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Register a new userA high dust emissivity index beta for a CO-faint galaxy in a filamentary Lyman-alpha nebula at z=3.1
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We present CO J=4-3 line and 3 mm dust continuum observations of a 100 kpc-scale filamentary Ly{alpha} nebula (SSA22 LAB18) at z=3.1 using the Atacama Large Millimeter/submillimeter Array (ALMA). We detected the CO J=4-3 line at a systemic z(CO)=3.093 {pm} 0.001 at 11 {sigma} from one of the ALMA continuum sources associated with the Ly{alpha} filament. We estimated the CO J=4-3 luminosity of LCO(4-3)=(2.3pm0.2)x10^9 K km s^{-1} pc^2 for this CO source, which is one order of magnitude smaller than those of typical z>1 dusty star-forming galaxies (DSFGs) of similar far-infrared luminosity L(IR)~10^{12} Lsun. We derived a molecular gas mass of Mgas=(4.4^{+0.9}_{-0.6})x10^9 Msun and a star-formation rate of SFR=270pm160 Msun yr^{-1}. We also estimated a gas depletion time of {tau}(dep)=17pm10 Myr, being shorter than those of typical DSFGs. It is suggested that this source is in a transition phase from DSFG to a gas-poor, early-type galaxy. From ALMA to Herschel multi-band dust continuum observations, we measured a dust emissivity index {beta}=2.3pm0.2, which is similar to those of local gas-poor, early-type galaxies. Such a high {beta} can be reproduced by specific chemical compositions for interstellar dust at the submillimeter wavelengths from recent laboratory experiments. ALMA CO and multi-band dust continuum observations can constrain the evolutionary stage of high-redshift galaxies through {tau}(dep) and {beta}, and thus we can investigate dust chemical compositions even in the early Universe.
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We report the result from observations conducted with the Atacama Large Millimeter/submillimeter Array (ALMA) to detect [CII] 158 um fine structure line emission from galaxies embedded in one of the most spectacular Lyman-alpha blobs (LABs) at z=3.1, SSA22-LAB1. Of three dusty star-forming galaxies previously discovered by ALMA 860 um dust continuum survey toward SSA22-LAB1, we detected the [CII] line from one, LAB1-ALMA3 at z=3.0993+/-0.0004. No line emission was detected, associated with the other ALMA continuum sources or from three rest-frame UV/optical selected z_spec~3.1 galaxies within the field of view. For LAB1-ALMA3, we find relatively bright [CII] emission compared to the infrared luminosity (L_[CII]/L_[CII]) and an extremely high [CII] 158 um and [NII] 205 um emission line ratio (L_[CII]/L_[NII]>55). The relatively strong [CII] emission may be caused by abundant photodissociation regions and sub-solar metallicity, or by shock heating. The origin of the unusually strong [CII] emission could be causally related to the location within the giant LAB, although the relationship between extended Lyman-alpha emission and ISM conditions of associated galaxies is yet to be understand.
We present deep optical spectroscopy of an extended Ly$alpha$ emission-line blob located in an over-dense region at redshift $z approx 3.1$; `blob 1 of Steidel et al. (2000). The origin of such Ly$alpha$ blobs has been debated for some time; two of the most plausible models are (1) that it comes from a dust-enshrouded, extreme starburst galaxy with a large-scale galactic outflow (superwind/hyperwind) or (2) that it is the cooling radiation of proto-galaxies in dark matter halos. Examination of the kinematic properties of the Ly$alpha$ emission-line gas should allow us to determine its nature. With this motivation, we performed optical spectroscopy of `blob 1 using the Subaru Telescope, and found that its kinematic properties can be well explained in terms of superwind activity.
We present spectroscopic measurements of the [OIII] emission line from two subregions of strong Lyman-alpha emission in a radio-quiet Lyman-alpha blob (LAB). The blob under study is LAB1 (Steidel et al. 2000) at z ~ 3.1, and the [OIII] detections are from the two Lyman break galaxies embedded in the blob halo. The [OIII] measurements were made with LUCIFER on the 8.4m Large Binocular Telescope and NIRSPEC on 10m Keck Telescope. Comparing the redshift of the [OIII] measurements to Lyman-alpha redshifts from SAURON (Weijmans et al. 2010) allows us to take a step towards understanding the kinematics of the gas in the blob. Using both LUCIFER and NIRSPEC we find velocity offsets between the [OIII] and Lyman-alpha redshifts that are modestly negative or consistent with 0 km/s in both subregions studied (ranging from -72 +/- 42 -- +6 +/- 33 km/s). A negative offset means Lyman-alpha is blueshifted with respect to [OIII], a positive offset then implies Lyman-alpha is redshifted with respect to [OIII]. These results may imply that outflows are not primarily responsible for Lyman alpha escape in this LAB, since outflows are generally expected to produce a positive velocity offset (McLinden et al. 2011). In addition, we present an [OIII] line flux upper limit on a third region of LAB1, a region that is unassociated with any underlying galaxy. We find that the [OIII] upper limit from the galaxy-unassociated region of the blob is at least 1.4 -- 2.5 times fainter than the [OIII] flux from one of the LBG-associated regions and has an [OIII] to Lyman-alpha ratio measured at least 1.9 -- 3.4 times smaller than the same ratio measured from one of the LBGs.
We report the detection of a large ($sim90$ kpc) and luminous $mathrm{Lyalpha}$ nebula [$Lmathrm{_{Lyalpha}}$ = $(6.80pm0.08)times 10^{44}$] $rm{,erg,s^{-1}}$ around an optically faint (r$>23$ mag) radio galaxy M1513-2524 at $zmathrm{_{em}}$=3.132. The double-lobed radio emission has an extent of 184 kpc, but the radio core, i.e., emission associated with the active galactic nucleus (AGN) itself, is barely detected. This object was found as part of our survey to identify high-$z$ quasars based on Wide-field Infrared Survey Explorer (WISE) colors. The optical spectrum has revealed $mathrm{Lyalpha}$, NV, CIV and HeII emission lines with a very weak continuum. Based on long-slit spectroscopy and narrow band imaging centered on the $mathrm{Lyalpha}$ emission, we identify two spatial components: a compact component with high velocity dispersion ($sim 1500$$rm{,km,s^{-1}}$) seen in all three lines, and an extended component, having low velocity dispersion (i.e., 700-1000$rm{,km,s^{-1}}$). The emission line ratios are consistent with the compact component being in photoionization equilibrium with an AGN. We also detect spatially extended associated $mathrm{Lyalpha}$ absorption, which is blue-shifted within 250-400$rm{,km,s^{-1}}$ of the $mathrm{Lyalpha}$ peak. The probability of $mathrm{Lyalpha}$ absorption detection in such large radio sources is found to be low ($sim$10%) in the literature. M1513-2524 belongs to the top few percent of the population in terms of $mathrm{Lyalpha}$ and radio luminosities. Deep integral field spectroscopy is essential for probing this interesting source and its surroundings in more detail.
Context. Searching for high-redshift galaxies is a field of intense activity in modern observational cosmology that will continue to grow with future ground-based and sky observatories. Over the last few years, a lot has been learned about the high-z Universe. Aims. Despite extensive Ly-alpha Blobs (LAB) surveys from low to high redshifts, giant LABs over 100 kpc have been found mostly at z~2-4. This redshift range is coincident with the transition epoch of galactic gas-circulation processes from inflows to outflows at z~2.5-3. This suggests that the formation of giant LABs may be related to a combination of gas inflows and outflows. Their extreme youth makes them interesting objects in the study of galaxy formation as they provide insight into some of the youngest known highly star forming galaxies, with only modest time investments using ground-based telescopes. Methods. Systematic narrow-band Ly-alpha nebula surveys are ongoing, but they are limited in their covered redshift range and their comoving volume. This poses a significant problem when searching for such rare sources. To address this problem, we developed a systematic searching tool, ATACAMA (A Tool for seArChing for lArge LyMan Alpha nebulae) designed to find large Ly-alpha nebulae at any redshift within deep multi-wavelength broad-band imaging. Results. We identified a Ly-alpha nebula candidate at zphot~3.3 covering an isophotal area of 29.4sq.arcsec. Its morphology shows a bright core and a faint core which coincides with the morphology of previously known Ly-alpha blobs. A first estimation of the Ly-alpha equivalent width and line flux agree with the values from the study led by several groups.
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