arXiv subjects

I. Oteo

Publications and source records attributed to I. Oteo.

52 records · Page 3Linked to original sources

arXiv2015

Spitzer Imaging of Strongly-Lensed Herschel-Selected Dusty Star Forming Galaxies

We present the rest-frame optical spectral energy distribution and stellar masses of six Herschel- selected gravitationally lensed dusty, star-forming galaxies (DSFGs) at 1 < z < 3. These galaxies were first identified with Herschel/SPIRE imaging data from the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS) and the Herschel Multi-tiered Extragalactic Survey (HerMES). The targets were observed with Spitzer/IRAC at 3.6 and 4.5um. Due to the spatial resolution of the IRAC observations at the level of 2 arcseconds, the lensing features of a background DSFG in the near-infrared are blended with the flux from the foreground lensing galaxy in the IRAC imaging data. We make use of higher resolution Hubble/WFC3 or Keck/NIRC2 Adaptive Optics imaging data to fit light profiles of the foreground lensing galaxy (or galaxies) as a way to model the foreground components, in order to successfully disentangle the foreground lens and background source flux densities in the IRAC images. The flux density measurements at 3.6 and 4.5um, once combined with Hubble/WFC3 and Keck/NIRC2 data, provide important constraints on the rest-frame optical spectral energy distribution of the Herschel-selected lensed DSFGs. We model the combined UV- to millimeter-wavelength SEDs to establish the stellar mass, dust mass, star-formation rate, visual extinction, and other parameters for each of these Herschel-selected DSFGs. These systems have inferred stellar masses in the range 8 x 10^10 to 4 x 10^11 Msun and star-formation rates of around 100 Msun yr-1. This puts these lensed sub-millimeter systems well above the SFR-M* relation observed for normal star-forming galaxies at similar redshifts. The high values of SFR inferred for these systems are consistent with a major merger-driven scenario for star formation.

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arXiv2015

Extinction and nebular line properties of a Herschel-selected lensed dusty starburst AT z=1.027

We present Hubble Space Telescope (HST) WFC3 imaging and grism spectroscopy observations of the {\it Herschel}-selected gravitationally-lensed starburst galaxy HATLASJ1429-0028. The lensing system consists of an edge-on foreground disk galaxy at $z=0.218$ with a nearly complete Einstein ring of the infrared luminous galaxy at $z=1.027$. The WFC3 spectroscopy with G102 and G141 grisms, covering the wavelength range of 0.8 to 1.7 $μ$m, resulted in detections of H$α$+[NII], H$β$, [SII], and [OIII] for the background galaxy from which we measure line fluxes and ratios. The Balmer line ratio H$α$/H$β$ of $7.5 \pm 4.4$, when corrected for [NII], results in an extinction for the starburst galaxy of $E(B-V)=0.8 \pm 0.5$. The $Hα$ based star-formation rate, when corrected for extinction, is $60 \pm 50$ M$_{\odot}$ yr$^{-1}$, lower than the instantaneous star-formation rate of 390 $\pm$ 90 M$_{\odot}$ yr$^{-1}$ from the total IR luminosity. We also compare the nebular line ratios of HATLASJ1429-0028 with other star-forming and sub-mm bright galaxies. The nebular line ratios are consistent with an intrinsic ultra-luminous infrared galaxy with no evidence for excitation by an active galactic nucleus (AGN). We estimate the metallicity, $12 + log(O/H)$, of HATLASJ1429-0028 to be 8.49 $\pm$ 0.16. Such a low value is below the average relations for stellar mass vs. metallicity of galaxies at $z \sim 1$ for a galaxy with stellar mass of $\sim 2 \times 10^{11}$ M$_{\odot}$. The combination of high stellar mass, lack of AGN indicators, low metallicity, and the high star-formation rate of HATLASJ1429-0028 suggest that this galaxy is currently undergoing a rapid formation.

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arXiv2015

High redshift galaxies in the ALHAMBRA survey: I. selection method and number counts based on redshift PDFs

Context. Most observational results on the high redshift restframe UV-bright galaxies are based on samples pinpointed using the so called dropout technique or Ly-alpha selection. However, the availability of multifilter data allows now replacing the dropout selections by direct methods based on photometric redshifts. In this paper we present the methodology to select and study the population of high redshift galaxies in the ALHAMBRA survey data. Aims. Our aim is to develop a less biased methodology than the traditional dropout technique to study the high redshift galaxies in ALHAMBRA and other multifilter data. Thanks to the wide area ALHAMBRA covers, we especially aim at contributing in the study of the brightest, less frequent, high redshift galaxies. Methods. The methodology is based on redshift probability distribution functions (zPDFs). It is shown how a clean galaxy sample can be obtained by selecting the galaxies with high integrated probability of being within a given redshift interval. However, reaching both a complete and clean sample with this method is challenging. Hence, a method to derive statistical properties by summing the zPDFs of all the galaxies in the redshift bin of interest is introduced. Results. Using this methodology we derive the galaxy rest frame UV number counts in five redshift bins centred at z=2.5, 3.0, 3.5, 4.0, and 4.5, being complete up to the limiting magnitude at m_UV(AB)=24. With the wide field ALHAMBRA data we especially contribute in the study of the brightest ends of these counts, sampling well the surface densities down to m_UV(AB)=21-22. Conclusions. We show that using the zPDFs it is easy to select a clean sample of high redshift galaxies. We also show that statistical analysis of the properties of galaxies is better done using a probabilistic approach, which takes into account both the incompleteness and contamination in a natural way.

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arXiv2014

Dust correction factors over $0 < z < 3$ in massive star-forming galaxies from stacking in \emph{Herschel}

In this work we use stacking analysis in \emph{Herschel} PACS to study the accuracy of several dust-correction factors typically employed to estimate total star-formation rate (SFR) of high-redshift star-forming (SF) galaxies. We also analyze what stacking suggests about the relation between SFR and stellar mass and the redshift evolution of the specific SFR (${\rm sSFR} = {\rm SFR} / {\rm M_*}$). We find that the dust properties of massive SF galaxies evolve with redshift, being galaxies at $z \sim 2-3$ more attenuated than at $z \sim 1$ for a given UV continuum slope and stellar mass. As a consequence, a single IRX-$β$ relation can not be used to recover the total SFR of massive SF galaxies at $0 \lesssim z \lesssim 3$. This might have implications for higher redshift studies, where a single IRX-$β$ relation derived for local starburst is usually assumed to be valid. However, we find that the local relation between dust attenuation and stellar mass is valid at least up to $z \sim 1$, although deviations are found for higher redshift galaxies where only $\log{\left( M_* / M_\odot \right)} > 10.25-10.50$ galaxies are detected through stacking. This, therefore, does not rule out the possibility that the local dust-mass relation can be valid for less massive SF galaxies at $z \sim 2-3$. The SED fitting procedure with stellar population templates gives over-estimated values (about 0.3--0.5 dex in $\log{\rm SFR}$) of the dust-corrected SFR at all redshifts studied here. We find that the slope of the main-sequence of star formation is less steep than previously found in massive galaxies with $\log{\left( M_* / M_\odot \right)} \geq 10$, and the redshift evolution of the sSFR reported in previous works in massive is well recovered.

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arXiv2014

J-PAS: The Javalambre-Physics of the Accelerated Universe Astrophysical Survey

The Javalambre-Physics of the Accelerated Universe Astrophysical Survey (J-PAS) is a narrow band, very wide field Cosmological Survey to be carried out from the Javalambre Observatory in Spain with a purpose-built, dedicated 2.5m telescope and a 4.7 sq.deg. camera with 1.2Gpix. Starting in late 2015, J-PAS will observe 8500sq.deg. of Northern Sky and measure $0.003(1+z)$ photo-z for $9\times10^7$ LRG and ELG galaxies plus several million QSOs, sampling an effective volume of $\sim 14$ Gpc$^3$ up to $z=1.3$ and becoming the first radial BAO experiment to reach Stage IV. J-PAS will detect $7\times 10^5$ galaxy clusters and groups, setting constrains on Dark Energy which rival those obtained from its BAO measurements. Thanks to the superb characteristics of the site (seeing ~0.7 arcsec), J-PAS is expected to obtain a deep, sub-arcsec image of the Northern sky, which combined with its unique photo-z precision will produce one of the most powerful cosmological lensing surveys before the arrival of Euclid. J-PAS unprecedented spectral time domain information will enable a self-contained SN survey that, without the need for external spectroscopic follow-up, will detect, classify and measure $σ_z\sim 0.5\%$ redshifts for $\sim 4000$ SNeIa and $\sim 900$ core-collapse SNe. The key to the J-PAS potential is its innovative approach: a contiguous system of 54 filters with $145Å$ width, placed $100Å$ apart over a multi-degree FoV is a powerful "redshift machine", with the survey speed of a 4000 multiplexing low resolution spectrograph, but many times cheaper and much faster to build. The J-PAS camera is equivalent to a 4.7 sq.deg. "IFU" and it will produce a time-resolved, 3D image of the Northern Sky with a very wide range of Astrophysical applications in Galaxy Evolution, the nearby Universe and the study of resolved stellar populations.

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arXiv2014

Herschel Far-IR counterparts of SDSS galaxies: Analysis of commonly used Star Formation Rate estimates

We study a hundred of galaxies from the spectroscopic Sloan Digital Sky Survey with individual detections in the Far-Infrared Herschel PACS bands (100 or 160 $μ$m) and in the GALEX Far-UltraViolet band up to z$\sim$0.4 in the COSMOS and Lockman Hole fields. The galaxies are divided into 4 spectral and 4 morphological types. For the star forming and unclassifiable galaxies we calculate dust extinctions from the UV slope, the H$α$/H$β$ ratio and the $L_{\rm IR}/L_{\rm UV}$ ratio. There is a tight correlation between the dust extinction and both $L_{\rm IR}$ and metallicity. We calculate SFR$_{total}$ and compare it with other SFR estimates (H$α$, UV, SDSS) finding a very good agreement between them with smaller dispersions than typical SFR uncertainties. We study the effect of mass and metallicity, finding that it is only significant at high masses for SFR$_{Hα}$. For the AGN and composite galaxies we find a tight correlation between SFR and L$_{IR}$ ($σ\sim$0.29), while the dispersion in the SFR - L$_{UV}$ relation is larger ($σ\sim$0.57). The galaxies follow the prescriptions of the Fundamental Plane in the M-Z-SFR space.

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arXiv2013

The UV to FIR spectral energy distribution of star-forming galaxies in the redshift desert

We analyse the rest-frame UV-to-NIR spectral energy distribution (SED) of Lyman break galaxies (LBGs), star-forming (SF) BzK (sBzK), and UV-selected galaxies at 1.5 < z < 2.5 in the COSMOS, GOODS-N, and GOODS-S fields. Additionally, we complement the multi-wavelength coverage of the galaxies located in the GOODS fields with deep FIR data taken from the GOODS-Herschel project. We find that sBzK galaxies represent the general population of SF galaxies at z ~ 2 better than LBGs. For a given stellar mass, LBGs tend to have bluer optical colours than sBzK and UV-selected galaxies. We find clean PACS individual detections for a subsample of 48 LBGs, 89 sBzK, and 91 UV-selected galaxies, that measure their dust emission directly. Their SFR_total = SFR_UV + SFR_IR cannot be recovered with the dust-correction factors derived with their continuum slope and the IRX-beta relations for local starbursts. This has implications, for example, in the definition of the main sequence (MS) at z ~ 2. PACS-detected galaxies are located above the z ~ 2 MS and thus their star formation is probably driven by starburst. This is in agreement with the shape of their IR SEDs. PACS-detected galaxies with redder UV continuum slope and higher stellar mass are more attenuated. We find that for a given UV continuum slope the dustiest galaxies at higher redshifts are more attenuated and that for a given stellar mass the dustiest galaxies at higher redshifts have stronger FIR emission. This suggests an evolution of their dust properties. However, we do not find significant evolution in the relation between dust attenuation and stellar mass with redshift, at least at z < 2.5. There is a subpopulation of 17, 26, and 27 LBGs, sBzK, and UV-selected galaxies, respectively, that are detected in any of the SPIRE bands. We speculate that SPIRE-detected LBGs are the bridging population between sub-mm galaxies and LBGs.

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arXiv2013

Multi-wavelength landscape of the young galaxy cluster RXJ1257.2+4738 at z=0.866: I. The infrared view

We performed a thorough analysis of the star formation activity in the young massive galaxy cluster RXJ1257+4738 at z=0.866, with emphasis on the relationship between the local environment of the cluster galaxies and their star formation activity. We present an optical and IR study that benefited from the large amount of data available for this cluster, including new OSIRIS/GTC and Herschel imaging observations. Using a optical-to-NIR multi-wavelength catalogue, we measured photometric redshifts through a chi2 SED-fitting procedure. We implemented a reliable and carefully chosen cluster membership selection criterion including Monte Carlo simulations and derived a sample of 292 reliable cluster member galaxies for which we measured the following properties: optical colours, stellar masses, ages, ultraviolet luminosities and local densities. Using the MIPS 24um and Herschel data, we measured total IR luminosities and SFR. Of the sample of 292 cluster galaxies, 38 show FIR emission with an SFR between 0.5 and 45 Msun/yr. The spatial distribution of the FIR emitters within the cluster density map and the filament-like overdensities observed suggest that RXJ1257 is not virialised, but is in the process of assembly. The average star formation as a function of the cluster environment parametrised by the local density of galaxies does not show any clear trend. However, the fraction of SF galaxies unveils that the cluster intermediate-density regions is preferred for the SF activity to enhance, since we observe a significant increase of the FIR-emitter fraction in this environment. Focusing on the optically red SF galaxies, we can support the interpretation of this population as dusty red galaxies, since we observe an appreciable difference in their extinction compared with the blue population.

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arXiv2013

The ALHAMBRA survey: reliable morphological catalogue of 22,051 early- and late-type galaxies

ALHAMBRA is a photometric survey designed to trace the cosmic evolution and cosmic variance. It covers a large area of ~ 4 sq. deg in 8 fields, where 7 fields overlap with other surveys, allowing to have complementary data in other wavelengths. All observations were carried out in 20 continuous, medium band (30 nm width) optical and 3 near-infrared (JHK) bands, providing the precise measurements of photometric redshifts. In addition, morphological classification of galaxies is crucial for any kind of galaxy formation and cosmic evolution studies, providing the information about star formation histories, their environment and interactions, internal perturbations, etc. We present a morphological classification of > 40,000 galaxies in the ALHAMBRA survey. We associate to every galaxy a probability to be early-type using the automated Bayesian code galSVM. Despite of the spatial resolution of the ALHAMBRA images (~ 1 arcsec), for 22,051 galaxies we obtained the contamination by other type of less than 10%. Of those, 1,640 and 10,322 galaxies are classified as early- (down to redshifts ~ 0.5) and late-type (down to redshifts ~ 1.0), respectively, with magnitudes F613W < 22.0. In addition, for magnitude range 22.0 < F613W < 23.0 we classified other 10,089 late-type galaxies with redshifts < 1.3. We show that the classified objects populate the expected regions in the colour-mass and colour-magnitude planes. The presented dataset is especially attractive given the homogeneous multi-wavelength coverage available in the ALHAMBRA fields, and is intended to be used in a variety of scientific applications. The low-contamination catalogue (< 10%) is made publicly available with the present paper.

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arXiv2013

Lyman break and UV-selected galaxies at z ~ 1: II. PACS-100um/160um FIR detections

We report the PACS-100um/160um detections of a sample of 42 GALEX-selected and FIR-detected Lyman break galaxies (LBGs) at z ~ 1 located in the COSMOS field and analyze their ultra-violet (UV) to far-infrared (FIR) properties. The detection of these LBGs in the FIR indicates that they have a dust content high enough so that its emission can be directly detected. According to a spectral energy distribution (SED) fitting with stellar population templates to their UV-to-near-IR observed photometry, PACS-detected LBGs tend to be bigger, more massive, dustier, redder in the UV continuum, and UV-brighter than PACS-undetected LBGs. PACS-detected LBGs at z ~ 1 are mostly disk-like galaxies and are located over the green-valley and red sequence of the color-magnitude diagram of galaxies at their redshift. By using their UV and IR emission, we find that PACS-detected LBGs tend to be less dusty and have slightly higher total star-formation rates (SFRs) than other PACS-detected UV-selected galaxies within their same redshift range. As a consequence of the selection effect due to the depth of the FIR observations employed, all our PACS-detected LBGs are LIRGs. However, none of them are in the ULIRG regime, where the FIR observations are complete. The finding of ULIRGs-LBGs at higher redshifts suggests an evolution of the FIR emission of LBGs with cosmic time. In an IRX-$β$ diagram, PACS-detected LBGs at z ~ 1 tend to be located around the relation for local starburst similarly to other UV-selected PACS-detected galaxies at their same redshift. Consequently, the dust-correction factors obtained with their UV continuum slope allow to determine their total SFR, unlike at higher redshifts. However, the dust attenuation derived from UV to NIR SED fitting overestimates the total SFR for most of our PACS-detected LBGs in age-dependent way: the overestimation factor is higher in younger galaxies.

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arXiv2013

Lyman break and UV-selected galaxies at $z \sim 1$ I. Stellar populations from ALHAMBRA survey

We take advantage of the exceptional photometric coverage provided by the combination of GALEX data in the UV and the ALHAMBRA survey in the optical and near-IR to analyze the physical properties of a sample of 1225 GALEX-selected Lyman break galaxies (LBGs) at $0.8 \lesssim z \lesssim 1.2$ located in the COSMOS field. This is the largest sample of LBGs studied at that redshift range so far. According to a spectral energy distribution (SED) fitting with synthetic stellar population templates, we find that LBGs at $z \sim 1$ are mostly young galaxies with a median age of 341 Myr and have intermediate dust attenuation, $\ < E_s (B-V) \ > \sim 0.20$. Due to their selection criterion, LBGs at $z \sim 1$ are UV-bright galaxies and have high dust-corrected total SFR, with a median value of 16.9 $M_\odot {\rm yr}^{-1}$. Their median stellar mass is $\log{\left(M_*/M_\odot \right)} = 9.74$. We obtain that the dust-corrected total SFR of LBGs increases with stellar mass and the specific SFR is lower for more massive galaxies. Only 2% of the galaxies selected through the Lyman break criterion have an AGN nature. LBGs at $z \sim 1$ are mostly located over the blue cloud of the color-magnitude diagram of galaxies at their redshift, with only the oldest and/or the dustiest deviating towards the green valley and red sequence. Morphologically, 69% of LBGs are disk-like galaxies, with the fraction of interacting, compact, or irregular systems being much lower, below 12%. LBGs have a median effective radius of 2.5 kpc and bigger galaxies have higher total SFR and stellar mass. Comparing to their high-redshift analogues, we find evidence that LBGs at lower redshifts are bigger, redder in the UV continuum, and have a major presence of older stellar populations in their SEDs. However, we do not find significant difference in the distributions of stellar mass or dust attenuation.

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arXiv2013

FIR-detected Lyman break galaxies at z ~ 3: Dust attenuation and dust correction factors at high redshift

Lyman break galaxies (LBGs) represent one of the kinds of star-forming galaxies that are found in the high-redshift universe. The detection of LBGs in the FIR domain can provide very important clues on their dust attenuation and total SFR, allowing a more detailed study than those performed so far. In this work we explore the FIR emission of a sample of 16 LBGs at z ~ 3 in the GOODS-North and GOODS-South fields that are individually detected in PACS-100um or PACS-160um. These detections demonstrate the possibility of measuring the dust emission of LBGs at high redshift. We find that PACS-detected LBGs at z ~ 3 are highly obscured galaxies which belong to the Ultra luminous IR galaxies or Hyper luminous IR galaxies class. Their total SFR cannot be recovered with the dust attenuation factors obtained from their UV continuum slope or their SED-derived dust attenuation employing Bruzual & Charlot (2003) templates. Both methods underestimate the results for most of the galaxies. Comparing with a sample of PACS-detected LBGs at z ~ 1 we find evidences that the FIR emission of LBGs might have changed with redshift in the sense that the dustiest LBGs found at z ~ 3 have more prominent FIR emission, are dustier for a given UV slope, and have higher SFR for a given stellar mass than the dustiest LBGs found at z ~ 1.

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arXiv2012

Physical properties of Lyman-alpha emitters at $z\sim 0.3$ from UV-to-FIR measurements

The analysis of the physical properties of low-redshift Ly$α$ emitters (LAEs) can provide clues in the study of their high-redshift analogues. At $z \sim 0.3$, LAEs are bright enough to be detected over almost the entire electromagnetic spectrum and it is possible to carry out a more precise and complete study than at higher redshifts. In this study, we examine the UV and IR emission, dust attenuation, SFR and morphology of a sample of 23 GALEX-discovered star-forming (SF) LAEs at $z \sim 0.3$ with direct UV (GALEX), optical (ACS) and FIR (PACS and MIPS) data. Using the same UV and IR limiting luminosities, we find that LAEs at $z\sim 0.3$ tend to be less dusty, have slightly higher total SFRs, have bluer UV continuum slopes, and are much smaller than other galaxies that do not exhibit Ly$α$ emission in their spectrum (non-LAEs). These results suggest that at $z \sim 0.3$ Ly$α$ photons tend to escape from small galaxies with low dust attenuation. Regarding their morphology, LAEs belong to Irr/merger classes, unlike non-LAEs. Size and morphology represent the most noticeable difference between LAEs and non-LAEs at $z \sim 0.3$. Furthermore, the comparison of our results with those obtained at higher redshifts indicates that either the Ly$α$ technique picks up different kind of galaxies at different redshifts or that the physical properties of LAEs are evolving with redshift.

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arXiv2012

PACS-Herschel FIR detections of Lyman-alpha emitters at 2.0<z<3.5

In this work we analyze the physical properties of a sample of 56 spectroscopically selected star-forming (SF) Ly$α$ emitting galaxies at 2.0$\lesssim$z$\lesssim$3.5 using both a spectral energy distribution (SED) fitting procedure from rest-frame UV to mid-IR and direct 160$μ$m observations taken with the Photodetector Array Camera & Spectrometer (PACS) instrument onboard \emph{Herschel Space Observatory}. We define LAEs as those Ly$α$ emitting galaxies whose rest-frame Ly$α$ equivalent widths (Ly$α$ EW$_{rest-frame}$) are above 20Å, the typical threshold in narrow-band searches. Ly$α$ emitting galaxies with Ly$α$ EW$_{rest-frame}$ are called non-LAEs. As a result of an individual SED fitting for each object, we find that the studied sample of LAEs contains galaxies with ages mostly below 100Myr and a wide variety of dust attenuations, SFRs, and stellar masses. The heterogeneity in the physical properties is also seen in the morphology, ranging from bulge-like galaxies to highly clumpy systems. In this way, we find that LAEs at 2.0$\lesssim$z$\lesssim$3.5 are very diverse, and do not have a bimodal nature, as suggested in previous works. Furthermore, the main difference between LAEs and non-LAEs is their dust attenuation, because LAEs are not as dusty as non-LAEs. On the FIR side, four galaxies of the sample (two LAEs and two non-LAEs) have PACS-FIR counterparts. Their total IR luminosity place all of them in the ULIRG regime and are all dusty objects, with A$_{1200}$$\gtrsim$4mag. This is an indication from direct FIR measurements that dust and Ly$α$ emission are not mutually exclusive. This population of red and dusty LAEs is not seen at z$\sim$0.3, suggesting an evolution with redshift of the IR nature of galaxies selected via their Ly$α$ emission.

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arXiv2011

FIR measurements of Ly-$α$ emitters at z$\lesssim$1.0: dust attenuation from PACS-\emph{Herschel}

One remaining open question regarding the physical properties of Ly$α$ emitters (LAEs) is their dust content and its evolution with redshift. The variety of results is large and with those reported by now is difficult to establish clear relations between dust, other fundamental parameters of galaxies (star-formation rate, metallicity or age) and redshift. In this Letter, we report \emph{Herschel} PACS-100$μ$m, PACS-160$μ$m and \emph{Spitzer} MIPS-24$μ$m detections of a sample of spectroscopically GALEX-selected LAEs at z$\sim$0.3 and $\sim$1.0. Five out of ten and one out of two LAEs are detected in, at least, one PACS band at z$\sim$0.3 and $\sim$1.0, respectively. These measurements have a great importance given that they allow us to quantify, for the first time, the dust content of LAEs from direct FIR observations. MIPS-24$μ$m detections allow us to determine IR properties of the PACS-undetected LAEs. We obtain that mid-IR/FIR detected star-forming (SF) LAEs at z$\sim$0.3 have dust content within 0.75$\lesssim$ $A_{1200Å}$ $\lesssim$2.0, with a median value of A$_{1200\textrmÅ}$$\sim$1.1. This range broadens out to 0.75$\lesssim$ $A_{1200Å}$ $\lesssim$2.5 when considering those LAEs at z$\sim$1.0. Only one SF LAE is undetected both in MIPS-24$μ$m and PACS, with $A_{1200Å}$ $\lesssim$0.75. These results seem to be larger than those reported for high-redshift LAEs and, therefore, although an evolutionary trend is not clearly seen, it could point out that low-redshift LAEs are dustier than high-redshift ones. However, the diverse methods used could introduce a systematic offset in the results.

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arXiv2010

Herschel FIR counterparts of selected Ly-alpha emitters at z~2.2. Fast evolution since z~3 or missed obscured AGNs?

Ly-alpha emitters (LAEs) are seen everywhere in the redshift domain from local to z~7. Far-infrared (FIR) counterparts of LAEs at different epochs could provide direct clues on dust content, extinction, and spectral energy distribution (SED) for these galaxies. We search for FIR counterparts of LAEs that are optically detected in the GOODS-North field at redshift z~2.2 using data from the Herschel Space Telescope with the Photodetector Array Camera and Spectrometer (PACS). The LAE candidates were isolated via color-magnitude diagram using the medium-band photometry from the ALHAMBRA Survey, ancillary data on GOODS-North, and stellar population models. According to the fitting of these spectral synthesis models and FIR/optical diagnostics, most of them seem to be obscured galaxies whose spectra are AGN-dominated. From the analysis of the optical data, we have observed a fraction of AGN or composite over source total number of ~0.75 in the LAE population at z~2.2, which is marginally consistent with the fraction previously observed at z=2.25 and even at low redshift (0.2<z<0.45), but significantly different from the one observed at redshift ~3, which could be compatible either with a scenario of rapid change in the AGN fraction between the epochs involved or with a non detection of obscured AGN in other z=2-3 LAE samples due to lack of deep FIR observations. We found three robust FIR (PACS) counterparts at z~2.2 in GOODS-North. This demonstrates the possibility of finding dust emission in LAEs even at higher redshifts.

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