outflow rates (M) over dot(out) that are comparable to the SFRs of the galaxies (hence a mass-loading factor eta of the order of unity), and an average escape velocity of 625 km s(-1), suggesting that most of the ISM will remain bound to the galaxy halo.

Recent work has shown that UV-luminous reionization-era galaxies often exhibit strong Lyman-alpha emission despite being situated at redshifts where the IGM is thought to be substantially neutral. It has been argued that this enhanced Ly alpha transmission reflects the presence of massive galaxies in overdense regions which power large ionized bubbles. An alternative explanation is that massive galaxies shift more of their Ly alpha profile to large velocities (relative to the systemic redshift) where the IGM damping wing absorption is reduced. Such a mass-dependent trend is seen at lower redshifts, but whether one exists at z similar to 7 remains unclear owing to the small number of existing systemic redshift measurements in the reionization era. This is now changing with the emergence of [C ii]-based redshifts from ALMA. Here, we report MMT/Binospec Ly alpha spectroscopy of eight UV-bright (M-UV similar to -22) galaxies at z similar or equal to 7 selected from the ALMA REBELS survey. We detect Ly alpha in four of eight galaxies and use the [C ii] systemic redshifts to investigate the Ly alpha velocity profiles. The Ly alpha lines are significantly redshifted from systemic (average velocity offset = 223 km s(-1)) and broad (FWHM approximate to 300-650 km s(-1)), with two sources showing emission extending to approximate to 750 km s(-1). We find that the broadest Ly alpha profiles are associated with the largest [C ii] line widths, suggesting a potential link between the Ly alpha FWHM and the dynamical mass. Since Ly alpha photons at high velocities transmit efficiently through the z = 7 IGM, our data suggest that velocity profiles play a significant role in boosting the Ly alpha visibility of the most UV-luminous reionization-era galaxies.

We report the discovery of J0121+0025, an extremely luminous and young star-forming galaxy (M_UV = -24.11, log[L_Lya / erg s^-1] = 43.8) at z = 3.244 showing copious Lyman continuum (LyC) leakage (f_esc,abs ~ 40%). High signal-to-noise ratio rest-frame UV spectroscopy with the Gran Telescopio Canarias reveals a high significance (7.9 sigma) emission below the Lyman limit (< 912A), with a flux density level f_900A = 0.78 +/- 0.10 uJy, and strong P-Cygni in wind lines of OVI 1033A, NV 1240A and CIV 1550A that are indicative of a young age of the starburst (, 16 pages, 8 figures, 2 tables. Accepted for publication in MNRAS. v2: reference list updated

Star-forming galaxies are composed of various types of galaxies. However, the luminosity functions at z ≳ 4–5 suggest that most galaxies have a relatively low stellar mass (log Mstar ∼ 10) and a low dust attenuation (AFUV ∼ 1.0). The physical properties of these objects are quite homogeneous. We used an approach where we combined their rest-frame far-infrared and submillimeter emissions and utilized the universe and the redshift as a spectrograph to increase the amount of information in a collective way. From a subsample of 27 ALMA-detected galaxies at z > 4.5, we built an infrared spectral energy distribution composite template. It was used to fit, with CIGALE, the 105 galaxies (detections and upper limits) in the sample from the far-ultraviolet to the far-infrared. The derived physical parameters provide information to decipher the nature of the dust cycle and of the stellar populations in these galaxies. The derived IR composite template is consistent with the galaxies in the studied sample. A delayed star formation history with τmain = 500 Myr is slightly favored by the statistical analysis as compared to a delayed with a final burst or a continuous star formation history. The position of the sample in the star formation rate (SFR) versus Mstar diagram is consistent with previous papers. The redshift evolution of the log Mstar versus AFUV relation is in agreement with an evolution in redshift of this relation. This evolution is necessary to explain the cosmic evolution of the average dust attenuation of galaxies. Evolution is also observed in the Ldust/LFUV (IRX) versus UV slope βFUV diagram: younger galaxies have bluer βFUV. We modeled the shift of galaxies in the IRX versus the βFUV diagram with the mass-weighted age as a free parameter, and we provide an equation to make predictions. The large sample studied in this paper is generally consistent with models that assume rapid dust formation from supernovae and removal of dust by outflows and supernovae blasts. However, we find that high mass dusty star-forming galaxies cannot be explained by the models.

We use VANDELS spectroscopic data overlapping with the $\simeq$7 Ms Chandra Deep Field South survey to extend studies of high-mass X-ray binary systems (XRBs) in 301 normal star-forming galaxies in the redshift range $3 < z < 5.5$. Our analysis evaluates correlations between X-ray luminosities ($L_X$), star formation rates (SFR) and stellar metallicities ($Z_\star$) to higher redshifts and over a wider range in galaxy properties than hitherto. Using a stacking analysis performed in bins of both redshift and SFR for sources with robust spectroscopic redshifts without AGN signatures, we find convincing evolutionary trends in the ratio $L_X$/SFR to the highest redshifts probed, with a stronger trend for galaxies with lower SFRs. Combining our data with published samples at lower redshift, the evolution of $L_X$/SFR to $z\simeq5$ proceeds as $(1 + z)^{1.03 \pm 0.02}$. Using stellar metallicities derived from photospheric absorption features in our spectroscopic data, we confirm indications at lower redshifts that $L_X$/SFR is stronger for metal-poor galaxies. We use semi-analytic models to show that metallicity dependence of $L_X$/SFR alone may not be sufficient to fully explain the observed redshift evolution of X-ray emission from high-mass XRBs, particularly for galaxies with SFR $6$ may be $\gtrsim 0.25$ dex higher than previously estimated., 16 pages, 10 figures, Published in MNRAS

Downflows with high velocities occur in the transition region above many sunspots; however, how these signatures evolve over short time-scales in both spatial and spectral terms is still unknown. In this article, we investigate the evolution of downflows detected within the transition region on time-scales of the order minutes and search for clues as to their formation mechanisms in co-temporal imaging data. The high-resolution spectral and imaging data used to identify downflows here were sampled by IRIS on the 20th and 21st May 2015. Imaging data from the Hinode and SDO satellites provided context about the wider solar atmosphere. Four downflows were identified and analysed. The potential super-sonic components of these downflows had widths of around 2" and evolved over time-scales of the order minutes. The measured apparent downflow velocities were structured both in time and space, with the highest apparent velocities occurring above a bright region detected in Si IV 1400 {\AA} images. Downflows with apparent velocities below 50 km s^{-1} were observed to extend a few arcsecs away from the foot-points suggesting the potential super-sonic components are linked to larger-scale flows. The electron density and mass flux for these events were within the ranges 10^{9.6}-10^{10.2} cm^{-3} and 10^{-6.81}-10^{-7.48} g cm^{-2} s^{-1}, respectively. Each downflow formed at the foot-point of thin `fingers' extending out around 3-5" in Si IV 1400 {\AA} data with smaller widths (, Comment: 13 pages, 10 figures, accepted for publication in Astronomy and Astrophysics

The Lya line in the UV and the [CII] line in the FIR are widely used tools to identify galaxies and to obtain insights into ISM properties in the early Universe. By combining data obtained with ALMA in band 7 at ~ 320 GHz as part of the ALMA Large Program to INvestigate [CII] at Early Times (ALPINE) with spectroscopic data from DEIMOS at Keck, VIMOS and FORS2 at the VLT, we assembled a unique sample of 53 main-sequence star-forming galaxies at 4.4 < z < 6 in which we detect both the Lya line and the [CII]. We used [CII], observed with ALMA, as a tracer of the systemic velocity of the galaxies, and we find that 90% of the selected objects have Lya-[CII] velocity offsets in the range 0 < Dv_Lya-[CII] < 400 km/s, in line with the few measurements available so far in the early Universe, and significantly smaller than those observed at lower z. We observe ISM-[CII] offsets in the range -500 < Dv_ISM-[CII] < 0 km/s, in line with values at all redshifts. We find significant anticorrelations between Dv_Lya-[CII] and the Lya rest-frame equivalent width EW0(Lya) (or equivalently, the Lya escape fraction f_esc(Lya)). According to available models for the radiative transfer of Lya photons, the escape of Lya photons would be favored in galaxies with high outflow velocities, in agreement with our observations. The uniform shell model would also predict that the Lya escape in galaxies with slow outflows (0 < v_out < 300 km/s) is mainly determined by the neutral hydrogen column density (NHI), while the alternative model by Steidel+10 would favor a combination of NHI and covering fraction as driver of the Lya escape. We suggest that the observed increase in Lya escape that is observed between z~2 and z~6 is not due to a higher incidence of fast outflows at high redshift, but rather to a decrease in average NHI along the line of sight, or alternatively, a decrease in HI covering fraction. [abridged], Comment: 22 pages, 6 figures, accepted for publication in A&A. This version replaces the previous one

We present deep rest-frame UV spectroscopic observations using the Gran Telescopio Canarias of six gravitationally lensed Ly¿ emitters (LAEs) at 2.36 < z < 2.82 selected from the BELLS GALLERY survey. By taking the magnifications into account, we show that LAEs can be as luminous as LLy¿ ¿ 30 × 1042 erg s-1 and MUV ¿ -23 (AB) without invoking an AGN component, in contrast with previous findings. We measure Ly¿ rest-frame equivalent widths, EW0 (Ly¿), ranging from 16 to 50 Å and Ly¿ escape fractions, f_esc (Ly¿), from 10 per cent to 40 per cent. Large EW0 (Ly¿) and f_esc (Ly¿) are found predominantly in LAEs showing weak low-ionization ISM absorption (EW0 ¿ 1 Å) and narrow Ly¿ profiles (¿300 km s-1 FWHM) with their peak close (¿80 km s-1) to their systemic redshifts, suggestive of less scatter from low H I column densities that favours the escape of Ly¿ photons. We infer stellar metallicities of Z/Z¿ ¿ 0.2 in almost all LAEs by comparing the P-Cygni profiles of the wind lines N V1240 Å and C IV1549 Å with those from stellar synthesis models. We also find a trend between MUV and the velocity offset of ISM absorption lines, such as the most luminous LAEs experience stronger outflows. The most luminous LAEs show star formation rates up to ¿180 M¿ yr-1, yet they appear relatively blue (ßUV ¿ -1.8 to -2.0) showing evidence of little dust attenuation [E(B - V) = 0.10-0.14]. These luminous LAEs may be particular cases of young starburst galaxies that have had no time to form large amounts of dust. If so, they are ideal laboratories to study the early phase of massive star formation, stellar and dust mass growth, and chemical enrichment histories of starburst galaxies at high-z., With funding from the Spanish government through the "María de Maeztu Unit of Excellence" accreditation (MDM-2017-0737)

Identifying the mechanisms driving the escape of Lyman Continuum (LyC) photons is crucial to find Lyman Continuum Emitter (LCE) candidates. To understand the physical properties involved in the leakage of LyC photons, we investigate the connection between the HI covering fraction, HI velocity width, the Lyman alpha (LyA) properties and escape of LyC photons in a sample of 22 star-forming galaxies including 13 LCEs. We fit the stellar continua, dust attenuation, and absorption lines between 920 and 1300 A to extract the HI covering fractions and dust attenuation. Additionally, we measure the HI velocity widths of the optically thick Lyman series and derive the LyA equivalent widths (EW), escape fractions (fesc), peak velocities and fluxes at the minimum of the LyA profiles. Overall, we highlight strong correlations between the presence of low HI covering fractions and (1) low LyA peak velocities; (2) more flux at the profile minimum; and (3) larger EW(LyA), fesc(LyA), and fesc(LyC). Hence, low column density channels are crucial ISM ingredients for the leakage of LyC and LyA photons. Additionally, galaxies with narrower HI absorption velocity widths have higher LyA equivalent widths, larger LyA escape fractions, and lower LyA peak velocity separations. This suggests that these galaxies have low HI column density. Finally, we find that dust regulates the amount of LyA and LyC radiation that actually escapes the ISM. Overall, the ISM porosity is one origin of strong LyA emission and enables the escape of ionizing photons in low-z leakers. However, this is not enough to explain the largest fesc(LyC) observed, which indicates that the most extreme LCEs are likely density-bounded along all lines of sight to the observer. Overall, the neutral gas porosity constrains a lower limit to the escape fraction of LyC and LyA photons, providing a key estimator of the leakage of ionizing photons., Comment: Accepted for publication in A&A. 28 pages, 23 figures, 7 tables

We report a multi-wavelength study of the massive ($M_{\star} \gtrsim 10^{11} \rm{M}_{\odot}$), $z\sim 2$ star-forming galaxy GMASS 0953, which hosts an obscured AGN. We combined near-infrared observations of the GNIRS, SINFONI and KMOS spectrographs to study the kinematics of the [O III]$\lambda 5007$ and H$\alpha$ emission lines. Our analysis shows that GMASS 0953 may host an ionized disc extending up to 13 kpc, which rotates at a velocity of $V_{\rm{ion}} = 203^{+17}_{-20} {\ \rm kms}^{-1}$ at the outermost radius. Evidence of rotation on a smaller scale ($R \sim 1$ kpc) arises from the CO(J=6-5) line. The central velocity $V_{\rm{CO}} = 320^{+ 92}_{-53} {\ \rm kms}^{-1}$ traced by the molecular gas is higher than $V_{\rm{ion}}$, suggesting that the galaxy harbors a multi-phase disc with a rotation curve that peaks in the very central regions. The galaxy appears well located on the $z = 0$ baryonic Tully-Fisher relation. We also discuss the possibility that the [O III]$\lambda 5007$ and H$\alpha$ velocity gradients are due to a galactic-scale wind. Besides, we found evidence of an AGN-driven outflow traced by a broad blueshifted wing affecting the [O III]$\lambda 5007$ line, which presents a velocity offset $\Delta v = -535 \pm 152 {\ \rm kms}^{-1}$ from the systemic velocity. Because of the short depletion timescale ($\tau_{\rm{dep}}\sim 10^8$ yr) due to gas ejection and gas consumption by star formation activity, GMASS 0953 may likely evolve into a passive galaxy. However, the role of the AGN in depleting the gas reservoir of the galaxy is quite unclear because of the uncertainties affecting the outflow rate., Comment: 18 pages, 12 figures

We present an analysis of cool outflowing gas around galaxies, traced by Mg II absorption lines in the coadded spectra of a sample of 486 zCOSMOS galaxies at 1 ≤ z ≤ 1.5. These galaxies span a range of stellar masses (9.45 ≤ log10[M */M ☉] ≤ 10.7) and star formation rates (0.14 ≤ log10[SFR/M ☉ yr–1] ≤ 2.35). We identify the cool outflowing component in the Mg II absorption and find that the equivalent width of the outflowing component increases with stellar mass. The outflow equivalent width also increases steadily with the increasing star formation rate of the galaxies. At similar stellar masses, the blue galaxies exhibit a significantly higher outflow equivalent width as compared to red galaxies. The outflow equivalent width shows strong correlation with the star formation surface density (ΣSFR) of the sample. For the disk galaxies, the outflow equivalent width is higher for the face-on systems as compared to the edge-on ones, indicating that for the disk galaxies, the outflowing gas is primarily bipolar in geometry. Galaxies typically exhibit outflow velocities ranging from –150 km s–1 ~–200 km s–1 and, on average, the face-on galaxies exhibit higher outflow velocity as compared to the edge-on ones. Galaxies with irregular morphologies exhibit outflow equivalent width as well as outflow velocities comparable to face on disk galaxies. These galaxies exhibit mass outflow rates >5-7 M ☉ yr–1 and a mass loading factor () comparable to the star formation rates of the galaxies.

We present VLT/X-Shooter and MUSE spectroscopy of a faint F814W = 28.60 +/- 0.33 (M-UV = -17.0), low-mass (less than or similar to 10(7)M(circle dot)), and compact (R-eff = 62 pc) freshly star-forming galaxy at z = 3.1169 magnified (16x) by the Hubble Frontier Fields galaxy cluster Abell S1063. Gravitational lensing allows for a significant jump toward lowluminosity regimes, in moderately high-resolution spectroscopy (R = lambda/d lambda similar to 3000-7400). We measured C IV lambda 1548, 1550, He II lambda 1640, OIII] lambda 1661, 1666, CIII]lambda lambda 1907, 1909, H beta, [O III] lambda lambda 4959, 5007 emission lines with FWHM less than or similar to 50 km s(-1) and (de-lensed) fluxes spanning the interval 1.0 x 10(-19)-2 x 10(-18) erg s(-1) cm(-2) at signal-to-noise ratio (S/N) = 4-30. The double-peaked Ly alpha emission with Delta v(red -blue) = 280(+/- 7) km s(-1) and delensed fluxes 2.4((blue))vertical bar 8.5((red)) x 10(-18) erg s(-1) cm(-2) (S/N = 38((blue))vertical bar 110((red)) indicate a low column density of neutral hydrogen gas consistent with a highly ionized interstellar medium as also inferred from the large [O III]lambda 5007/[O II] lambda 3727 > 10 ratio. We detect C IV lambda 1548, 1550 resonant doublet in emission, each component with FWHM less than or similar to 45 km s(-1) and redshifted by + 51(+/- 10) km s(-1) relative to the systemic redshift. We interpret this as nebular emission tracing an expanding optically thin interstellar medium. Both C IV lambda 1548, 1550 and He II lambda 1640 suggest the presence of hot and massive stars (with a possible faint active galactic nucleus). The ultraviolet slope is remarkably blue, beta = -2.95 +/- 0.20 (F-lambda = lambda(beta)), consistent with a dust-free and young less than or similar to 20 Myr galaxy. Line ratios suggest an oxygen abundance 12 + log(O/H)

We present VLT/X-Shooter and MUSE spectroscopy of a faint F814W = 28.60 ± 0.33 ({M}{UV}=-17.0), low-mass (≲{10}7{M}☉ ), and compact (R eff = 62 pc) freshly star-forming galaxy at z = 3.1169 magnified (16×) by the Hubble Frontier Fields galaxy cluster Abell S1063. Gravitational lensing allows for a significant jump toward low-luminosity regimes, in moderately high-resolution spectroscopy (R=λ /dλ ∼ 3000{--}7400). We measured C IV λ 1548,1550, He II λ 1640, O III]λ 1661,1666, C III]λ λ 1907,1909, Hβ, [O III]λ λ 4959,5007 emission lines with {FWHM}≲ 50 km s-1 and (de-lensed) fluxes spanning the interval 1.0× {10}-19{--}2× {10}-18 erg s-1 cm-2 at signal-to-noise ratio (S/N) = 4-30. The double-peaked Lyα emission with {{∆ }}v({red}-{blue})=280(±7) km s-1 and de-lensed fluxes {2.4}({blue)}| {8.5}({red)}× {10}-18 erg s-1 cm-2 (S/N = {38}({blue)}| {110}({red)}) indicate a low column density of neutral hydrogen gas consistent with a highly ionized interstellar medium as also inferred from the large [O III]λ 5007/ [O II]λ 3727 \gt \quad 10 ratio. We detect C IV λ 1548,1550 resonant doublet in emission, each component with {FWHM}≲ 45 km s-1 and redshifted by +51(±10) km s-1 relative to the systemic redshift. We interpret this as nebular emission tracing an expanding optically thin interstellar medium. Both C IV λ 1548,1550 and He II λ 1640 suggest the presence of hot and massive stars (with a possible faint active galactic nucleus). The ultraviolet slope is remarkably blue, β =-2.95+/- 0.20 ({F}λ ={λ }β ), consistent with a dust-free and young ≲20 Myr galaxy. Line ratios suggest an oxygen abundance 12 + log(O/H)\quad \lt \quad 7.8. We are witnessing an early episode of star formation in which a relatively low N H I and negligible dust attenuation might favor a leakage of ionizing radiation. This galaxy currently represents a unique low-luminosity reference object for future studies of the reionization epoch with the James Webb Space Telescope. Based on observations collected at the European Southern Observatory for Astronomical research in the Southern Hemisphere under ESO programs P095.A-0840, P095.A-0653, P186.A-0798.

We present an analysis of ultraviolet (UV) to near-infrared observations of the fast-declining Type Ia supernovae (SNe Ia) 2007on and 2011iv, hosted by the Fornax cluster member NGC 1404. The B-band light curves of SN 2007on and SN 2011iv are characterised by Δm15 (B) decline-rate values of 1.96 mag and 1.77 mag, respectively. Although they have similar decline rates, their peak B- and H-band magnitudes differ by ~ 0.60 mag and ~0.35 mag, respectively. After correcting for the luminosity vs. decline rate and the luminosity vs. colour relations, the peak B-band and H-band light curves provide distances that differ by ~ 14% and ~ 9%, respectively. These findings serve as a cautionary tale for the use of transitional SNe Ia located in early-type hosts in the quest to measure cosmological parameters. Interestingly, even though SN 2011iv is brighter and bluer at early times, by three weeks past maximum and extending over several months, its B - V colour is 0.12 mag redder than that of SN 2007on. To reconcile this unusual behaviour, we turn to guidance from a suite of spherical one-dimensional Chandrasekhar-mass delayed-detonation explosion models. In this context, 56Ni production depends on both the so-called transition density and the central density of the progenitor white dwarf. To first order, the transition density drives the luminosity-width relation, while the central density is an important second-order parameter. Within this context, the differences in the B - V colour evolution along the Lira regime suggest that the progenitor of SN 2011iv had a higher central density than SN 2007on., Instituto de Astrofísica de La Plata, Facultad de Ciencias Astronómicas y Geofísicas

International audience; We present an analysis of cool outflowing gas around galaxies, traced by Mg-II absorption lines in the coadded spectra of a sample of 486 zCOSMOS galaxies at 1 \textless= z \textless= 1.5. These galaxies span a range of stellar masses (9.45 \textless= log(10)[M-*/M-circle dot] \textless= 10.7) and star formation rates (0.14 \textless= log(10)[SFR/M-circle dot yr(-1)] \textless= 2.35). We identify the cool outflowing component in the Mg (II) absorption and find that the equivalent width of the outflowing component increases with stellar mass. The outflow equivalent width also increases steadily with the increasing star formation rate of the galaxies. At similar stellar masses, the blue galaxies exhibit a significantly higher outflow equivalent width as compared to red galaxies. The outflow equivalent width shows strong correlation with the star formation surface density (Sigma(SFR)) of the sample. For the disk galaxies, the outflow equivalent width is higher for the face-on systems as compared to the edge-on ones, indicating that for the disk galaxies, the outflowing gas is primarily bipolar in geometry. Galaxies typically exhibit outflow velocities ranging from -150 km s(-1) similar to -200 km s(-1) and, on average, the face-on galaxies exhibit higher outflow velocity as compared to the edge-on ones. Galaxies with irregular morphologies exhibit outflow equivalent width as well as outflow velocities comparable to face on disk galaxies. These galaxies exhibit mass outflow rates \textgreater5-7 M-circle dot yr(-1) and a mass loading factor (eta = (M) over dot(out)/SFR) comparable to the star formation rates of the galaxies.

The ISO and IUE spectra of the elliptical nebulae NGC2022, NGC6818 and IC4191 are presented. These spectra are combined with the spectra in the visual wavelength region to obtain a complete, extinction corrected, spectrum. The chemical composition of the nebulae is then calculated and compared to previous determinations. A discussion is also given of the exciting stars of the nebulae, and possible evolutionary effects.

The ISO and IUE spectra of the elliptical nebulae NGC 5882, IC 418 and IC 2165 are presented. These spectra are combined with the spectra in the visual wavelength region to obtain a complete, extinction corrected, spectrum. The chemical composition of the nebulae is then calculated and compared to previous determinations. A discussion is given of: (1) the recombination line abundances; (2) the exciting stars of the nebulae; and (3) possible evolutionary effects.

Infrared spectra taken with the Short Wavelength Spectrometer on board ISO and UV observations with IUE of planetary nebulae BD+303639 and NGC6543 are presented. The extinction derived using infrared lines for BD+303639 is EB-V = 0.34, slightly higher than previous determinations. For NGC6543 the extinction found from the hydrogen lines is EB-V = 0.07. Infrared, optical and ultraviolet data have been used to derive the physical parameters of the nebula. BD+303639 has an average T-e = 8500 K and Ne = 11 000 cm(-3). In the case of NGC6543 a T-e = 8200 K and N-e = 5000 cm(-3) have been found, in agreement with previous determinations. The element abundances have been derived and compared to those found in the Sun and O, B stars. This comparison gives a hint of the mass of the progenitor stars from which they evolved.

The infrared and ultraviolet spectra of planetary nebula NGC 2440 is presented. The observations were made respectively by the Infrared Space Observatory (ISO) and International Ultraviolet Explorer (IUE) These data, in conjunction with published optical observations have been used to derive electron temperature and density. A trend of electron temperature with ionization potential is found. In particular the electron temperature increases from 11000 to 18000 K with increasing IBM. The electron density has a constant value of 4500/cu cm in agreement with previous determination. The chemical abundance has been derived for the following elements; helium, carbon, nitrogen, oxygen, neon, sulfur and argon. The ionization correction factor turns out to be very small (almost unnecessary) for all species except sulfur.

We present the discovery of a weak radio galaxy from the Leiden Berkeley Deep Survey at a redshift of 2.390, the faint optical and IR counterpart of the steep-spectrum, compact radio source 53W002. Its lambda-dependent optical continuum morphology is compact with linear size approximately 10-35 kpc (H0 = 50, q0 = 0). In redshifted Ly-alpha, the galaxy is somewhat more extended (less-than-or-similar-to 67 kpc x 40 kpc). Its radio source is 7 times smaller than, and confined by, the Ly-alpha gas. It shows alignment with the Ly-alpha gas and the best seeing optical continuum images.We present nine-band photometry (Ly-alpha U BgriJHK) for the galaxy as well as surrounding objects. The source 53W002 is not variable on time scales of years, in either radio or optical. We compare its rest-frame UV continuum with IUE spectra of various nearby galaxies with relatively recent starbursts, and nearby active galactic nuclei (AGNs). The C IV/Ly-alpha and N v/Ly-alpha ratios suggest that 53W002 has a Seyfert 1-like AGN, and constrain the nonthermal component to be approximately 35% of the observed UV continuum.Several independent age estimates yield a consistent value of 0.25-0.32 Gyr: (1) its small 4000 angstrom break or UV-visual continuum amplitude compared with nearby galaxies; (2) a best model fit to the downturn of its UV spectrum below approximately 2000 angstrom; (3) limits from the lack of detected stellar absorption features; (4) its total stellar mass (from its V- and K-band luminosity) compared with its SFR [from W-lambda (Ly-alpha, z = 0)]. These parameters together suggest that at z = 2.390, 53W002 had processed only a few times 10(11) M. into stars, significantly less than most powerful radio galaxies have converted into stars at z approximately 2-3.8. Hence, star formation in 53W002 has proceeded slower, and started at a later epoch, than in the most powerful high-redshift radio galaxies.The available data are consistent with 53W002 being a genuinely young (radio) galaxy seen at z = 2.390 during its first major starburst. It likely started forming most of its current stars at redshifts 2.5-3.0 (for H0 = 50-100, q0 = 0.0-0.5). This suggests that (radio) galaxies do not form the bulk of their stars coevally, but start doing so over a wide range of cosmic time.

Decreasing trends of total ozone affect mainly solar ultraviolet (UV) levels at ground level with adverse effects on the biosphere. Highly accurate measurements of solar UV irradiance have become an important issue to assess UV trends. To detect these trends stations with well calibrated instruments, with long-term stability and Quality Assurance (QA)/ Quality Control (QC) carefully followed procedures, are necessary. The Solar Radiometry Observatory of Rome, University “La Sapienza” (city center) is one of the stations regularly measuring UV irradiance in Italy. Measurements of UV spectral (290-325 nm) irradiance started in 1992, using Brewer MKIV 067. Measurements of total irradiance contained in the 280 - 320 nm waveband begun in 2000 with the YES UVB-1 broad-band radiometer. An investigation of the internal temperature dependence of the spectral responsivity to improve the quality of the Brewer UV data was carried out. The study was based on the analysis of responsivity files recorded during the years 2000-2002. Responsivities are provided by specific tests through a set of five 50 W quartz tungsten-halogen lamps, traceable to the standards of the National Institute of Standards and Technology (NIST). The lamp tests allow to measure any changes in the instrument response over time. It was observed that a decrease in the instrument's responsivity resulted from an increase of the internal temperature. A methodology based on a family of responsivity files at different temperature intervals is proposed to allow correction of UV irradiances using the responsivity file at the corresponding temperatures. The mean percentage differnce between temperature corrected and non-corrected Brewer data varies from 0.8% to 1.5% over an internal temperature of 8°C-42°C. In addition the results of a field evaluation in Rome between Brewer 067 and two temperature stabilized instruments, a broad-band radiometer (YES UVB-1) and a moderate bandwidth multichannel radiometer (Biospherical GUV-511C) were analyzed using temperature corrected spectral measurements.

We present the discovery of a weak radio galaxy from the Leiden Berkeley Deep Survey at a redshift of 2.390, the faint optical and IR counterpart of the steep-spectrum, compact radio source 53W002. Its lambda-dependent optical continuum morphology is compact with linear size approximately 10-35 kpc (H0 = 50, q0 = 0). In redshifted Ly-alpha, the galaxy is somewhat more extended (less-than-or-similar-to 67 kpc x 40 kpc). Its radio source is 7 times smaller than, and confined by, the Ly-alpha gas. It shows alignment with the Ly-alpha gas and the best seeing optical continuum images. We present nine-band photometry (Ly-alpha U BgriJHK) for the galaxy as well as surrounding objects. The source 53W002 is not variable on time scales of years, in either radio or optical. We compare its rest-frame UV continuum with IUE spectra of various nearby galaxies with relatively recent starbursts, and nearby active galactic nuclei (AGNs). The C IV/Ly-alpha and N v/Ly-alpha ratios suggest that 53W002 has a Seyfert 1-like AGN, and constrain the nonthermal component to be approximately 35% of the observed UV continuum. Several independent age estimates yield a consistent value of 0.25-0.32 Gyr: (1) its small 4000 angstrom break or UV-visual continuum amplitude compared with nearby galaxies; (2) a best model fit to the downturn of its UV spectrum below approximately 2000 angstrom; (3) limits from the lack of detected stellar absorption features; (4) its total stellar mass (from its V- and K-band luminosity) compared with its SFR [from W-lambda (Ly-alpha, z = 0)]. These parameters together suggest that at z = 2.390, 53W002 had processed only a few times 10(11) M. into stars, significantly less than most powerful radio galaxies have converted into stars at z approximately 2-3.8. Hence, star formation in 53W002 has proceeded slower, and started at a later epoch, than in the most powerful high-redshift radio galaxies. The available data are consistent with 53W002 being a genuinely young (radio) galaxy seen at z = 2.390 during its first major starburst. It likely started forming most of its current stars at redshifts 2.5-3.0 (for H0 = 50-100, q0 = 0.0-0.5). This suggests that (radio) galaxies do not form the bulk of their stars coevally, but start doing so over a wide range of cosmic time.