arXiv subjects

Iván Oteo

Publications and source records attributed to Iván Oteo.

6 recordsLinked to original sources

arXiv2018

Flat Rotation Curves found in Merging Dusty Starbursts at $z=2.3$ through Tilted-Ring Modeling

The brightest 500$\,μ$m source in the XMM field, HXMM01, is a rare merger of luminous starburst galaxies at $z=2.3$ with a dust-obscured star-formation rate of 2,000$\,M_{\odot}\,{\rm yr}^{-1}$. Here we present high-resolution spectroscopic observations of HXMM01 with the Atacama Large Millimeter/submillimeter Array (ALMA). We detect line emission from ${\rm CO\,{\it J}=7\to6}$, [C I]$\,{{^3P_2}\to{^3P_1}}$, and p-${\rm H_{2}O}\,{2_{11}}\to{2_{02}}$ and continuum emission at $230\,$GHz. At a spatial resolution of 0.2" and a spectral resolution of 40$\,\rm km\,s^{-1}$, the source is resolved into three distinct components, which are spatially and dynamically associated within a projected radius of 20$\,$kpc and a radial velocity range of 2,000$\,\rm km\,s^{-1}$. For two major components, our Bayesian-based tilted-ring modeling of the ALMA spectral cubes shows almost flat rotation curves peaking at $\sim500\,\rm km\,s^{-1}$ at galactocentric distances between 2 and 5$\,$kpc. Each of them has a dynamical mass of $\sim10^{11}\,M_\odot$. The combination of the dynamical masses and the archival ${\rm CO\,{\it J}=1\to0}$ data places strong upper limits on the CO$\to$H$_2$ conversion factor of $α_{\rm CO}\lesssim1.4-2.0\,{M_{\odot}}\,\rm (K\,km\,s^{-1}\,pc^{2})^{-1}$. These limits are significantly below the Galactic inner disk $α_{\rm CO}$ value of $4.3\,{M_{\odot}}\,\rm (K\,km\,s^{-1}\,pc^{2})^{-1}$ but are consistent with those of local starbursts. Therefore, the previously estimated short gas depletion timescale of $\sim200\,$Myr remains unchanged.

astro-ph.GA↗

arXiv2018

The nature of luminous Lyman-alpha emitters at z~2-3: maximal dust-poor starbursts and highly ionising AGN

Deep narrow-band surveys have revealed a large population of faint Lyman-alpha (Lya) emitters (LAEs) in the distant Universe, but relatively little is known about the most luminous sources ($L_{Lyα}>10^{42.7}$ erg/s; $L_{Lyα}>L^*_{Lyα}$). Here we present the spectroscopic follow-up of 21 luminous LAEs at z~2-3 found with panoramic narrow-band surveys over five independent extragalactic fields (~4x10$^6$ Mpc$^{3}$ surveyed at z~2.2 and z~3.1). We use WHT/ISIS, Keck/DEIMOS and VLT/X-SHOOTER to study these sources using high ionisation UV lines. Luminous LAEs at z~2-3 have blue UV slopes ($β=-2.0^{+0.3}_{-0.1}$), high Lya escape fractions ($50^{+20}_{-15}$%) and span five orders of magnitude in UV luminosity ($M_{UV}\approx-19$ to -24). Many (70%) show at least one high ionisation rest-frame UV line such as CIV, NV, CIII], HeII or OIII], typically blue-shifted by ~100-200 km/s relative to Lya. Their Lya profiles reveal a wide variety of shapes, including significant blue-shifted components and widths from 200 to 4000 km/s. Overall, 60+-11% appear to be AGN dominated, and at $L_{Lyα}>10^{43.3}$ erg/s and/or $M_{UV}<-21.5$ virtually all LAEs are AGN with high ionisation parameters (log U=0.6+-0.5) and with metallicities of ~0.5-1 Zsun. Those lacking signatures of AGN (40+-11%) have lower ionisation parameters ($\log U=-3.0^{+1.6}_{-0.9}$ and $\logξ_{\rm ion}=25.4\pm0.2$) and are apparently metal-poor sources likely powered by young, dust-poor "maximal" starbursts. Our results show that luminous LAEs at z~2-3 are a diverse population and that 2xL$^*_{Lyα}$ and 2xM$_{UV}^*$ mark a sharp transition in the nature of LAEs, from star formation dominated to AGN dominated.

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arXiv2016

The CALYMHA survey: Lya luminosity function and global escape fraction of Lya photons at z=2.23

We present the CAlibrating LYMan-$α$ with H$α$ (CALYMHA) pilot survey and new results on Lyman-$α$ (Lya) selected galaxies at z~2. We use a custom-built Lya narrow-band filter at the Isaac Newton Telescope, designed to provide a matched volume coverage to the z=2.23 Ha HiZELS survey. Here we present the first results for the COSMOS and UDS fields. Our survey currently reaches a 3$σ$ line flux limit of ~4x10$^{-17}$ erg/s/cm$^{2}$, and a Lya luminosity limit of ~10$^{42.3}$ erg/s. We find 188 Lya emitters over 7.3x10$^5$ Mpc$^{3}$, but also find significant numbers of other line emitting sources corresponding to HeII, CIII] and CIV emission lines. These sources are important contaminants, and we carefully remove them, unlike most previous studies. We find that the Lya luminosity function at z=2.23 is very well described by a Schechter function up to L~10$^{43}$ erg/s with L$^*=10^{42.59+-0.05}$ erg/s, $ϕ^*=10^{-3.09+-0.08}$ Mpc$^{-3}$ and $α$=-1.75+-0.15. Above L~10$^{43}$ erg/s the Lya luminosity function becomes power-law like, driven by X-ray AGN. We find that Lya-selected emitters have a high escape fraction of 37+-7%, anti-correlated with Lya luminosity and correlated with Lya equivalent width. Lya emitters have ubiquitous large (~40 kpc) Lya haloes, 2x larger than their Ha extents. By directly comparing our Lya and Ha luminosity functions we find that the global/overall escape fraction of Lya photons (within a 13 kpc radius) from the full population of star-forming galaxies is 5.1+-0.2% at the peak of the star formation history. An extra 3.3+-0.3% of Lya photons likely still escape, but at larger radii.

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arXiv2016

Multi-wavelength lens reconstruction of a $\textit{Planck}$ $\&$ $\textit{Herschel}$-detected star-bursting galaxy

We present a source-plane reconstruction of a ${\it Herschel}$ and ${\it Planck}$-detected gravitationally-lensed dusty star-forming galaxy (DSFG) at $z=1.68$ using {\it Hubble}, Sub-millimeter Array (SMA), and Keck observations. The background sub-millimeter galaxy (SMG) is strongly lensed by a foreground galaxy cluster at $z=0.997$ and appears as an arc of length $\sim 15^{\prime \prime}$ in the optical images. The continuum dust emission, as seen by SMA, is limited to a single knot within this arc. We present a lens model with source plane reconstructions at several wavelengths to show the difference in magnification between the stars and dust, and highlight the importance of a multi-wavelength lens models for studies involving lensed DSFGs. We estimate the physical properties of the galaxy by fitting the flux densities to model SEDs leading to a magnification-corrected star formation rate of $390 \pm 60$ M$_{\odot}$ yr$^{-1}$ and a stellar mass of $1.1 \pm 0.4\times 10^{11}$ M$_{\odot}$. These values are consistent with high-redshift massive galaxies that have formed most of their stars already. The estimated gas-to-baryon fraction, molecular gas surface density, and SFR surface density have values of $0.43 \pm 0.13$, $350 \pm 200$ M$_{\odot}$ pc$^{-2}$, and $\sim 12 \pm 7~$M$_{\odot}$ yr$^{-1}$ kpc$^{-2}$, respectively. The ratio of star formation rate surface density to molecular gas surface density puts this among the most star-forming systems, similar to other measured SMGs and local ULIRGS.

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arXiv2015

San Pedro Martir observations of microvariability in obscured quasars

Fast brightness variations are a unique tool to probe the innermost regions of active galactic nuclei (AGN). These variations are called microvariability or intra-night variability, and this phenomenon has been monitored in samples of blazars and unobscured AGNs. Detecting optical microvariations in targets hidden by the obscuring torus is a challenging task because the region responsible for the variations is hidden from our sight. However, there have been reports of fast variations in obscured Seyfert galaxies in X-rays, which rises the question whether microvariations can also be detected in obscured AGNs in the optical regime. Because the expected variations are very small and can easily be lost within the noise, the analysis requires a statistical approach. We report the use of a one-way analysis of variance, ANOVA, with which we searched for microvariability. ANOVA was successfully employed in previous studies of unobscured AGNs. As a result, we found microvariable events during three observing blocks: in two we observed the same object (Mrk 477), and in another, J0759+5050. The results on Mrk 477 confirm previous findings. However, since Mrk 477 is quite a peculiar target with hidden broad-line regions, we cannot rule out the possibility that we have serendipitously chosen a target prone to variations.

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arXiv2015

GLACE survey: OSIRIS/GTC Tuneable Filter H$α$ imaging of the rich galaxy cluster ZwCl 0024.0+1652 at z = 0.395. Part I -- Survey presentation, TF data reduction techniques and catalogue

The cores of clusters at 0 $\lesssim$ z $\lesssim$ 1 are dominated by quiescent early-type galaxies, whereas the field is dominated by star-forming late-type ones. Galaxy properties, notably the star formation (SF) ability, are altered as they fall into overdense regions. The critical issues to understand this evolution are how the truncation of SF is connected to the morphological transformation and the responsible physical mechanism. The GaLAxy Cluster Evolution Survey (GLACE) is conducting a study on the variation of galaxy properties (SF, AGN, morphology) as a function of environment in a representative sample of clusters. A deep survey of emission line galaxies (ELG) is being performed, mapping a set of optical lines ([OII], [OIII], H$β$ and H$α$/[NII]) in several clusters at z $\sim$ 0.40, 0.63 and 0.86. Using the Tunable Filters (TF) of OSIRIS/GTC, GLACE applies the technique of TF tomography: for each line, a set of images at different wavelengths are taken through the TF, to cover a rest frame velocity range of several thousands km/s. The first GLACE results target the H$α$/[NII] lines in the cluster ZwCl 0024.0+1652 at z = 0.395 covering $\sim$ 2 $\times$ r$_{vir}$. We discuss the techniques devised to process the TF tomography observations to generate the catalogue of H$α$ emitters of 174 unique cluster sources down to a SFR below 1 M$_{\odot}$/yr. The AGN population is discriminated using different diagnostics and found to be $\sim$ 37% of the ELG population. The median SFR is 1.4 M$_{\odot}$/yr. We have studied the spatial distribution of ELG, confirming the existence of two components in the redshift space. Finally, we have exploited the outstanding spectral resolution of the TF to estimate the cluster mass from ELG dynamics, finding M$_{200}$ = 4.1 $\times$ 10$^{14}$ M$_{\odot} h^{-1}$, in agreement with previous weak-lensing estimates.

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