Detect Lyα Emission Research Articles

SILVERRUSH. XII. Intensity Mapping for Lyα Emission Extending over 100–1000 Comoving Kpc around z ∼ 2−7 LAEs with Subaru HSC-SSP and CHORUS Data

We conduct intensity mapping to probe for extended diffuse Lyα emission around Lyα emitters (LAEs) at z ∼2−7, exploiting very deep (∼26 mag at 5σ) and large-area (∼4.5 deg2) Subaru/Hyper Suprime-Cam narrowband (NB) images and large LAE catalogs consisting of a total of 1540 LAEs at z = 2.2, 3.3, 5.7, and 6.6 obtained by the HSC-SSP and CHORUS projects. We calculate the spatial correlations of these LAEs with ∼1–2 billion pixel flux values of the NB images, deriving the average Lyα surface brightness (SBLyα ) radial profiles around the LAEs. By carefully estimating systematics such as fluctuations of sky background and point-spread functions, we detect Lyα emission at 100–1000 comoving kpc around z = 3.3 and 5.7 LAEs at the 3.2σ and 3.7σ levels, respectively, and tentatively (=2.0σ) at z = 6.6. The emission is as diffuse as ∼10−20–10−19 erg s−1 cm−2 arcsec−2 and extended beyond the virial radius of a dark matter halo with a mass of 1011 M ⊙. While the observed SBLyα profiles have similar amplitudes at z = 2.2–6.6 within the uncertainties, the intrinsic SBLyα profiles (corrected for the cosmological dimming effect) increase toward high redshifts. This trend may be explained by increasing hydrogen gas density due to the evolution of the cosmic volume. Comparisons with theoretical models suggest that extended Lyα emission around an LAE is powered by resonantly scattered Lyα photons in the CGM and IGM that originate from the inner part of the LAE and/or neighboring galaxies around the LAE.

Variation in the Stellar Initial Mass Function from the Chromospheric Activity of M Dwarfs in Early-type Galaxies

Abstract Mass measurements and absorption-line studies indicate that the stellar initial mass function (IMF) is bottom-heavy in the central regions of many early-type galaxies, with an excess of low-mass stars compared to the IMF of the Milky Way. Here we test this hypothesis using a method that is independent of previous techniques. Low-mass stars have strong chromospheric activity characterized by nonthermal emission at short wavelengths. Approximately half of the UV flux of M dwarfs is contained in the λ1215.7 Lyα line, and we show that the total Lyα emission of an early-type galaxy is a sensitive probe of the IMF with a factor of ∼2 flux variation in response to plausible variations in the number of low-mass stars. We use the Cosmic Origins Spectrograph on the Hubble Space Telescope to measure the Lyα line in the centers of the massive early-type galaxies NGC 1407 and NGC 2695. We detect Lyα emission in both galaxies and demonstrate that it originates in stars. We find that the Lyα to i-band flux ratio is a factor of 2.0 ± 0.4 higher in NGC 1407 than in NGC 2695, in agreement with the difference in their IMFs as previously determined from gravity-sensitive optical absorption lines. Although a larger sample of galaxies is required for definitive answers, these initial results support the hypothesis that the IMF is not universal but varies with environment.

Discovery of a Damped Lyα Galaxy at z ∼ 3 toward the Quasar SDSS J011852+040644

Abstract We report the detection of the host galaxy of a damped Lyα system (DLA) with log N(H i) [cm−2] = 21.0 ± 0.10 at z ≈ 3.0091 toward the background quasar SDSS J011852+040644 using the Palomar Cosmic Web Imager at the Hale (P200) telescope. We detect Lyα emission in the dark core of the DLA trough at a 3.3σ confidence level, with Lyα luminosity of L Lyα = (3.8 ± 0.8) × 1042 erg s−1, corresponding to a star formation rate of ≳2 M ⊙ yr−1 (considering a lower limit on Lyα escape fraction f esc Ly α ∼ 2 % ) as typical for Lyman break galaxies at these redshifts. The Lyα emission is blueshifted with respect to the systemic redshift derived from metal absorption lines by 281 ± 43 km s−1. The associated galaxy is at very small impact parameter of ≲12 kpc from the background quasar, which is in line with the observed anticorrelation between column density and impact parameter in spectroscopic searches tracing the large-scale environments of DLA host galaxies.

The CGM at Cosmic Noon with KCWI: Outflows from a Star-forming Galaxy at z = 2.071

Abstract We present the first results from our “CGM at Cosmic Noon with KCWI” program to study gas flows in the circumgalactic medium (CGM) at z = 2–3. Combining the power of a high-resolution VLT/UVES quasar spectrum, a Hubble Space Telescope/Advanced Camera for Surveys image, and integral field spectroscopy with Keck/KCWI (Keck Cosmic Web Imager), we detected Lyα emission from a 1.7L * galaxy at z gal = 2.0711 associated with a Lyman limit system with weak Mg ii (W r (2796) = 0.24 Å) in quasar field J143040+014939. The galaxy is star-forming (SFRFUV = 37.8 M ⊙ yr−1) and clumpy: either an edge-on disk (i = 85°) or, less likely, a major merger. The background quasar probes the galaxy at an impact parameter of D = 66 kpc along the projected galaxy minor axis (Φ = 89°). From photoionization modeling of the absorption system, we infer a total line-of-sight CGM metallicity of . The absorption system is roughly kinematically symmetric about z gal, with a full Mg ii velocity spread of ∼210 km s−1. Given the galaxy–quasar orientation, CGM metallicity, and gas kinematics, we interpret this gas as an outflow that has likely swept up additional material. By modeling the absorption as a polar outflow cone, we find the gas is decelerating with average radial velocity V out = 109–588 km s−1 for half-opening angles of θ 0 = 14°–75°. Assuming a constant V out, it would take on average t out ∼ 111–597 Myr for the gas to reach 66 kpc. The outflow is energetic, with a mass outflow rate of M ⊙ yr−1 and mass loading factor of η < 1.4 ± 1.0. We aim to build a sample of ∼50 Mg ii absorber–galaxy pairs at this epoch to better understand gas flows when they are most actively building galaxies.

Discovery of a z = 7.452 High Equivalent Width Lyα Emitter from the Hubble Space Telescope Faint Infrared Grism Survey

Abstract We present the results of an unbiased search for Lyα emission from continuum-selected 5.6 < z < 8.7 galaxies. Our data set consists of 160 orbits of G102 slitless grism spectroscopy obtained with the Hubble Space Telescope(HST)/WFC3 as part of the Faint Infrared Grism Survey (FIGS; PI: Malhotra), which obtains deep slitless spectra of all sources in four fields, and was designed to minimize contamination in observations of previously identified high-redshift galaxy candidates. The FIGS data can potentially spectroscopically confirm the redshifts of galaxies, and as Lyα emission is resonantly scattered by neutral gas, FIGS can also constrain the ionization state of the intergalactic medium during the epoch of reionization. These data have sufficient depth to detect Lyα emission in this epoch, as Tilvi et al. have published the FIGS detection of previously known Lyα emission at z = 7.51. The FIGS data use five separate roll angles of HST to mitigate the contamination by nearby galaxies. We created a method that accounts for and removes the contamination from surrounding galaxies and also removes any dispersed continuum light from each individual spectrum. We searched for significant (>4σ) emission lines using two different automated detection methods, free of any visual inspection biases. Applying these methods on photometrically selected high-redshift candidates between 5.6 < z < 8.7, we find two emission lines, one previously published by Tilvi et al., (2016) and a new line at 1.028 μm, which we identify as Lyα at z = 7.452 ± 0.003. This newly spectroscopically confirmed galaxy has the highest Lyα rest-frame equivalent width (EWLyα ) yet published at z > 7 (140.3 ± 19.0 Å).

The MUSE Hubble Ultra Deep Field Survey

We report the detection of extended Lyα haloes around 145 individual star-forming galaxies at redshifts 3 ≤ z ≤ 6 in the Hubble Ultra Deep Field observed with the Multi-Unit Spectroscopic Explorer (MUSE) at ESO-VLT. Our sample consists of continuum-faint (− 15 ≥ MUV ≥ −22) Lyα emitters (LAEs). Using a 2D, two-component (continuum-like and halo) decomposition of Lyα emission assuming circular exponential distributions, we measure scale lengths and luminosities of Lyα haloes. We find that 80% of our objects having reliable Lyα halo measurements show Lyα emission that is significantly more extended than the UV continuum detected by HST (by a factor ≈4 to >20). The median exponential scale length of the Lyα haloes in our sample is ≈4.5 kpc with a few haloes exceeding 10 kpc. By comparing the maximal detected extent of the Lyα emission with the predicted dark matter halo virial radii of simulated galaxies, we show that the detected Lyα emission of our selected sample of Lyα emitters probes a significant portion of the cold circum-galactic medium of these galaxies (>50% in average). This result therefore shows that there must be significant HI reservoirs in the circum-galactic medium and reinforces the idea that Lyα haloes are ubiquitous around high-redshift Lyα emitting galaxies. Our characterization of the Lyα haloes indicates that the majority of the Lyα flux comes from the halo (≈65%) and that their scale lengths seem to be linked to the UV properties of the galaxies (sizes and magnitudes). We do not observe a significant Lyα halo size evolution with redshift, although our sample for z> 5 is very small. We also explore the diversity of the Lyα line profiles in our sample and we find that the Lyα lines cover a large range of full width at half maximum (FWHM) from 118 to 512 km s-1. While the FWHM does not seem to be correlated to the Lyα scale length, most compact Lyα haloes and those that are not detected with high significance tend to have narrower Lyα profiles (<350 km s-1). Finally, we investigate the origin of the extended Lyα emission but we conclude that our data do not allow us to disentangle the possible processes, i.e. scattering from star-forming regions, fluorescence, cooling radiation from cold gas accretion, and emission from satellite galaxies.

A NEW CONSTRAINT ON THE Lyα FRACTION OF UV VERY BRIGHT GALAXIES AT REDSHIFT 7

ABSTRACT We study the extent to which very bright ( ) Lyman-break-selected galaxies at redshifts display detectable Lyα emission. To explore this issue, we obtained follow-up optical spectroscopy of 9 galaxies from a parent sample of 24 galaxy candidates selected from the 1.65 deg2 COSMOS-UltraVISTA and SXDS-UDS survey fields using the latest near-infrared public survey data, and new ultra-deep Subaru z′-band imaging (which we also present and describe in this paper). Our spectroscopy yielded only one possible detection of Lyα at z = 7.168 with a rest-frame equivalent width . The relative weakness of this line, combined with our failure to detect Lyα emission from the other spectroscopic targets, allows us to place a new upper limit on the prevalence of strong Lyα emission at these redshifts. For conservative calculation and to facilitate comparison with previous studies at lower redshifts, we derive a 1σ upper limit on the fraction of UV-bright galaxies at that display , which we estimate to be . This result may indicate a weak trend where the fraction of strong Lyα emitters ceases to rise, and possibly falls between z ≃ 6 and . Our results also leave open the possibility that strong Lyα may still be more prevalent in the brightest galaxies in the reionization era than their fainter counterparts. A larger spectroscopic sample of galaxies is required to derive a more reliable constraint on the neutral hydrogen fraction at based on the Lyα fraction in the bright galaxies.

Detection of emission lines fromz∼ 3 DLAs towards the QSO J2358+0149

Using VLT/X-shooter, we searched for emission line galaxies associated with four damped Lyman α systems (DLAs) and one sub-DLA at 2.73 ≤z ≤3.25 towards QSO J2358+0149. We detect [O iii] emission from a ‘low-cool’ DLA at zabs = 2.9791 (having log N(H i) = 21.69 ± 0.10, [Zn/H] = −1.83 ± 0.18) at an impact parameter of, ρ ∼ 12 kpc. The associated galaxy is compact with a dynamical mass of (1–6) × 109 M⊙, very high excitation ([O iii]/[O ii] and [O iii]/[Hβ] both greater than 10), 12+[O/H]≤8.5 and moderate star formation rate (SFR ≤2 M⊙ yr−1). Such properties are typically seen in the low-z extreme blue compact dwarf galaxies. The kinematics of the gas is inconsistent with that of an extended disc and the gas is part of either a large scale wind or cold accretion. We detect Lyα emission from the zabs = 3.2477 DLA [having log N(H i) = 21.12 ± 0.10 and [Zn/H] = −0.97 ± 0.13]. The Lyα emission is redshifted with respect to the metal absorption lines by 320 km s−1, consistent with the location of the red hump expected in radiative transport models. We derive SFR ∼0.2–1.7 M⊙ yr−1 and Lyα escape fraction of ≥10 per cent. No other emission line is detected from this system. Because the DLA has a small velocity separation from the quasar (∼500 km s−1) and the DLA emission is located within a small projected distance (ρ < 5 kpc), we also explore the possibility that the Lyα emission is being induced by the QSO itself. QSO-induced Lyα fluorescence is possible if the DLA is within a physical separation of 340 kpc to the QSO. Detection of stellar continuum light and/or the oxygen emission lines would disfavour this possibility. We do not detect any emission line from the remaining three systems.

Clustering of Lyα emitters around luminous quasars at z= 2-3: an alternative probe of reionization on galaxy formation

Narrow-band observations fail to detect Lyα emission within a volume centred on the z= 2.168 quasar PKS 0424–131. This is in contrast to surveys of Lyα emitters in the field at similar redshifts and flux limits, which indicate that tens of sources should be visible within the same volume. The observed difference indicates that the quasar environment has a significant influence on the observed density of Lyα emitters. To quantify this effect, we have constructed a semi-analytic model to simulate the effect of a luminous quasar on nearby Lyα emitters. We find the null detection around PKS 0424–131 implies that the minimum isothermal temperature of Lyα emitter host haloes is greater than (68 per cent level), corresponding to a virial mass of ∼1.2 × 1012 M⊙. This indicates that the intense ultraviolet emission of the quasar may be suppressing the star formation in nearby galaxies. Our study illustrates that low-redshift quasar environments may serve as a surrogate for studying the radiative suppression of galaxy formation during the epoch of reionization.

Molecular Gas in a Submillimeter Galaxy at z = 4.5: Evidence for a Major Merger at 1 Billion Years after the Big Bang

We report the detection of CO molecular line emission in the z = 4.5 millimeter-detected galaxy COSMOS J100054+023436 (hereafter J1000+0234) using the IRAM Plateau de Bure interferometer (PdBI) and NRAO's Very Large Array (VLA). The 12CO(4-3) line as observed with PdBI has a full line width of ~1000 km s−1, an integrated line flux of 0.66 Jy km s−1, and a CO luminosity of 3.2 × 1010 L☉. Comparison to the 3.3 σ detection of the CO(2-1) line emission with the VLA suggests that the molecular gas is likely thermalized to the J = 4–3 transition level. The corresponding molecular gas mass is 2.6 × 1010 M☉ assuming an ULIRG-like conversion factor. From the spatial offset of the red- and blueshifted line peaks and the line width a dynamical mass of 1.1 × 1011 M☉ is estimated assuming a merging scenario. The molecular gas distribution coincides with the rest-frame optical and radio position of the object while being offset by 0.5'' from the previously detected Lyα emission. J1000+0234 exhibits very typical properties for lower redshift (z ∼ 2) submillimeter galaxies (SMGs) and thus is very likely one of the long sought after high-redshift (z > 4) objects of this population. The large CO(4-3) line width taken together with its highly disturbed rest-frame UV geometry suggest an ongoing major merger about a billion years after the big bang. Given its large star formation rate (SFR) of >1000 M☉ yr−1 and molecular gas content this object could be the precursor of a "red and dead" elliptical observed at a redshift of z = 2.

Fluorescent Lyman α emission from gas near a QSO at redshift 4.28

We use integral field spectroscopy with the Gemini North Telescope to detect probable fluorescent Lyman a (Lya) emission from gas lying close to the luminous QSO PSS 2155+1358 at redshift 4.28. The emission is most likely coming not from primordial gas, but from a multiphase, chemically enriched cloud of gas lying about 50 kpc from the QSO. It appears to be associated with a highly ionized associated absorber seen in the QSO spectrum. With the exception of this gas cloud, the environment of the QSO is remarkably free of neutral hydrogen. We also marginally detect Lyα emission from a foreground subdamped Lya absorption-line system.

The mass-metallicity relation for high-redshift damped Ly$\alpha$ galaxies

We used our database of ESO VLT-UVES spectra of quasars to build up a sample of 67 damped Lyman-α (DLA) systems with redshifts 1.7 abs 1 . We find that there is a tight correlation between the two quantities, detected at the 5σ significance level. The existence of such a correlation, over more than two orders of magnitude spread in metallicity, is likely to be the consequence of an underlying mass-metallicity relation for the galaxies responsible for DLA absorption lines. The best-fit linear relation is [X/H]=(91.35 ± 0.11) log W 1 -(3.69 ± 0.18) with W 1 expressed in km -1 . While the slope of this velocity-metallicity relation is the same within uncertainties between the higher and the lower redshift bins of our sample, there is a hint of an increase in the intercept point of the relation with decreasing redshift. This suggests that galaxy halos of a given mass tend to become more metal-rich with time. Moreover, the slope of this relation is consistent with that of the luminosity-metallicity relation for local galaxies. The DLA systems having the lowest metallicities among the DLA population would therefore, on average, correspond to the galaxies having the lowest masses. In turn, these galaxies should have the lowest luminosities among the DLA galaxy population. This may explain the recent result that the few DLA systems with detected Lyα emission have higher than average metallicities.

Detection of Lyman-α emission from a DLA galaxy: Possible implications for a luminosity-metallicity relation at z = 2–3

In an ongoing programme to identify a sample of high z DLA galaxies we have found the long sought for of aL yα emitter seen in the centre of a broad DLA trough. This is the predicted textbook case of an intervening DLA galaxy if DLA galaxies are small, but would not be expected if intervening high redshift DLA galaxies have large gaseous disks. The Lyα flux is 5.4 +2 −0.8 × 10 −17 erg s −1 cm −2 similar to what has been found in previously known high z DLA galaxies. The impact parameter is found to be 0. �� 3 ± 0. �� 3. This is smaller than what was found in previous cases but still consistent with random sight- lines through absorbers with mean impact parameter ≈1 �� . Of the 24 DLAs targeted in the NICMOS imaging survey five have now been identified as Lyα emitters. The DLA galaxies with detected Lyα emission tend to have higher interstellar metallicities than those with undetected Lyα emission. This is plausibly explained as a consequence of a positive correlation between the Lyα line luminosities of the galaxies and their metallicities, although the present sample is too small for a definitive conclusion. The available observations of high-redshift DLA galaxies are also consistent with a negative correlation between Lyα equiv- alent widths and metallicities, as seen in nearby star-forming galaxies and usually attributed to the preferential absorption of Lyα photons by dust grains.

Hubble Space TelescopeImaging and Keck Spectroscopy ofz≈ 6i‐Band Dropout Galaxies in the Advanced Camera for Surveys GOODS Fields

We measure the surface density of i'-band dropout galaxies at z ~ 6 through wide-field Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) imaging and ultradeep Keck DEIMOS spectroscopy. Using deep HST ACS SDSS i' (F775W) and SDSS z' (F850LP) imaging from the Great Observatories Origins Deep Survey-North (GOODS-N; 200 arcmin2), we identify nine i'-drops satisfying (i'-z')AB > 1.5 to a depth of zimg1.gif = 25.6 (corresponding to Limg2.gif at z ~ 3). We use HK' imaging data to improve the fidelity of our sample, discriminating against lower redshift red galaxies and cool Galactic stars. Three i'-drops are consistent with M/L/T dwarf stars. We present ultradeep Keck DEIMOS spectroscopy of 10 objects from our combined GOODS-N and GOODS-S i'-drop sample. We detect Lyα emission at z = 5.83 from one object in the GOODS-S field, which lies only 8' (i.e., 3 himg3.gif Mpc) away from a previously confirmed z = 5.78 object. One possible Lyα emitter at z = 6.24 is found in the GOODS-N field (although identification of this spatially offset emission line is ambiguous). Using the rest-frame UV continuum from our six candidate z ~ 6 galaxies from the GOODS-N field, we determine a lower limit to the unobscured volume-averaged global star formation rate at z ~ 6 of (5.4 ± 2.2) × 10-4 h70 M☉ yr-1 Mpc-3. We find that the cosmic star formation density in Lyman break galaxies (LBGs) with unobscured star formation rates greater than 15 M☉ yr-1 falls by a factor of 8 between z ~ 3 and z ~ 6. Hence, the luminosity function of LBGs must evolve in this redshift interval: a constant integrated star formation density at z > 3 requires a much steeper faint-end slope, or a brighter characteristic luminosity. This result is in agreement with our previous measurement from the GOODS-S field, indicating that cosmic variance is not a dominant source of uncertainty.

The evolution of superbubbles and the detection of Ly in star-forming galaxies

The detection of Lyα emission in star-forming galaxies in different shapes and intensities (always smaller than predicted for case B recombination) has puzzled the astronomical community for more than a decade. Here we use two-dimensional calculations to follow the evolution of superbubbles and of the H ii regions generated by the output of UV photons from massive stars. We show the impact caused by massive star formation in the ISM of different galaxies and we look at the conditions required to detect Lyα emission from a nuclear H ii region, and the variety of profiles that may be expected as a function of time.

Nearby Young Dwarf Galaxies: Primordial Gas and Lyα Emission

We present Hubble Space Telescope UV spectrophotometry of three extremely metal-deficient blue compact dwarf (BCD) galaxies, SBS 0335-052 (Z ~ Z☉/40), Tol 65 (Z ~ Z☉/24), and T1214-277 (Z ~ Z☉/23). Broad damped Lyα absorption is seen in the first two BCDs. For SBS 0335-052, the H I column density derived by fitting the Lyα absorption profile is N(H I) = (7.0 ± 0.5) × 1021 cm-2, which is the highest H I column density derived thus far for a BCD and which is ~2 times larger than that in I Zw 18. As for Tol 65, N(H I) = (2.5 ± 1.0) × 1021 cm-2, which is also in the high range of H I column densities derived for BCDs and which is only ~1.4 times smaller than that in I Zw 18. The interstellar absorption line O I λ1302 has also been detected in both galaxies. Comparison with high-resolution quasar spectra implies that in SBS 0335-052, the O I λ1302 line, along with other heavy element interstellar absorption lines such as Si II λ1304 and S II λ1251, λ1254, and λ1259, are not saturated, which allows us to derive abundances. Assuming that these lines originate in the H I gas, we derive abundances of oxygen, silicon, and sulfur, respectively, as 37,000, 4000, and 116 times lower than the solar values. The oxygen abundance is a whole 37 times lower than in the neutral gas of I Zw 18. However, these highly discrepant deficiency factors of different elements suggest that the absorption lines are produced, not in the H I, but in the H II gas. Adopting that hypothesis, the derived abundances from the UV absorption lines are then consistent with that derived from the optical emission lines (Z ~ Z☉/40). The conclusion that the heavy element absorption lines originate in the H II region is supported by the detection of several systems of blueshifted S II λ1259, Si II λ1260, O I λ1302, Si II λ1304, and C II λ1335 absorption lines originating in fast-moving clouds with velocities up to ~1500 km s-1 and also by the presence of heavy element absorption lines with excited lower levels. If this conclusion holds, then the H I cloud in SBS 0335-052 is truly primordial, unpolluted by heavy elements. This would alleviate the need for postulating previous enrichment by widespread Population III stars and poses the problem of how such a cloud could last for a Hubble time without making stars before the present epoch. Because the O I λ1302 is likely to be saturated in Tol 65, we could derive only a lower limit for the oxygen abundance, ~6000 times lower than the solar value. Contrary to the situation in the two previous BCDs, a strong Lyα line is seen in the spectrum of T1214-277, which makes it the lowest metallicity BCD with detected Lyα emission. Its equivalent width of 70 A is the largest found in star-forming galaxies. The Lyα emission is not redshifted with respect to the H II gas velocity, so that the escape of Lyα photons in T1214-277 is not dictated by the velocity structure of the H I gas but probably by its porosity. The absence of Lyα emission in SBS 0335-052 and Tol 65 is probably caused by a combination of dust extinction, redistribution of the Lyα photons by multiple scattering over the whole area of the H I cloud, and the geometry of the cloud. The spectrum of SBS 0335-052 shows stellar Si IV λ1394 and λ1403 lines with P Cygni profiles, which suggests the presence of numerous hot supergiant stars. A strong stellar N V λ1240 line with a P Cygni profile is also seen in the spectrum of T1214-277, which suggests that a large population of massive (M 60 M☉) stars is present. The stellar wind terminal velocity is very low in SBS 0335-052, being only ~500 km s-1. It is higher, ~2000 km s-1 in T1214-277, in the low range of terminal velocities found for other BCDs. These BCDs are the two most metal-deficient galaxies known with P Cygni profiles. The presence of such profiles raises the question of how to set up a wind in stellar atmospheres devoid of heavy elements as in SBS 0335-052.

Extended Ly-alpha emission associated with 3C 294

view Abstract Citations (120) References (73) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Extended LY alpha Emission Associated with 3C 294 McCarthy, Patrick J. ; Spinrad, Hyron ; van Breugel, Wil ; Liebert, James ; Dickinson, Mark ; Djorgovski, S. ; Eisenhardt, Peter Abstract We report the discovery of a large cloud of ionized gas associated with the radio galaxy 3C 294 at a redshift of 1.786. The radio source is a powerful double with a weak core. We detect Lyα emission with a total monochromatic luminosity of L_Lyα_ = 7.6 x 10^44^ ergs s^-1^ extended over ~ 100 x 170 kpc. The emission-line cloud is highly elongated and is well aligned with the inner radio source axis. Long-slit spectra, taken along the major axis, show spatially extended emission lines of N V λ1240, C IV λ1550, He II λ1640, and C III λ1909. The extended Lyα emission shows a large, smooth velocity gradient (1500 km s^-1^) and large intrinsic line widths (700-2600 km s^-1^). The high-ionization lines, particularly C IV, show large velocity changes that are systematically different from those of Lyα. 3C 294 appears to be another, even more spectacular member of a class of powerful radio galaxies at high redshift typified by 3C 326.1. We discuss our observations from the point of view of star formation and the interaction of nuclear activity with ambient material. We consider two scenarios for the ionization of the Lyα cloud: ionization by a population of extremely massive stars and ionization by a nonthermal continuum from the radio nucleus. Stellar photoionization appears to be insufficient in both the total number of ionizing photons and its ability to produce highly ionized species. We propose that the 150 kpc cloud of gas is photoionized by a central nonstellar source. We detect a very red compact object at 2.2 micron coincident with the radio core. It is unclear whether the light from this object is primarily stellar or nonstellar. Publication: The Astrophysical Journal Pub Date: December 1990 DOI: 10.1086/169503 Bibcode: 1990ApJ...365..487M Keywords: Galactic Evolution; Galactic Radiation; Lyman Alpha Radiation; Radio Galaxies; Red Shift; Emission Spectra; Ionized Gases; Line Spectra; Astrophysics; GALAXIES: EVOLUTION; GALAXIES: INDIVIDUAL ALPHANUMERIC: 3C 294; GALAXIES: REDSHIFTS; RADIO SOURCES: GALAXIES full text sources ADS | data products SIMBAD (5) NED (1)