اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدA young star-forming galaxy at z = 3.5 with an extended Ly,$alpha$ halo seen with MUSE
95
0
0.0
(
0
)
تأليف
Vera Patricio
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
Spatially resolved studies of high redshift galaxies, an essential insight into galaxy formation processes, have been mostly limited to stacking or unusually bright objects. We present here the study of a typical (L$^{*}$, M$_star$ = 6 $times 10^9$ $M_odot$) young lensed galaxy at $z=3.5$, observed with MUSE, for which we obtain 2D resolved spatial information of Ly$alpha$ and, for the first time, of CIII] emission. The exceptional signal-to-noise of the data reveals UV emission and absorption lines rarely seen at these redshifts, allowing us to derive important physical properties (T$_esim$15600 K, n$_esim$300 cm$^{-3}$, covering fraction f$_csim0.4$) using multiple diagnostics. Inferred stellar and gas-phase metallicities point towards a low metallicity object (Z$_{mathrm{stellar}}$ = $sim$ 0.07 Z$_odot$ and Z$_{mathrm{ISM}}$ $<$ 0.16 Z$_odot$). The Ly$alpha$ emission extends over $sim$10 kpc across the galaxy and presents a very uniform spectral profile, showing only a small velocity shift which is unrelated to the intrinsic kinematics of the nebular emission. The Ly$alpha$ extension is $sim$4 times larger than the continuum emission, and makes this object comparable to low-mass LAEs at low redshift, and more compact than the Lyman-break galaxies and Ly$alpha$ emitters usually studied at high redshift. We model the Ly$alpha$ line and surface brightness profile using a radiative transfer code in an expanding gas shell, finding that this model provides a good description of both observables.
قيم البحث
اقرأ أيضاً
To identify the galaxies responsible for the reionization of the Universe, we must rely on the investigation of the Lyman Continuum (LyC) properties of z<5 star-forming galaxies, where we can still directly observe their ionizing radiation. We select
ed a sample of 201 star-forming galaxies from the Vimos Ultra Deep Survey at 3.5<z<4.3 to explore the validity of some of the proposed indirect indicators of LyC radiation. We created subsamples of galaxies with EWLya>70{AA}, Lya(ext)<5.7kpc, rUV<0.3kpc and |Dv Lya|<200km/s, stacked all the galaxies in each subsample and measured the flux density ratio fnu(895)/fnu(1470), that we consider to be a proxy for LyC emission. We compared these ratios to those obtained for the complementary samples. We find that the stacks of galaxies which are UV compact (rUV<0.3kpc) and have bright Lya emission (EWLya>70{AA}), have much higher LyC fluxes compared to the rest of the galaxy population in agreement with theoretical studies and previous observational works. We also find that galaxies with low Lya(ext) have the highest LyC flux: this new correlation seems even stronger than the correlations with high EWLya and small rUV. These results assume that the stacks from all the subsamples present the same statistical contamination from lower redshift interlopers. If we subtract a statistical contamination from low redshift interlopers obtained with dedicated Monte Carlo simulations, from the flux density ratios (fnu(895)/fnu(1470)) of the significant subsamples we find that these samples contain real LyC leaking flux with a very high probability, but the true average escape fractions remain uncertain. Our work indicates that galaxies with very high EWLya, small Lya(ext) and small rUV are very likely the best candidates to show LyC radiation at z=4 and could therefore be the galaxies that contributed more to reionization.
Recent theoretical models suggest that the early phase of galaxy formation could involve an epoch when galaxies are gas-rich but inefficient at forming stars: a dark galaxy phase. Here, we report the results of our MUSE (Multi Unit Spectroscopic Expl
orer) survey for dark galaxies fluorescently illuminated by quasars at $z>3$. Compared to previous studies which are based on deep narrow-band (NB) imaging, our integral field survey provides a nearly uniform sensitivity coverage over a large volume in redshift space around the quasars as well as full spectral information at each location. Thanks to these unique features, we are able to build control samples at large redshift distances from the quasars using the same data taken under the same conditions. By comparing the rest-frame equivalent width (EW$_{0}$) distributions of the Ly$alpha$ sources detected in proximity to the quasars and in control samples, we detect a clear correlation between the locations of high EW$_{0}$ objects and the quasars. This correlation is not seen in other properties such as Ly$alpha$ luminosities or volume overdensities, suggesting the possible fluorescent nature of at least some of these objects. Among these, we find 6 sources without continuum counterparts and EW$_{0}$ limits larger than $240,mathrm{AA}$ that are the best candidates for dark galaxies in our survey at $z>3.5$. The volume densities and properties, including inferred gas masses and star formation efficiencies, of these dark galaxy candidates are similar to previously detected candidates at $zapprox2.4$ in NB surveys. Moreover, if the most distant of these are fluorescently illuminated by the quasar, our results also provide a lower limit of $t=60$ Myr on the quasar lifetime.
We present deep MUSE integral-field unit (IFU) spectroscopic observations of the giant (~150 x 80 kpc) Ly-alpha halo around the z=4.1 radio galaxy TNJ J1338-1942. This 9-hr observation maps the two-dimensional kinematics of the Ly-alpha emission acro
ss the halo. We identify two HI absorbers which are seen against the Ly-alpha emission, both of which cover the full 150 x 80 kpc extent of the halo and so have covering fractions ~1. The stronger and more blue-shifted absorber (dv~1200 km/s) has dynamics that mirror that of the underlying halo emission and we suggest that this high column material (n(HI) ~ 10^19.4 /cm^2), which is also seen in CIV absorption, represents an out-flowing shell that has been driven by the AGN (or star formation) within the galaxy. The weaker (n(HI)~10^14 /cm^2) and less blue shifted (dv~500 km/s) absorber most likely represents material in the cavity between the out-flowing shell and the Ly-alpha halo. We estimate that the mass in the shell must be of order 10^10 Msol -- a significant fraction of the ISM from a galaxy at z=4. The large scales of these coherent structures illustrate the potentially powerful influence of AGN feedback on the distribution and energetics of material in their surroundings. Indeed, the discovery of high-velocity (~1000 km/s), group-halo-scale (i.e. >150 kpc) and mass-loaded winds in the vicinity of the central radio source are broadly in agreement with the requirements of models that invoke AGN-driven outflows to regulate star formation and black-hole growth in massive galaxies at early times.
We present a study of the galaxy environment of 9 strong HI+CIV absorption line systems ($16.2<{rm log}(N({rm HI}))<21.2$) spanning a wide range in metallicity at $zsim4-5$, using MUSE integral field and X-Shooter spectroscopic data collected in a $z
approx 5.26$ quasar field. We identify galaxies within a 250 kpc and $pm1000$ km s$^{-1}$ window for 6 out of the 9 absorption systems, with 2 of the absorption line systems showing multiple associated galaxies within the MUSE field of view. The space density of Ly$alpha$ emitting galaxies (LAEs) around the HI and CIV systems is $approx10-20$ times the average sky density of LAEs given the flux limit of our survey, showing a clear correlation between the absorption and galaxy populations. Further, we find that the strongest CIV systems in our sample are those that are most closely aligned with galaxies in velocity space, i.e. within velocities of $pm500$ km s$^{-1}$. The two most metal poor systems lie in the most dense galaxy environments, implying we are potentially tracing gas that is infalling for the first time into star-forming groups at high redshift. Finally, we detect an extended Ly$alpha$ nebula around the $zapprox 5.26$ quasar, which extends up to $approx50$ kpc at the surface brightness limit of $3.8 times 10^{-18}$ erg s$^{-1}$ cm$^{-2}$ arcsec$^{-2}$. After scaling for surface brightness dimming, we find that this nebula is centrally brighter, having a steeper radial profile than the average for nebulae studied at $zsim3$ and is consistent with the mild redshift evolution seen from $zapprox 2$.
We present spectroscopic observations of six high redshift ($z_{rm em}$ $>$ 2) quasars, which have been selected for their Lyman $alpha$ (Ly$alpha$) emission region being only partially covered by a strong proximate ($z_{rm abs}$ $sim$ $z_{rm em}$) c
oronagraphic damped Ly$alpha$ system (DLA). We detected spatially extended Ly$alpha$ emission envelopes surrounding these six quasars, with projected spatial extent in the range 26 $le$ $d_{rm Lyalpha}$ $le$ 51 kpc. No correlation is found between the quasar ionizing luminosity and the Ly$alpha$ luminosity of their extended envelopes. This could be related to the limited covering factor of the extended gas and/or due to the AGN being obscured in other directions than towards the observer. Indeed, we find a strong correlation between the luminosity of the envelope and its spatial extent, which suggests that the envelopes are probably ionized by the AGN. The metallicity of the coronagraphic DLAs is low and varies in the range $-$1.75 $<$ [Si/H] $<$ $-$0.63. Highly ionized gas is observed to be associated with most of these DLAs, probably indicating ionization by the central AGN. One of these DLAs has the highest AlIII/SiII ratio ever reported for any intervening and/or proximate DLA. Most of these DLAs are redshifted with respect to the quasar, implying that they might represent infalling gas probably accreted onto the quasar host galaxies through filaments.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
