Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userSpitzer observations of extended Lyman-alpha Clouds in the SSA22 field
117
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We present the results of a Spitzer IRAC and MIPS 24 micron study of extended Lyman-alpha clouds (or Lyman-alpha Blobs, LABs) within the SSA22 filamentary structure at z = 3.09. We detect 6/26 LABs in all IRAC filters, four of which are also detected at 24 micron, and find good correspondence with the 850 micron measurements of Geach et al. 2005. An analysis of the rest-frame ultraviolet, optical, near- and mid-infrared colors reveals that these six systems exhibit signs of nuclear activity (AGN)and/or extreme star formation. Notably, they have properties that bridge galaxies dominated by star formation (Lyman-break galaxies; LBGs) and those with AGNs (LBGs classified as QSOs). The LAB systems not detected in all four IRAC bands, on the other hand, are, as a group, consistent with pure star forming systems, similar to the majority of the LBGs within the filament. These results indicate that the galaxies within LABs do not comprise a homogeneous population, though they are also consistent with scenarios in which the gas halos are ionized through a common mechanism such as galaxy-scale winds driven by the galaxies within them, or gravitational heating of the collapsing cloud itself.
rate research
Read More
We present the results of an ultradeep, narrowband imaging survey for Lyman-continuum (LyC) emission at z~3 in the SSA22a field. We employ a custom narrowband filter centered at 3640A (NB3640), which probes the LyC region for galaxies at z>3.06. We also analyze new and archival NB4980 imaging tuned to the wavelength of the Lya emission line at z=3.09, and archival broadband B, V, and R images of the non-ionizing UV continuum. Our NB3640 images contain 26 z>3.06 Lyman Break Galaxies (LBGs) as well as a set of 130 Lya emitters (LAEs), identified by their excess NB4980 flux relative to the BV continuum. Six LBGs and 28 LAEs are detected in the NB3640 image. LBGs appear to span a range of NB3640-R colors, while LAEs appear bimodal in their NB3640-R properties. We estimate average UV to LyC flux density ratios, corrected for foreground contamination and intergalactic medium absorption, finding <F_{UV}/F_{LyC}>^{LBG} = 11.3^{+10.3}_{-5.4}, which implies a LBG LyC escape fraction f_{esc}^{LyC} ~ 0.1, and <F_{UV}/F_{LyC}>^{LAE} = 2.2^{+0.9}_{-0.6}. The strikingly blue LAE flux density ratios defy interpretation in terms of standard stellar population models. Assuming <F_{UV}/F_{LyC}>^{LBG} applies down to L=0.1L*, we estimate a galaxy contribution to the intergalactic hydrogen ionization rate that is consistent with independent estimates based on the Lya forest opacity at z~3. If we assume that <F_{UV}/F_{LyC}>^{LAE} holds at the faintest luminosities, the galaxy contribution significantly exceeds that inferred from the Lya forest. Further follow-up study of these faint LAEs is crucial, given the potentially important contribution similar objects make to the process of reionization. (Abridged)
We have used the SAURON panoramic integral field spectrograph to study the structure of the Ly-alpha emission-line halo, LAB1, surrounding the sub-millimeter galaxy SMM J221726+0013. This emission-line halo was discovered during a narrow-band imaging survey of the z=3.1 large-scale structure in the SSA22 region. Our observations trace the emission halo out to almost 100 kpc from the sub-millimeter source and identify two distinct Ly-alpha `mini-haloes around the nearby Lyman-break galaxies. The main emission region has a broad line profile, with variations in the line profile seeming chaotic and lacking evidence for a coherent velocity structure. The data also suggests that Ly-alpha emission is suppressed around the sub-mm source. Interpretation of the line structure needs care because Ly-alpha may be resonantly scattered, leading to complex radiative transfer effects, and we suggest that the suppression in this region arises because of such effects. We compare the structure of the central emission-line halo with local counter-parts, and find that the emission line halo around NGC 1275 in the Perseus cluster may be a good local analogue, although the high redshift halo is factor of ~100 more luminous and appears to have higher velocity broadening. Around the Lyman-break galaxy C15, the emission line is narrower, and a clear shear in the emission wavelength is seen. A plausible explanation for the line profile is that the emission gas is expelled from C15 in a bipolar outflow, similar to that seen in M82.
We investigate the clustering properties of 13 QSO lines of sight in flat space, with average redshifts from z~2 to 4. We estimate the 1-D power spectrum and the integral density of neighbours, and discuss their variation with respect to redshift and column density. We compare the results with standard CDM models, and estimate the power spectrum of Lyman-alpha clustering as a function both of redshift and column density. We find that a) there is no significant periodicity or characteristic scale; b) the clustering depends both on column density and redshift; c) the clustering increases linearly only if at the same time the HI column density decreases strongly with redshift. The results remain qualitatively the same assuming an open cosmological model.
Hydrogen Lyman-$alpha$ (Ly$alpha$) emission has been one of the major observational probes for the high redshift universe, since the first discoveries of high-$z$ Ly$alpha$ emitting galaxies in the late 1990s. Due to the strong Ly$alpha$ emission originated by resonant scattering and recombination of the most-abundant element, Ly$alpha$ observations witness not only HII regions of star formation and AGN but also diffuse HI gas in the circum-galactic medium (CGM) and the inter-galactic medium (IGM). Here we review Ly$alpha$ sources, and present theoretical interpretations reached to date. We conclude that: 1) A typical Ly$alpha$ emitter (LAE) at $zgtrsim 2$ with a $L^*$ Ly$alpha$ luminosity is a high-$z$ counterpart of a local dwarf galaxy, a compact metal-poor star-forming galaxy (SFG) with an approximate stellar (halo) mass and star-formation rate of $10^{8-9} M_odot$ ($10^{10-11} M_odot$) and $1-10 M_odot$ yr$^{-1}$, respectively; 2) High-$z$ SFGs ubiquitously have a diffuse Ly$alpha$ emitting halo in the CGM extending to the halo virial radius and beyond; 3) Remaining neutral hydrogen at the epoch of reionization makes a strong dimming of Ly$alpha$ emission for galaxies at $z>6$ that suggest the late reionization history. The next generation large telescope projects will combine Ly$alpha$ emission data with HI Ly$alpha$ absorptions and 21cm radio data that map out the majority of hydrogen (HI+HII) gas, uncovering the exchanges of i) matter by outflow/inflow and ii) radiation, relevant to cosmic reionization, between galaxies and the CGM/IGM.
We search for bright Ly$rm alpha$ emitters among Spitzer SMUVS galaxies at z > 2.9 with homogeneous MUSE data. Although it only covers a small region of COSMOS, MUSE has the unique advantage of providing spectral information over the entire field, without the need of target pre-selection. This gives an unbiased detection of all the brightest Ly$rm alpha$ emitters among SMUVS sources, which by design are stellar-mass selected galaxies. Within the studied area, ~14% of the SMUVS galaxies at z > 2.9 have Ly$rm alpha$ fluxes F$rm _lambda$ > 7 x 10$^{-18}$ erg s$^{-1}$ cm$^{-2}$. These Ly$rm alpha$ emitters are characterized by three types of emission, 47% show a single line profile, 19% present a double peak or a blue bump and 31% show a red tail. One object (3%) shows both a blue bump and a red tail. We also investigate the spectral energy distribution (SED) properties of the SMUVS MUSE-detected galaxies and MUSE non-detections. After stellar-mass matching both populations, we find that MUSE detected galaxies have generally lower extinction than SMUVS-only objects, while there is no clear intrinsic difference in the mass and age distributions. For the MUSE-detected SMUVS galaxies, we compare the instantaneous SFR lower limit given by Ly$rm alpha$ flux with its past average derived from SED fitting, and find evidence for rejuvenation in some of our oldest objects. We also study the spectra of those Ly$rm alpha$ emitters which are not detected in SMUVS in the same field. We find different distributions of the emission line profiles, which could be ascribed to the fainter Ly$rm alpha$ luminosities of the MUSE-only sources and an intrinsically different mass distribution. Finally, we search for the presence of galaxy associations. MUSEs integral coverage is 20 times more likely to find associations than all other existing spectral data in COSMOS, biased by target pre-selection.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
